Diamond and cemented carbide composite material

Abstract

A composite material comprising a continuous polycrystalline diamond matrix embedded with cemented carbide entities which are homogeneously distributed throughout; wherein the polycrystalline diamond matrix comprises diamond and binder; and wherein the cemented carbide entities comprise metal carbide and binder and a method for making the same.

Description

Field of invention

[0001] The present invention relates to a composite material comprising cemented carbide entities in a polycrystalline diamond matrix for use in mining or rock cutting applications or wear parts and a method for producing the same.Background art

[0002] PCD (poly crystalline diamond) is well known for being highly wear resistant, making it a popular choice for making industrial applications. However, for toughness demanding mining applications, such as inserts for percussive and rotary drilling (with the exception of oil and gas) or mechanical cutting, PCD works less well due to its brittle behaviour, which limits the lifespan of the inserts. Cemented carbide has a unique combination of high elastic modulus, high hardness, high compressive strength, high wear and abrasion resistance together with a good level of toughness. Therefore, cemented carbide is commonly used in products such as mining and cutting inserts. Cemented carbide comprises a hard ceramic (carbide) phase and a binder phase.

[0003] It is desirable to combine the high wear resistance of the PCD with the toughness of the cemented carbide. However, known composite materials comprising diamond and cemented carbide are not so well balanced regarding the wear resistance to toughness relation making them prone to breaking and unreliable when for example used for mining inserts.

[0004] The best performing prior art PCD-inserts used for percussive drilling have layers with different diamond concentrations in the domed region of the insert, however the problem with this is that it demands a rather complex manufacture procedure which makes the material very expensive. The problem to be solved is how to provide a new material that is able to provide high performance, having the optimal balance between hardness, toughness and thermal conductivity, without excessive manufacturing costs, where the properties of the material can be tailored to suit the application.

[0005] A further problem to be solved relates to limitations of diamond layer thickness. A binder, which is typically cobalt, is infiltrated into the diamond layer for structural stability either from the cemented carbide substrate or by adding fine-grained binder powder. When a cemented carbide substrate is used the infiltration into the diamond table is limited to around 2 mm and this therefore limits the thickness of the diamond layer that it is possible to produce. The addition of fine-grained binder powders is problematic as it is difficult to homogenously blend and is easily oxidised. Therefore, an additional problem to be solved is how to produce thicker diamond-based layers.DEFINITIONS

[0006] By "cemented carbide" is herein meant a material that comprises at least 50 wt% tungsten carbide, possibly other hard constituents common in the art of making cemented carbides and a metallic binder phase preferably selected from one or more of Fe, Co and Ni.

[0007] By "HPHT" is herein meant a "High Pressure High Temperature" process with pressures about at or above the diamond stable region (>50 kBar) and with temperatures of at least about 1000 C.

[0008] By "SCCG" is herein meant a sintered cemented carbide cluster with at least 10 tungsten carbide grains and a metallic binder preferable based on Co and / or Ni and Fe. Preferably, the SCCG are spherical.

[0009] By "cemented carbide entity" is herein meant a sintered cemented carbide granule which is embedded in the polycrystalline diamond matrix with d50 between 5 - 60 µm having a substantially spherical shape, containing at least 10 tungsten carbide grains and a metallic binder preferable based on Co and / or Ni and Fe.

[0010] By "homogenously distributed throughout" is herein meant that the cemented carbide entities are evenly distributed throughout the composite material and that no distinguishable pattern in the distribution of the cemented carbide entities can be seen.

[0011] Examples of distinguishable patterns could be a gradient in either size, volume or number of the cemented carbide entities or that the material contains satellite structures wherein there would be a plurality of the smaller entities surrounding a larger entity.Summary of the Invention

[0012] According to the first aspect of the present invention, there is a composite material comprising a continuous polycrystalline diamond matrix embedded with cemented carbide entities which are homogeneously distributed throughout; wherein the polycrystalline diamond matrix comprises diamond and binder; and wherein the cemented carbide entities comprise metal carbide and binder.

[0013] Advantageously, this provides a material having an optimal balance between hardness, toughness and thermal conductivity, therefore providing a material that is more reliable and less prone to chipping and breaking. Furthermore, the properties of both the cemented carbide entities and the surrounding polycrystalline diamond matrix can be tailored to suit the application the material is being used for. As the cemented carbide entities act as localized catalyst / binder emitter it is also possible to produce thicker diamond-based layers having a high diamond content.

[0014] A further aspect of the present invention relates to a method for making a material as described hereinbefore or hereinafter comprising the steps of: a) providing diamond having an average grain size (d50 diafeed ) between 0.8-30 µm; b) providing sintered cemented carbide granules (SCCG) having a diameter (d50 SCCGfeed ) of 5-60 µm and wherein d50 SCCGfeed / d50 diafeed is ≥2. c) blending the diamond with the SCCG to form a homogenous blend; d) placing the blend into preformed refractory metal cup; e) providing a refractory metal lid; or a pre-sintered or sintered cemented carbide base on top of the blend to close the cup; f) pre-compacting the blend in the refractory metal cup; g) surrounding the cup with a pressure media; h) inserting the pressure media surrounded cup into a high-pressure high temperature container; i) placing the above container in a high-pressure high temperature press and sintering at high pressure and high temperature to form a composite material.

[0015] Advantageously, this results a material having a polycrystalline diamond matrix with cemented carbide entities homogeneously embedded therein. Furthermore, this method provides a more homogenous blend which provides uniform properties throughout the volume of the material, higher powder density, reduced and more controllable shrinkage during HPHT sintering cycle which means that there is greater control over the final shape of the product being produced. Further, it means that the properties of material can be steered as required for a specific application.Brief description of drawings

[0016] A specific implementation of the present invention will now be described, by way of example only, and with reference to the accompanying drawings in which: Figures 1a and 1b are SEM images at x500 and x1000 magnification respectively that show the structure of the inventive sample C material. Figure 2 is an SEM image at x500 magnification of comparative sample A Figure 3 is an SEM image taken at x2000 magnification. Figure 4 is a schematic drawing of a mining insert. Detailed description

[0017] Figures 1a and 1b are SEM images at x500 and x1000 magnification respectively showing the composite material 2. The composite material 2 comprises a continuous polycrystalline diamond matrix 4 embedded with cemented carbide entities 6 which are homogeneously distributed throughout. The polycrystalline diamond matrix 4 comprises diamond and binder; and wherein the cemented carbide entities comprise metal carbide and binder.

[0018] Figures 1a and 1b clearly show the homogeneous distribution of the cemented carbide entities 6 in the polycrystalline diamond matrix 4.

[0019] In one embodiment the distribution of the cemented carbide entities 6 in the polycrystalline diamond matrix 4 is a normal distribution. In other words, there is a single modal distribution of the cemented carbide entities 6. In another embodiment, there may be a multi modal distribution of the cemented carbide entities 6.

[0020] The cemented carbide entities 6 are homogenously distributed throughout the polycrystalline diamond matrix 4 in three dimensions in terms of: the distance between the neighbouring cemented carbide entities 6 throughout the material; the volume of the polycrystalline diamond matrix 4 between the cemented carbide entities 6; the volume of the cemented carbide entities 6 throughout the material is homogenously distributed, meaning that the cemented carbide entities 6 are evenly distributed throughout the composite material 2 and that no distinguishable pattern in the distribution of the cemented carbide entities 6 can be seen. Examples of distinguishable patterns could be a gradient in either size, volume or number of the cemented carbide entities or that the material contains satellite structures wherein there would be a plurality of smaller entities surrounding a larger entity. This could be investigated by analysing SEM or LOM images with Image J of the ground, lapped and ion polished material. The ion polishing was conducted for at least 190 minutes at 6 V and for at least 20 minutes at 2V with a sample angle of 4 degrees and continuous rotation. Initially a calibration of the scale (pixels / µm) in the SEM images was made by first measuring the scale bar in the SEM-image using the straight-line measuring function in Image J. The obtained data from this measurement and the dimension of the scale bar in the SEM-image are then processed using the "Set scale" function to finalize the calibration. The SEM image was then converted to an 8 bit image format (unless already in a 8 bit image format). The homogeneity in of terms of the volume of the polycrystalline diamond matrix 4 between the cemented carbide entities 6, was investigated by assessing the size distribution of the polycrystalline diamond matrix 4 area segments between the cemented carbide entities 6. The area segments obtained is regarded to correspond to the volume segments. The scaled image in the 8 bit format of the material were filtered using the Gaussian blur function with default settings of Sigma (Radius) 2.00.

[0021] After this a binary image, with the objective to return both the diamond and the binder (Co) as white and the cemented carbide as black (background) was made using the auto-thresholding method "Minimum". Following this, the binary image was cleaned up with the "Open" command. As a next step, the Watershed command was used. Finally, to assess polycrystalline diamond matrix 4 area segments between the cemented carbide entities, the" analyse particles function" was employed with settings for Size of 0-Infinity, Circularity of 0.00-1.00, Show of Overlay Masks, Exclude on edges selected and Include holes not selected. The d99 and the d50 were calculated for the mentioned area segments, as well as, the d99 / d50 ratio. A lower d99 / d50 for the polycrystalline diamond matrix 4 area segments between the cemented carbide entities 6 shows a more homogenous distribution of the cemented carbide entities that are embedded in the polycrystalline diamond matrix. The homogeneity in of terms of that the volume of the cemented carbide entities 6 throughout the material is homogenously distributed, could be investigated by comparing SEM or LOM from an area near in the bulk of the material and an area near the surface. The area% of the cemented carbide phase obtained is regarded to correspond to the volume% of the cemented carbide phase. The difference between the volume of the cemented carbide granules in the area near the surface and the volume of cemented carbide entities in the area in the bulk of the material (i.e. ((highest value- lowest value) / Highest value)* 100) is less than 15%, preferably less than 10%. By an "area near the surface" is defined as about 1 / 10th of the distance from the surface (i.e. the cutting edge) and by an "area in the bulk of the material" is defined as being about 1 / 10th of the distance from the substrate if there is a substrate present or about 1 / 10th of the distance from the bottom of the insert if there is no substrate present.

[0022] In some example embodiments, the diamond grains in the polycrystalline diamond matrix 4 has an average grain size (d50 diamond ) of between 0.8-30 µm. For example, d50 diamond is between 0.8-25µm. For example, d50 diamond is between 0.8-20 µm. For example, d50 diamond is between 0.8-15 µm. For example, d50 diamond is between 1-12 µm. This is measured by Electron Backscatter Diffraction (EBSD). Advantageously, this produces a material with a polycrystalline diamond matrix wherein the embedded cemented carbide entities are homogeneously distributed throughout. Furthermore, it controls size and quantity of binder lakes.

[0023] The diamond-grain size could also be determined using EBSD on a cross-section of an ion polished sintered sample.

[0024] Settings and method for EBSD analysis on diamond grain size are: Table 1. Settings for the EBSD analysis in Aztec 6.0.ParametersTypical settingsEx 1. Diamond- MapEx 2. Diamond-MapVoltage20 kV20 kVBinning mode4×44×4Area (µm 2< )30×30150×150Step size0.035 µm0.07 µm

[0025] There is an overlap between diamond and Co (fcc) unit cells and therefore the Co (fcc) was excluded. The diamond phase selected was from the HKL database.

[0026] The post-processing was performed using AztecCrystal 2.2 software. For diamond map, cleaning contained wild spike removal and zero solution removal down to 5 neighbours with 10 iterations per step. Diamond-diamond boundaries were defined as having a misorientation angle larger than 10 degrees and boundaries were closed. Boarder grains were excluded. Smallest grain was defined as having size of 50 pixels in area.

[0027] The grain sizes were taken directly from the AztecCrystal software under grain size tab. Area-weighted statistic for equivalent circle diameter was selected for each analysis and map. "D50" is the equivalent circle diameter Dn where the combined area of the grains smaller than Dn is equal 50% of the total grain area.

[0028] In some example embodiments, the volume % (vol%) of cemented carbide entities 6 is between 2-75. For example, 6-75 vol% cemented carbide entities. For example, 8-73 vol% cemented carbide entities. For example, 8-70 vol% cemented carbide entities. Advantageously, this volume gives a continuous polycrystalline diamond matrix with properties tailored to the application, for increased toughness a higher percentage of cemented carbide entities is desirable and for a higher wear resistance a lower percentage of cemented carbide entities is desirable. The vol% of cemented carbide entities was analysed by processing SEM images in the Image J software. Initially a calibration of the scale (pixels / µm) in the SEM images was made by first measuring the scale bar in the SEM-image using the straight-line measuring function in Image J. The obtained data from this measurement and the dimension of the scale bar in the SEM-image are then processed using the "Set scale" function to finalize the calibration. The SEM image was then converted to an 8 bit image format (unless already in a 8 bit image format). The volume% was regarded to correspond with the area%. Initially the images were filtered using the Gaussian blur function with default settings of Sigma (Radius) 2.00. After this a binary image, with the objective to return the cemented carbide as white and the both the diamond and the binder (Co) as black (background) was then made using the auto-thresholding method "Minimum". Following this, the binary image was cleaned up with the "Open" command. Finally to assess the area% cemented carbide entities the "analyze particles function" was employed with settings for Size of 0-Infinity, Circularity of 0.00-1.00, Show of Overlay Masks, Exclude on edges not selected and Include holes not selected.

[0029] In some example embodiments, the average grain size of the metal carbide in the cemented carbide entities (d50 metalcarbide ) is between 0.3 - 8 µm. For example, between 0.4 - 6 µm. For example, between 0.5 - 5 µm. For example, between 0.6 -5 µm. The average WC grain size is evaluated either using the Jeffries method described below from at least one different micrograph for each material, preferably two or more. If several micrographs are used an average value was then calculated from the mean grain size values obtained from the individual micrographs (for each material respectively). The procedure for the mean grain size evaluation using a modified Jeffries method was the following: A rectangular frame of suitable size was selected within the SEM micrograph so as to contain a minimum of 150 WC grains. The grains inside the frame and those intersected by the frame are manually counted, and the mean grain size is obtained from equations (1-3): M = L scale mm × 10 − 3 L scale micro × 10 − 6 vol % WC = 100 × − 1.308823529 × wt % Co 100 − 1 wt % Co 100 + 1.308823529 d = 1500 M × L 1 × L 2 × vol % WC n 1 + n 2 2 × 100 Where: d = WC grain size (µm) L 1 , L 2 = length of sides of the frame (mm) M = magnificationL scale mm = measured length of scale bar on micrograph in mm L scale micro = actual length of scale bar with respect to magnification (µm) n 1 = no. grains fully within the frame n 2 = no. grains intersected by frame boundary wt%Co = known cobalt content in weight %.

[0030] Equation (2) is used to estimate the WC fraction based on the known Co content in the material. Equation (3) then yields the mean WC grain size from the ratio of the total WC area in the frame to the number of grains contained in it. Equation (3) also contains a correction factor compensating for the fact that in a random 2D section, not all grains will be sectioned through their maximum diameter.

[0031] Optionally, or when the binder is not Co, the WC-grain size could also be determined using EBSD on a cross-section of an ion polished sintered sample. This is more precise, but more time-consuming method also give information regarding grain size distribution. When comparing Jeffries and EBSD grain size the area d50 value from EBSD corresponds well with the Jeffries value. "D50" is the equivalent diameter Dn where the combined area of the grains smaller than Dn is equal 50% of the total grain area.

[0032] Settings and method for EBSD analysis on WC grain size are: Table 2. Settings for the EBSD analysis in Aztec 6.0.ParametersTypical settingsEx 1. WC- MapEx 2. WC- MapVoltage20 kV20 kVBinning mode4×44×4Area (µm 2< )30×3020×20Step size0.02 µm0.07 µm

[0033] The post-processing was performed using AztecCrystal 2.2 software. For WC auto-cleaning was used with an addition of Pseudo-symmetry rotations removal of axis 0001 with and angle of 30 degrees (allowed deviating angle 5 degrees). WC-WC boundaries were defined as having a misorientation angle larger than 3 degrees and boundaries being closed. Boarder grains were excluded. Smallest grain was defined as having size of 4 pixels in area.

[0034] In some example embodiments the binder content in the cemented carbide entities is between 0.5 - 20 wt%, preferably between 2-18 wt%, more preferably 5-15 wt%. Preferably, the binder content in the cemented carbide part of the matrix is >1 wt%, more preferable >2 wt%, more preferable >3 wt%, more preferably >4wt%; most preferably >5 wt%, the binder content is <20 wt%, more preferably <15wt%, most preferable <14 wt%. This is measured by using energy dispersive spectroscopy (EDS) or WDS (wavelength dispersive spectroscopy) on cemented carbide areas of the sintered sample phase.

[0035] In some example embodiments the binder phase of the cemented carbide, is selected from cobalt, nickel, iron or a mixture thereof, more preferably cobalt.

[0036] In some example embodiments the cemented carbide entities further comprise one or more elements selected from Cr, Ta, Ti, Nb, Mo, Zr and V present as elements or as carbides, nitrides or carbonitrides or a mixture thereof in contents from 100 ppm up to 15 wt% depending on the element added and the purpose of the addition. Advantageously, the addition of one or more of these elements is that they act as a grain growth inhibitor will control grain growth in entities. Further it lowers the melting point for HPHT synthesis which is beneficial as it reduces the fatigue on the cemented carbide dies in the press, thereby saving money and material. When the grain growth inhibitor is chromium, it also provides the advantage of increasing the plastic deformation and corrosion resistance of the material.

[0037] In some example embodiments the cemented carbide entities further comprises a gamma phase selected from a carbide or nitride of niobium, tantalum, titanium or a mixture thereof. Advantageously, the presence of the gamma phase increases the wear resistance of cemented carbide matrix. When the gamma phase is tantalum or niobium the plastic deformation resistance at elevated temperatures is increased.

[0038] In some example embodiments the average diameter of the cemented carbide entities 6 (d50 CCentities ) is between 5-60 µm. For example, d50 CCentities is between 5 - 55 µm. For example, d50 CCentities is between 5- 50 µm. The average diameter of the cemented carbide entities 6 was analyzed by processing SEM images in the Image J software. Initially a calibration of the scale (pixels / µm) in the SEM images was made by first measuring the scale bar in the SEM-image using the straight-line measuring function in Image J. The obtained data from this measurement and the dimension of the scale bar in the SEM-image are then processed using the "Set scale" function to finalize the calibration. The SEM image was then converted to an 8 bit image format (unless already in a 8 bit image format). Initially the images were filtered using the Gaussian blur function with default settings of Sigma (Radius) 2.00. After this a binary image, with the objective to return the cemented carbide as white and the both the diamond and the binder (Co) as black (background) was then made using the auto-thresholding method "Minimum". Following this, the binary image was cleaned up with the "Open" command. Finally, to assess the diameter of the cemented carbide entities the" analyse particles function" was employed with settings for Size of 0-Infinity, Circularity of 0.00-1.00, Show of Overlay Masks, Exclude on edges selected and Include holes not selected. The d50 for the "Feret's diameter" (i.e., the longest distance between any two points along the outline) was calculated and used for the average diameter of the cemented carbide entities 6 (d50 CCentities ).

[0039] In some example embodiments d50 CCentities / d50 diamond is > 2. For example, d50 CC entities / d50 diamond is >2.3. For example, d50 CC entities / d50 diamond is >2.5. For example, d50 CC entities / d50 diamond is >2.7. Below this ratio the desired microstructure with spherical shaped cemented carbide entities homogenously distributed and embedded in the continuous polycrystalline diamond matrix is not formed. A continuous polycrystalline diamond matrix is desirable for achieving a high wear resistance and good thermal conductivity which is important in many applications. Homogenously distributed cemented carbide entities will give a more homogenous Co-distribution in the sintered material since the SCCG acts as local catalyst / binder emitters during HPHT and thus defects as large binder pools. If there is insufficient catalyst / binder infiltration during HPHT binder deficient areas where the diamonds convert into graphite due to local non-pressurized areas can be formed. Binder pools or lakes and graphite are defects that lower the performance of the sintered material and should thus be avoided or minimized. Insufficient catalyst / binder infiltration is also a limiting factor for the maximum height of the polycrystalline diamond comprised table that can be produced, especial when using fine grained diamond feed.

[0040] In some example embodiments d50 CCentities / d50 diamond is <20. For example, d50 CCentities / d50 diamond is <17. For example, d50 CCentities / d50 diamond is <15. Above this ratio large clusters of polycrystalline diamond matrix are formed giving an inhomogeneous distribution of the cemented carbide entities that will result in an non uniform performing material.

[0041] In some example embodiments the binder content in the polycrystalline diamond matrix 4 is between 5-35 wt% which corresponds to about 2 - 18 vol% if the binder is Co(W) and if the polycrystalline diamond matrix is essentially free from metal carbide precipitations. This amount of binder makes it possible to optimize the toughness and the thermal stability of the polycrystalline diamond matrix by targeting a high or low metallic binder content. For example, between 6-30 wt%. For example, between 7-25 wt%. The binder content in the cemented carbide entities is less compared to the starting binder content of the SCCG as it has migrated to the polycrystalline diamond matrix.

[0042] In some example embodiments the concentration of binder in the polycrystalline diamond matrix 4 increases from an area surrounding the cemented carbide entities 6 to areas positioned further away from the cemented carbide entities 6. In other words, the binder concentration (for example, the cobalt concentration) in the polycrystalline diamond matrix 4 is lowest in areas surrounding or adjacent to the cemented carbide entities 6 and highest in areas in between or furthest away from the cemented carbide entities 6. The carbon concentration in the polycrystalline diamond matrix 4 is highest in areas surrounding or adjacent to the cemented carbide entities 6 and lowest in areas in between or furthest away from the cemented carbide entities 6. In other words, there is a Co depleted rim around the each of the cemented carbide entities. In other words, there is a carbon rich rim around each of the carbide entities. This is shown in figure 3, which is a SEM image at × 2000 magnification.

[0043] In some example embodiments the cemented carbide entities 6 have a d50 aspect ratio of <1.62. For example, the cemented carbide entities 6 have a d50 aspect ratio of <1.61. For example, the cemented carbide entities 6 have a d50 aspect ratio of <1.60 A d50 aspect ratio close to 1 indicates that the SCCG kept their shape during HPHT and that the pressure distribution during HPHT was homogenous and that the densification was even in all directions, which allows that the final shapes and dimensions can be controlled and steered. A d50 aspect ratio close to 1 also indicates that the SCCG are separated from one another in the material post HPHT. This is measured using SEM images processed in the Image J software. Initially a calibration of the scale (pixels / µm) in the SEM images was made by first measuring the scale bar in the SEM-image using the straight-line measuring function in Image J. The obtained data from this measurement and the dimension of the scale bar in the SEM-image are then processed using the "Set scale" function to finalize the calibration. The SEM image was then converted to an 8 bit image format (unless already in a 8 bit image format). The images were then filtered using the Gaussian blur function with default settings of Sigma (Radius) 2.00. After this a binary image, with the objective to return the cemented carbide as white and the both the diamond and the binder (Co) as black (background) was then made using the auto-thresholding method "Minimum". Following this, the binary image was cleaned up with the "Open" command. Finally, to assess the aspect ratio (i.e. the aspect ratio of the particle's fitted ellipse, i.e. Major Axis / Minor Axis) of the cemented carbide entities the" analyse particles function" was employed with settings for Size of 0-Infinity, Circularity of 0.00-1.00, Show of Overlay Masks, Exclude on edges selected and Include holes not selected. The (d50) aspect ratio of the cemented carbide entities 6 was then calculated. For a perfect spherical particle the aspect ratio is 1. The aspect ratio calculated for the images in in two dimensions is regarded to correspond to the particle in three dimensions.

[0044] In some example embodiments the d99 / d50 for the polycrystalline diamond matrix 4 area segments between the cemented carbide entities 6 is < 30. For example, d99 / d50 for the polycrystalline diamond matrix 4 area segments between the cemented carbide entities 6 is < 25. For example, d99 / d50 for polycrystalline diamond matrix 4 area segments between the cemented carbide entities 6 is < 20. For example, d99 / d50 for the polycrystalline diamond matrix 4 area segments between the cemented carbide entities 6 is < 15. A lower d99 / d50 ratio for the polycrystalline diamond matrix 4 area segments between the cemented carbide entities 6 shows a more homogenous distribution of the cemented carbide entities that are embedded in the polycrystalline diamond matrix.

[0045] Figure 4 shows an insert 10 for a mining or rock cutting or wear part application comprising the material 2 as disclosed hereinbefore or hereinafter. Advantageously, if the material of the present invention is used for inserts for mining, rock cutting or wear parts applications, the lifetime of the inserts will be increased due to the wear resistant nature of the material in combination with the increased toughness. The Inserts typically comprise a base portion 12 (otherwise known as a substrate); a working tip potion 14 and a core 16. It should however be understood that the insert could have a different form. The insert 10 could for example have a symmetrical or asymmetrical formation. In one embodiment, the insert 10 has a domed working tip portion 14 comprising the composite material 2 as described hereinbefore or hereinafter and a base portion 12 comprising cemented carbide.

[0046] In one embodiment the cemented carbide base portion contains 4-15 wt% Co. In one embodiment the cemented carbide base portion contains Cr. In one embodiment the cemented carbide base portion has a room temperature Vickers hardness between 900 - 1650 HV20. In one embodiment the cemented carbide base portion has a fracture toughness K1C >10 mPa / m 1 / 2< measured with Palmqvist method from 30 kg Vickers indents using Shetty's formula.

[0047] Preferably, for a percussive application as top hammer or DTH (Down the hole) drilling the binder concentration is between 4-12 wt%, more preferably between 4-10 wt% most preferable 5-8 wt%. Preferably, the average grain size of the hard metal is between 0.7-5 µm, more preferably between 1-4 µm with a room temperature hardness of 1200-1650 HV20.

[0048] Preferably, for rotary applications the binder concentration is between 8-20 wt%, more preferably between 8-15 wt%, most preferable 10-15 wt%. Preferably, the average metal carbide (WC) grain size of the hard metal is between 2-10 µm, preferably between 2- 8 µm, most preferably between 2-6 µm with a room temperature hardness of between 1000-1300 HV20.

[0049] Preferably, for mechanical rock cutting the binder concentration is between 6-15 wt%, more preferably between 6-12 wt%. Preferably, the average metal carbide (WC) grain size of the hard metal is between 6-18 µm, more preferably between 6-15 µm with a room temperature hardness of 800 - 1100 HV20.

[0050] Preferably, for a wear part applications, for example but not limited to support inserts in drill bits, the binder concentration is between 3-10 wt%, more preferably between 3-8 wt% most preferable 3-7 wt%. Preferably, the average metal carbide (WC) grain size of the hard metal is between 0.6- 4 µm, more preferably between 0.6-3 µm with a room temperature hardness of 1300-2000 HV20.

[0051] Preferably, the diameter of the base portion 12 is between 5-40 mm, more preferably between 7-30 mm, most preferably between 7-24 mm.

[0052] Preferably, the thickness of the tip portion 14 is between 0.1-15 mm, more preferably between 0.2-10 mm, even more preferably between 0.5 - 5 mm, most preferable 0.8 - 4 mm when measured along the longitudinal axis.

[0053] Preferably, the volume of the tip portion 14 is between 2- 50 vol% of the total volume of the insert 10, more preferably 5-40 vol%, most preferably 8-30 vol%.

[0054] Alternatively, the insert 10 may be freestanding without a cemented carbide base.

[0055] Another aspect of the present invention relates to a method for making a material 2 as disclosed hereinbefore or hereinafter comprising the steps of: a) providing diamond grains having an average grain size (d50 diafeed ) between 0.8 - 30 µm; b) providing sintered cemented carbide granules (SCCG) having a diameter (d50 SCCGfeed ) of 5-60 µm and wherein d50 SCCGfeed / d50 diafeed is ≥2; c) blending the diamond grains with the SCCG to form a homogenous blend; d) placing the blend into preformed refractory metal cup; e) providing a refractory metal lid, or, a pre-sintered or sintered cemented carbide base on top of the blend to close the cup; f) pre-compacting the blend in the refractory metal cup; g) surrounding the cup with a pressure media; h) inserting the pressure media surrounded cup into a high pressure high temperature container; i) placing the above container in a high pressure high temperature press and sintering at high pressure and high temperature to form a composite material.

[0056] In some example embodiment the grain size of the diamond feedstock (d50 diafeed ) is between 0.8- 30 µm. For example, d50 diafeed is between 0.8 - 25 µm. For example, d50 diafeed is between 0.8 - 15 µm. For example, d50 diafeed is between 1-12 µm. The diamond grains are typically added in the form of a diamond powder but could alternatively be added as a slurry or in any other suitable form.

[0057] During HPHT the SCCG acts as localized pre-alloyed catalyst / binder (Co)-releasers which gives a well sintered thick continuous polycrystalline diamond comprising table.

[0058] The SCCG is manufactured by preparing a slurry of the powders with the desired composition and WC grain size are mixed with an organic binder, usually PEG, and a liquid, usually a water / ethanol blend. The slurry is then spray dried to form granules.

[0059] The sintering temperature of the cemented carbide granules is used both to control the metal carbide grain size and the density and is preferable between 1250 - 1550 °C, more preferably between 1270- 1500 °C, most preferably between 1300-1500 °C. Depending on the sintering temperature the sintered cemented carbide granules are preferably fully dense or at least 90% dense, depending on the composition and sintering temperature of the granules. The sintering can be performed in vacuum, or in N 2 / Ar atmosphere, or, at least partly, in a carburizing atmosphere which can be provided by one or more carbon containing gases e.g. CO 2 , CO and CH 4 .

[0060] The sintering process are usually started with a de-binding step where the organic binder is removed. The de-binding step is usually performed at a temperature between 300 and 600°C.

[0061] In one embodiment the SCCG are substantially fully dense. Using fully dense or near fully dense cemented carbide granules below a certain D50 or D90 is beneficial to controlling the homogeneity when blending diamond which is a lighter material with SCCG which is a heavier material.

[0062] For step c) the blending could be done by vibrating, turbola blending or shaking for example in a commercial paint shaker.

[0063] For step d) the refractory metal cup is preferably made from titanium but could also be made from niobium, molybdenum, zirconium or tantalum or any other suitable refractory metal. The cup is shaped as required by the product being formed.

[0064] For step e) either a refractory metal lid, or a pre-sintered or a sintered cemented carbide pre-shaped base is inserted on top of the blend inside the refractory metal cup in order to close the cup. The choice of the cemented carbide base in terms of grain size and composition is made depending on the target application. By "pre-sintered" is herein meant that the cemented carbide base has not been sintered to full density prior to being placed in the cup. It will reach full density during the subsequent HPHT step.

[0065] For step f) either a refractory metal or a sintered hard metal pre-shaped substrate is inserted on top of the blend inside the refractory metal cup in order to close the cup. Advantageously if a hard metal substrate is added this enables a cemented carbide base portion to be formed and the shape of the cutting tip to be designed or adjusted to fit the application for example by allowing a higher amount of cemented carbide granule and diamond blend in one part or one side of the tip. The choice of the cemented carbide base portion in terms of grain size and binder content is made depending on the target application.

[0066] For step g) the pressure media could for example is hBN or an NaCl mixture that becomes molten during the high temperature high pressure stage at or above the diamond stable region.

[0067] For step h) the high pressure container for example could be, but not limited to a natural and synthetically reconstituted pyrophyllite cube or cylinder.

[0068] For step i) a typical HPHT cycle comprises a fast ramp for 50-65 seconds to a max pressure of 52 kBar and a temperature of 1225°C and then a smooth transition into a lower ramp of 200-300 seconds at 52 kBar gradually climbing up to a sintering soak temperature. the typical soaking temperature is between 1350-1425°C for 100-200 seconds a sharp transition into a down ramp with maintained pressure of 52 kBar for 200-400 seconds; an instant cut of electrical power and a natural cooling ramp with cooling water jackets dissipating the heat for 40 seconds and a gradual release of the applied pressure. The temperature is controlled by W-Re thermocouples inside the cube. The full cycle is about 15-25 minutes. The sintering temperature used is typically 1300-1500°C, preferably 1320-1450°C, most preferable 1350- 1420°C. The sintering pressure used is typically 50kBar to 60kBar, preferably 50kBar-55kBar, most preferably 52kBar.

[0069] Following HPHT the outer diamater of the part is then cleaned up using centerless grinding and when needed the cup on the dome is removed either using grinding or by blasting with SiC-grits. If the part is a mining insert it is then ground to the exact dimensions required. If required the inserts can then be subjected to shot blasting and / or tumbling, for example high energy tumbling. The inserts can then be shrink fit to be brazed into a cavity in a drill bit.

[0070] In some example embodiments 2-75 vol% SCCG was provided. For example, 6-75 vol% SCCG was provided. For example, 8-73 vol% SCCG was provided. For example, 8-70 vol% SCCG was provided. The total weight of the mixtures in the examples was typically between 0.3 g to 5.4 g. The total weight of the mixture is determined as required by the product being formed.

[0071] In some example embodiments the average diameter of the SCCG (d50 SCCGfeed ) is in the range of 5-60 µm. Advantageously, this range provides good flowability and high powder density and the mass of each SCCG is more equal to the mass of a diamond particle. In some example embodiments, d50 SCCGfeed is between 5-55 µm. In some example embodiments, d50 SCCGfeed is between 5-50 µm. d50 SCCGfeed was measured using laser diffraction fully compliant with ISO 13320 for the complete size range from 0.1 µm to 8750µm from Sympatec GmbH using a Helos BR instrument with Rodos M / Vibri dry sampling unit. The powder is analysed with a combination of R3 (0.9 to 175µm) and R5 (4.5 to 875µm) measuring ranges. For each measuring range the samples are analysed three times using 0.5g of powder. The results from the two measuring ranges were then combined in the Windox 5.7.2.2 software to cover the range 0.9 to 875 µm.

[0072] In one embodiment the D90 size of SCCG is <100 µm, for example <90 µm, for example < 80 µm, for example <60 µm. This can also be measured using laser diffraction fully compliant with ISO 13320 as described above. Advantageously, this provides a smaller distance to the next cemented carbide granule and is also important for the mass of the granule which should be as close to the mass of the diamonds in the feed as possible to reduce the risk of separation during blending and filling of the cup which will be of great importance for the homogeneity of the final material.

[0073] In one embodiment the (d90 - d10) range of cemented carbide granules is < 50 µm, preferably < 40 µm, more preferably < 30 µm. This can also be measured using laser diffraction fully compliant with ISO 13320 as described above. Advantageously, a narrow distribution of the sintered cemented carbide granules provides a more homogenous distribution of the cemented carbide granules within the polycrystalline diamond matrix and the distances between the cemented carbide granules within the composite material will be easier to control and thus the properties of the material will be more even.

[0074] The d10, d50 and d90 are calculated using Windox software. d10, d50, or d90 is defined as the size value corresponding to cumulative size distribution at 10%, 50%, or 90% respectively, which represents the size of particles below which 10%, 50%, or 90% of the sample lies. Alternative notations are x10, x50 and x90, as used in Windox software.

[0075] In some example embodiments, the average metal carbide grain size within the SCCG (d50 metalcarbidefeed ) is between 0.3 - 8 µm. Advantageously, this grain size range provides the means to balance and optimize the hardness and toughness for mining applications. For example, d50 metalcarbidefeed is between 0.5 - 5 µm. For example, d50 metalcarbidefeed is between 0.6 - 5 µm. The grain is measured by image analysis on SEM images either from secondary or back-scatter electron images using Jeffries method giving an average grain size or from analysis of an EBSD-image on an ion polished surface using the area D50 value.

[0076] The binder phase content, in the SCCG feed prior to HPHT is between 0.5-20 wt%, more preferably between 2-18 wt%, most preferably between 5-15 wt%. In some example embodiments the binder is cobalt. The binder phase content in the cemented carbide part of the composite after HPHT can be analysed by EDS (energy dispersive spectroscopy) or more preferable WDS (wavelength dispersive spectroscopy) on a sufficient large ion polished area where only cemented carbide is present.

[0077] In some example embodiment the relative powder density of the SCCG is >35% compared with the density of the fully sintered body of such granules. For example, the relative powder density of the SCCG is >40%. For example, the relative powder density of the SCCG is >45%. The powder density (or apparent density) is measured by using a Hall flow meter and filling a known volume (Hall density cup) using a funnel placed above where the powder is added.

[0078] In some example embodiments the SCCG powder has a tap density is preferable >40%, more preferably >50%, most preferably >55% relative to a full sintered body. The tap density is obtained when filling a known volume (Hall density cup or similar) with the powder granules and tap or "knock" to make them pack even tighter. Advantageously, a high granule density provides that the diamond grains are fixed in their position after filling the refractory metal cup. Moreover, it allows a lower shrinkage during HPHT which is beneficial for the shape and size control and also for avoiding sudden pressure drops during HPHT (so called blow-outs) which can result in catastrophic failures of the cemented carbide dies in the HPHT cell.

[0079] In some example embodiments the SCCG have a K1C fracture toughness >10 MPa / m 1 / 2< measured with Palmqvist method from 30 kg Vickers indents using Shetty's formula.

[0080] In some example embodiments the cemented carbide granules have graphite or other sp 2< -carbon on their surface prior to the HPHT step. Advantageously, this will lower the binder-melting point and ease the infiltration of the diamond grains and will convert into diamond since the HPHT process is carried out at or above the diamond stable region in presence of a catalytic metal, preferably Co.

[0081] Is some example embodiments d50 SCCGfeed / d50 diafeed is > 2. For example, d50 SCCGfeed / d50 diafeed is >2.5. For example, d50 SCCGfeed / d50 diafeed is > 2.7. For example, d50 SCCGfeed / d50 diafeed is >2.8. For example, d50 SCCGfeed / d50 diafeed is >3.0.

[0082] References in the description to "one embodiment," "an embodiment," "an example embodiment," etc., indicate that the embodiment described may include a particular feature or a particular combination of features (e.g., component(s), element(s), integer(s), structure(s), operation(s), and / or step(s)), but every embodiment may not necessarily include the particular feature or the particular combination of features. Such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, or a particular combination of features, is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to implement such feature, or combination of features, in connection with other embodiments whether or not explicitly described.EXAMPLES Summary of samples - powder blends

[0083] Table 3 shows the powder blends used. Cemented carbide base portions (substrates) were manufactured using conventional methods and used for making sample A-P. For sample Q a desired dome geometry aiming for percussive drilling operations of the tip portion was formed on top. The thickness of the sintered diamond-SCCG was around 1 mm for sample A-F and sample I-P. The thickness of the sintered diamond-SCCG was around 5 mm for samples G, H and Q. The composition of the SCCG 1 in grade 1A, 1B and 1C feedstock (i.e., prior to HPHT sintering) was 13 wt% Co, 0.56 wt% Cr and balance WC and with a sintered density of 14.16 g / cm3. The composition of SCCG grade 2 was 12 wt% Co and balance WC and a sintered density of 14.32 g / cm3. The Co-content in the diamond powders was 0 wt% prior to HPHT. The composition of the cemented carbide substrate in samples A-Q was 12 wt% Co, 0.5 wt% TiC, 2.5 wt% (Ta,Nb)C and had a hardness of 90.2 HRA. Table 3: Summary of powder blendsSampleGrade SCCGVol% SCCG *Diamond feed gradeAverage grain size of diamond feedstock (d50 diamondfeed ) (µm)Average size of SCCG (d50 SCCGfeed ) (µm)Ratio d50 SCCGfeed / d50 diafeed A (comparison)1A50SJK-5 0-10.510.721.4B (comparison)1B50SJK-5 0-10.523.547.4C (invention)1B50SJK-5 1-3210.75.35D (comparison)1A85SJK-5 1-3223.511.75E (invention)1A70SJK-5 1-3223.511.75F (invention)1A50SJK-5 1-3223.511.75G (invention)1A25SJK-5 1-223.511.753H (invention)1A10SJK-5 1-3223.511.75I (invention)250SJK-5 1-3223.211.6K (invention)1A50SJK-5 3-5423.55.88L (comparison)1B70SJK-5 5-7610.71.78M (comparison)1B50SJK-5 5-7610.71.78N (invention)1B50SJK 5-7623.53.92O (comparison)1B50SJK-5 6-12910.71.19P (invention)1C50SJK-5 6-12932.43.60Q (invention)1A70SJK-5 1-3223.511.75*Balance is diamond feedstock

[0084] SCCG can be prepared from spray dried granules using conventional means, i.e., preparing a slurry is prepared where powders with the desired composition and WC grain size are mixed with an organic binder, usually PEG and a liquid, usually a water / ethanol blend. The slurry is then spray dried to form granules.

[0085] The sintering process is usually started with a de-binding step where the organic binder is removed. The de-binding step is usually performed at a temperature between 300 and 600°C. The sintering temperature of the cemented carbide granules is used to control both the WC-grain size and the density and is preferably between 1250 - 1550 °C, more preferably between 1270- 1500 °C, most preferably between 1300-1500 °C. Depending on the sintering temperature the sintered cemented carbide granules are preferably fully dense or at least 90% dense, depending on the composition and sintering temperature of the granules. The sintering can be performed in vacuum, or in N 2 / Ar atmosphere, or, at least partly, in a carburizing atmosphere which can be provided by one or more carbon containing gases e.g., CO 2 , CO and CH 4 .

[0086] After sintering the powder density of the SCCG 1A was 8.4 g / cm 3< ; the relative density of the SCCG was 59 %; the tap density of the SCCG was 9.2 g / cm 3< and the relative tap density was 65% After sintering the powder density of the SCCG 1B was 7.6 g / cm 3< ; the relative density of the SCCG was 53 %; the tap density of the SCCG was 8.7 g / cm 3< and the relative tap density was 62% After sintering the powder density of the SCCG 1C was 8.0 g / cm 3< ; the relative density of the SCCG 1C was 56 %; the tap density of the SCCG 1C was 8.5 g / cm3andthe relative tap densiry was 60% . The SCCG 1A,1B and 1C had a hardness of 1380; a toughness of 17.08 MPa / m ½< measured by Palmqvist K1C; and an average metal carbide grain size of 0.75 µm measured using Jeffries. After sintering the powder density of the SCCG 2 was 7.8 g / cm 3< ; the relative density of the SCCG2 was 55 %; the tap density of the SCCG2 was 8.8 g / cm 3< and the relative tap density was 62% The SCCG 2 had a hardness of 1300; a toughness of 18.30 MPa / m ½< ) by Palmqvist K1C and an average metal carbide grain size of 1.2 µm measured using Jeffries.

[0087] The hardness and toughness of the sintered SCCG and cemented carbides can be controlled by their composition.

[0088] The diamond powders were purchased from Hyperion Materials & Technology of metal bond grade SJK-5. The numbers after the "SJK-5" in the diamond feed grade column in table 3 show the grain size range in microns, i.e., "SJK-5 3-5" means that the diamond grain size range is between 3-5 µm.

[0089] The SCCG and the diamond powder was then blended by using a Caulk VARI-MIX II vibrating unit for 2.5 minutes or using a commercially available paint shaker Corob Evo shake 500 at max rpm for 5 minutes. Then the powder blend was poured into a titanium refractory metal cup with a wall thickness of 127µm. This was followed by providing a sintered cemented carbide base on top of the powder blend to close the cup and thus containing the assembly. The powder blend in the refractory metal cup was pre-compacted by pushing the cemented carbide body on the powder blend. The contained assembly was then surrounded by a pressure media being hexagonal Boron Nitride (hBN); a Carbon Foil Heater, and a cylinder made up of a mixture of carbon lampblack and sodium chloride. These internal components where then contained within a reconstituted pyrophyllite pressure media container; the pressure media container was then inserted into a high pressure high temperature (HPHT) cubic press and sintering at high pressure and high temperature to form a domed shaped insert. The HPHT sintering was conducted at 52 kbars pressure. The sintering temperature used was 1350°.

[0090] Following the HPHT sintering the inserts were then ground and / or blasted with SiC to clean the dome.Material properties post HPHT sintering

[0091] Tables 4 show the properties of the material post HPHT sintering. Table 4: Material properties post HPHT sinteringSampleImage investigatedVol% Cemented Carbide entitiesContinuous polycrystalline diamond matrix?PCD area segments between Cemented Carbide entitiesCemented carbide entities characteristicsmag.area (mm 2< )%(Yes or No)d99 / d50d50 SCCGentities diameter (µm)d50 aspect ratioA (comp)200×0.1546Yes40n / an / aB (comp)80×0.4838Yes53n / an / aC (inv)200×0.1633Yes881.42D (comp)200×0.0986Non / an / an / aE (inv)200×0.2063Yes8111.35F (inv)200×0.2038Yes9131.42G (inv)200×0.2618Yes11121.24H (inv)200×0.198Yes8131.26I (inv)200×0.2040Yes9121.41K (inv)200×0.2142Yes9151.58L (comp)200×0.2667Non / an / an / aM (comp)200×0.2036Yes6101.67N (inv)200×0.2343Yes8141.54O (comp)200×0.1939Yes7101.62P (inv)200×0.1741Yes11321.49Q (inv)250×0.1759Yes881.29

[0092] Comparative samples A and B have a high d99 / d50 for the polycrystalline diamond matrix 4 area segments between the cemented carbide entities 6 showing large areas of polycrystalline diamond matrix and a non-homogenous distribution of the cemented carbide entities that are embedded in the polycrystalline diamond matrix. Hence, comparative samples A and B are having a non-homogenous microstructure. Figure 2 is an SEM image at x500 magnification of comparative sample A, showing large areas of polycrystalline diamond matrix and a non-homogenous distribution of the cemented carbide entities that are embedded in the polycrystalline diamond matrix.

[0093] Comparative samples D and L do not have a continuous polycrystalline matrix.

[0094] Comparative samples M and O have high d50 aspect ratio, showing that the cemented carbide entities do not have a spherical geometry.

[0095] The inventive sample all have a continuous polycrystalline diamond matrix and a homogenous distribution of cemented carbide entities having a substantially spherical geometry.

[0096] Table 5 shows the grain sizes of the diamond in the polycrystalline diamond matrix and the metal carbide in the cemented carbide entities. Table 5: Grain size by EBSD of diamond and metal carbide (WC) post HPHT sinteringSampleAverage diamond grain size (d50 diamatrix )(µm)Average grain size of metal carbide in cemented carbide entities (d50 metalcarbide ) (µm)A (comparative)Could not be indexed in EBSD0.71C (inventive)1.120.65H (inventive)1.03n / aN (inventive)3.500.67P (inventive)5.360.64 Benchmark and comparative samples

[0097] Tables 6 and 7 show the properties of commercially available samples that are considered to be the state of the art and the "benchmark" for the properties for the inserts produced according the invention disclosed herein. These samples have high diamond contents and therefore a much more expensive to produce than the inventive samples. These samples are produced with three layers of diamond in the dome, with each layer having a different concentration of diamond. Table 6: Benchmark PCD samples purchased from MegadiamondSampleD50 WC grain size in diamond layer 1 (cutting layer) from EBSDCo (wt%) content from EDS on WC-Co area in diamond layer 1D50 diamond grain size by EBSD (µm)D50 WC grain size in cemented carbide substrate from EBSDComposition of cemented carbide substrate from EDS (wt%)R (benchmark)0.395.48.321.898.8 Co, balance WCS (benchmark)0.458.29.981.648.2 Co, Balance WC Table 7: Diamond properties of the comparative benchmark samples SampleDiamond content in layer 1 (cutting layer) by Image analysis on 500X SEM image (area %)Diamond content in layer 2 (middle) by Image analysis on 500X SEM image (area %)Diamond content in layer 3 (next to substrate) by Image analysis on 500X SEM image (area %)Thickness of diamond layer 1 (µm)Thickness of diamond layer 2 (µm)Thickness of diamond layer 3 (µm)R745036630470430S745533990400360

[0098] Table 8 shows further a comparative sample, containing cemented carbide and no diamond. The samples shown in this table are produced by conventional sintering at a temperature of 1410 °C in vacuum and applying an argon pressure at 60 bars at maximum temperature. Tables 8: Properties of cemented carbide comparative sampleSampleGrain size of the metal carbide (WC) (µm)Nominal composition (wt%)HV20K1C (MPa / m)T (SH70)1.726.0 Co, balance WC145011.2 4< Homogeneity

[0099] SEM images was taken about 1 / 10th of the distance from the surface from the top of the dome / sample (surface) and about 1 / 10th of the distance from the substrate to assess the homogeneity of the cemented carbide entities. The volume% was regarded to correspond with the area%. Tables 9 show assessed SEM images with Image J version 1.54d. Table 9: Homogeneity of inventive materialSampleArea about 1 / 10th of the distance from the substrateArea about 1 / 10th of the distance from the surfaceSEM image analysedArea Cemented Carbide entitiesSEM image analysedArea Cemented Carbide entitiesmag.area (mm 2< )%mag.area (mm 2< )YoG (inventive)500X0.0414500X0.0420Q (inventive)650X0.0363500X0.0459S (benchmark)1000X0.01671000X0.0124

[0100] The results from Table 9 show that the volume of the cemented carbide entities in inventive samples is homogeneous and that the volume of the cemented carbide entities in the benchmark sample is non-homogeneous.

[0101] Figures 1a and 1b are SEM images at x500 and x1000 magnification respectively of inventive sample C having a homogenous microstructure.

[0102] Figure 2 is an SEM image at x500 magnification of comparative sample A having a non-homogenous microstructure.

[0103] The results show that the distribution of the SCCG entities within the polycrystalline diamond matrix are homogenous for the inventive samples.Lathe wear test

[0104] The samples tested in an abrasion wear test, wherein the sample tips are worn against a rotating granite log counter surface in a turning operation. The test parameters used were as follows: 100 N load applied to each insert, granite log rpm ~190, log diameter ranging from 130 to 150 mm, and a horizontal feed rate of 0.339 mm / rev. As much of the length of the log (max 300 mm) was used in each test to remove that difference in composition in the rock have a significant impact on the results. If large piece broke out from the log this area was avoided and therefore the length in some tests were shorter than 300 mm. The sliding distance varied due to the difference in diameter and length of the part of the rock that could be used but were around 330-460 m and the mass loss versus sliding distance was approximately linear between the three samples of each grade that was tested. The sample was cooled by a continuous flow of water. Each sample was carefully cleaned and weighed prior to and after the test. Mass loss of one sample per material was evaluated, the sample volume loss for each of the tested materials was calculated from the measured mass loss and sample density, the results are presented in table 10. Table 10: Wear test resultsSampleDiamond content (vol% or area%)Calculated sintered density (g / cm^3)Mass loss (g)Estimated volume loss / meter (mm^3 / m)Q (invention)3010.970.00023.91 x10 -5< R (benchmark)74 (outer layer 1)0.00000S (benchmark)74 (outer layer 1)6.40.00013.26 x10 -5< T (comparison)014.160.00471.01 x10 -3<

[0105] The result show that the inventive samples have a lower wear rate than the comparative samples and similar wear rate compared to the benchmark examples even though they have been produced with lower diamond content and consequently at lower cost.Insert compression test

[0106] The insert compression test method involves compressing a drill bit insert between two plane-parallel hard counter surfaces, at a constant displacement rate, until the failure of the insert. A test fixture based on the ISO 4506:2017 (E) standard "Hardmetals - Compression test" was used, with cemented carbide anvils grade H6F from Hyperion having a hardness exceeding 2000 HV, while the test method itself was adapted to toughness testing of rock drill inserts. The fixture was fitted onto an Instron 5989 test frame. The loading axis was identical with the axis of rotational symmetry of the inserts. The counter surfaces of the fixture fulfilled the degree of parallelism required in the ISO 4506:2017 (E) standard, i.e. a maximum deviation of 0.5 µm / mm. The tested inserts were loaded at a constant rate of crosshead displacement equal to 0.6 mm / min until failure, while recording the load-displacement curve. The compliance of the test rig and test fixture was subtracted from the measured load-displacement curve before test evaluation. One diamond composite insert was tested but at least three cemented carbide inserts per run. The counter surfaces were inspected for damage before each test. Insert failure was defined to take place when the measured load suddenly dropped by at least 1000 N. Subsequent inspection of tested inserts confirmed that this in all cases this coincided with the occurrence of a macroscopically visible crack. The load at fracture was measured and the material strength was calculated and is characterized by means of the total absorbed deformation energy until fracture and calculated from the maximum load at fracture and the displacement of the insert. The summary inserts crushing strength (IC) and fracture energy (Ec), in Joules (J), required to crush the samples is shown in table 11 below: Table 11: Insert compression test resultsSampleIC (kN)Fracture energy Ec (J)Q (invention)747.1T (comparison)353.0

[0107] Both samples tested were "as-sintered" 10 mm spherical dome inserts. The crushing tests show that the strength of the inventive insert was significantly improved compared to the cemented carbide reference inserts.EDS results

[0108] Table 12 shows the chemical composition of the material post HPHT sintering. Prior to HPHT sintering the Co-content in the SCCG-1 granules was 13 wt% and the Co-content in the diamond powders was 0 wt%. Table 12: EDS resultsSampl eVol% diamon dsCoconte nt in the SCCG-entitie s (wt%)Co-content in the polycrystalli ne diamond matrix (wt%)Cr-content in the polycrystalli ne diamond matrix (wt%)W-content in the polycrystalli ne diamond matrix (wt%)Ti-content in the polycrystalli ne diamond matrix (wt%)C-content in the polycrystalli ne diamond matrix (wt%)E (inv)307.7230.280.583.130.2465.77F (inv)503.6222.410.362.170.1574.91G (inv)752.1222.15-2.51-75.34H (inv)902.8615.23-2.87-81.90

Examples

examples

EXAMPLES

Summary of samples - powder blends

[0083]Table 3 shows the powder blends used. Cemented carbide base portions (substrates) were manufactured using conventional methods and used for making sample A-P. For sample Q a desired dome geometry aiming for percussive drilling operations of the tip portion was formed on top. The thickness of the sintered diamond-SCCG was around 1 mm for sample A-F and sample I-P. The thickness of the sintered diamond-SCCG was around 5 mm for samples G, H and Q. The composition of the SCCG 1 in grade 1A, 1B and 1C feedstock (i.e., prior to HPHT sintering) was 13 wt% Co, 0.56 wt% Cr and balance WC and with a sintered density of 14.16 g / cm3. The composition of SCCG grade 2 was 12 wt% Co and balance WC and a sintered density of 14.32 g / cm3. The Co-content in the diamond powders was 0 wt% prior to HPHT. The composition of the cemented carbide substrate in samples A-Q was 12 wt% Co, 0.5 wt% TiC, 2.5 wt% (Ta,Nb)C and had a hardness of 90.2 HRA.

Table 3: Summa...

Field of invention

[0001] The present invention relates to a composite material comprising cemented carbide entities in a polycrystalline diamond matrix for use in mining or rock cutting applications or wear parts and a method for producing the same.Background art

[0002] PCD (poly crystalline diamond) is well known for being highly wear resistant, making it a popular choice for making industrial applications. However, for toughness demanding mining applications, such as inserts for percussive and rotary drilling (with the exception of oil and gas) or mechanical cutting, PCD works less well due to its brittle behaviour, which limits the lifespan of the inserts. Cemented carbide has a unique combination of high elastic modulus, high hardness, high compressive strength, high wear and abrasion resistance together with a good level of toughness. Therefore, cemented carbide is commonly used in products such as mining and cutting inserts. Cemented carbide comprises a hard ceramic (carbide) phase and a binder phase.

[0003] It is desirable to combine the high wear resistance of the PCD with the toughness of the cemented carbide. However, known composite materials comprising diamond and cemented carbide are not so well balanced regarding the wear resistance to toughness relation making them prone to breaking and unreliable when for example used for mining inserts.

[0004] The best performing prior art PCD-inserts used for percussive drilling have layers with different diamond concentrations in the domed region of the insert, however the problem with this is that it demands a rather complex manufacture procedure which makes the material very expensive. The problem to be solved is how to provide a new material that is able to provide high performance, having the optimal balance between hardness, toughness and thermal conductivity, without excessive manufacturing costs, where the properties of the material can be tailored to suit the application.

[0005] A further problem to be solved relates to limitations of diamond layer thickness. A binder, which is typically cobalt, is infiltrated into the diamond layer for structural stability either from the cemented carbide substrate or by adding fine-grained binder powder. When a cemented carbide substrate is used the infiltration into the diamond table is limited to around 2 mm and this therefore limits the thickness of the diamond layer that it is possible to produce. The addition of fine-grained binder powders is problematic as it is difficult to homogenously blend and is easily oxidised. Therefore, an additional problem to be solved is how to produce thicker diamond-based layers.DEFINITIONS

[0006] By "cemented carbide" is herein meant a material that comprises at least 50 wt% tungsten carbide, possibly other hard constituents common in the art of making cemented carbides and a metallic binder phase preferably selected from one or more of Fe, Co and Ni.

[0007] By "HPHT" is herein meant a "High Pressure High Temperature" process with pressures about at or above the diamond stable region (>50 kBar) and with temperatures of at least about 1000 C.

[0008] By "SCCG" is herein meant a sintered cemented carbide cluster with at least 10 tungsten carbide grains and a metallic binder preferable based on Co and / or Ni and Fe. Preferably, the SCCG are spherical.

[0009] By "cemented carbide entity" is herein meant a sintered cemented carbide granule which is embedded in the polycrystalline diamond matrix with d50 between 5 - 60 µm having a substantially spherical shape, containing at least 10 tungsten carbide grains and a metallic binder preferable based on Co and / or Ni and Fe.

[0010] By "homogenously distributed throughout" is herein meant that the cemented carbide entities are evenly distributed throughout the composite material and that no distinguishable pattern in the distribution of the cemented carbide entities can be seen.

[0011] Examples of distinguishable patterns could be a gradient in either size, volume or number of the cemented carbide entities or that the material contains satellite structures wherein there would be a plurality of the smaller entities surrounding a larger entity.Summary of the Invention

[0012] According to the first aspect of the present invention, there is a composite material comprising a continuous polycrystalline diamond matrix embedded with cemented carbide entities which are homogeneously distributed throughout; wherein the polycrystalline diamond matrix comprises diamond and binder; and wherein the cemented carbide entities comprise metal carbide and binder.

[0013] Advantageously, this provides a material having an optimal balance between hardness, toughness and thermal conductivity, therefore providing a material that is more reliable and less prone to chipping and breaking. Furthermore, the properties of both the cemented carbide entities and the surrounding polycrystalline diamond matrix can be tailored to suit the application the material is being used for. As the cemented carbide entities act as localized catalyst / binder emitter it is also possible to produce thicker diamond-based layers having a high diamond content.

[0014] A further aspect of the present invention relates to a method for making a material as described hereinbefore or hereinafter comprising the steps of: a) providing diamond having an average grain size (d50 diafeed ) between 0.8-30 µm; b) providing sintered cemented carbide granules (SCCG) having a diameter (d50 SCCGfeed ) of 5-60 µm and wherein d50 SCCGfeed / d50 diafeed is ≥2. c) blending the diamond with the SCCG to form a homogenous blend; d) placing the blend into preformed refractory metal cup; e) providing a refractory metal lid; or a pre-sintered or sintered cemented carbide base on top of the blend to close the cup; f) pre-compacting the blend in the refractory metal cup; g) surrounding the cup with a pressure media; h) inserting the pressure media surrounded cup into a high-pressure high temperature container; i) placing the above container in a high-pressure high temperature press and sintering at high pressure and high temperature to form a composite material.

[0015] Advantageously, this results a material having a polycrystalline diamond matrix with cemented carbide entities homogeneously embedded therein. Furthermore, this method provides a more homogenous blend which provides uniform properties throughout the volume of the material, higher powder density, reduced and more controllable shrinkage during HPHT sintering cycle which means that there is greater control over the final shape of the product being produced. Further, it means that the properties of material can be steered as required for a specific application.Brief description of drawings

[0016] A specific implementation of the present invention will now be described, by way of example only, and with reference to the accompanying drawings in which: Figures 1a and 1b are SEM images at x500 and x1000 magnification respectively that show the structure of the inventive sample C material. Figure 2 is an SEM image at x500 magnification of comparative sample A Figure 3 is an SEM image taken at x2000 magnification. Figure 4 is a schematic drawing of a mining insert. Detailed description

[0017] Figures 1a and 1b are SEM images at x500 and x1000 magnification respectively showing the composite material 2. The composite material 2 comprises a continuous polycrystalline diamond matrix 4 embedded with cemented carbide entities 6 which are homogeneously distributed throughout. The polycrystalline diamond matrix 4 comprises diamond and binder; and wherein the cemented carbide entities comprise metal carbide and binder.

[0018] Figures 1a and 1b clearly show the homogeneous distribution of the cemented carbide entities 6 in the polycrystalline diamond matrix 4.

[0019] In one embodiment the distribution of the cemented carbide entities 6 in the polycrystalline diamond matrix 4 is a normal distribution. In other words, there is a single modal distribution of the cemented carbide entities 6. In another embodiment, there may be a multi modal distribution of the cemented carbide entities 6.

[0020] The cemented carbide entities 6 are homogenously distributed throughout the polycrystalline diamond matrix 4 in three dimensions in terms of: the distance between the neighbouring cemented carbide entities 6 throughout the material; the volume of the polycrystalline diamond matrix 4 between the cemented carbide entities 6; the volume of the cemented carbide entities 6 throughout the material is homogenously distributed, meaning that the cemented carbide entities 6 are evenly distributed throughout the composite material 2 and that no distinguishable pattern in the distribution of the cemented carbide entities 6 can be seen. Examples of distinguishable patterns could be a gradient in either size, volume or number of the cemented carbide entities or that the material contains satellite structures wherein there would be a plurality of smaller entities surrounding a larger entity. This could be investigated by analysing SEM or LOM images with Image J of the ground, lapped and ion polished material. The ion polishing was conducted for at least 190 minutes at 6 V and for at least 20 minutes at 2V with a sample angle of 4 degrees and continuous rotation. Initially a calibration of the scale (pixels / µm) in the SEM images was made by first measuring the scale bar in the SEM-image using the straight-line measuring function in Image J. The obtained data from this measurement and the dimension of the scale bar in the SEM-image are then processed using the "Set scale" function to finalize the calibration. The SEM image was then converted to an 8 bit image format (unless already in a 8 bit image format). The homogeneity in of terms of the volume of the polycrystalline diamond matrix 4 between the cemented carbide entities 6, was investigated by assessing the size distribution of the polycrystalline diamond matrix 4 area segments between the cemented carbide entities 6. The area segments obtained is regarded to correspond to the volume segments. The scaled image in the 8 bit format of the material were filtered using the Gaussian blur function with default settings of Sigma (Radius) 2.00.

[0021] After this a binary image, with the objective to return both the diamond and the binder (Co) as white and the cemented carbide as black (background) was made using the auto-thresholding method "Minimum". Following this, the binary image was cleaned up with the "Open" command. As a next step, the Watershed command was used. Finally, to assess polycrystalline diamond matrix 4 area segments between the cemented carbide entities, the" analyse particles function" was employed with settings for Size of 0-Infinity, Circularity of 0.00-1.00, Show of Overlay Masks, Exclude on edges selected and Include holes not selected. The d99 and the d50 were calculated for the mentioned area segments, as well as, the d99 / d50 ratio. A lower d99 / d50 for the polycrystalline diamond matrix 4 area segments between the cemented carbide entities 6 shows a more homogenous distribution of the cemented carbide entities that are embedded in the polycrystalline diamond matrix. The homogeneity in of terms of that the volume of the cemented carbide entities 6 throughout the material is homogenously distributed, could be investigated by comparing SEM or LOM from an area near in the bulk of the material and an area near the surface. The area% of the cemented carbide phase obtained is regarded to correspond to the volume% of the cemented carbide phase. The difference between the volume of the cemented carbide granules in the area near the surface and the volume of cemented carbide entities in the area in the bulk of the material (i.e. ((highest value- lowest value) / Highest value)* 100) is less than 15%, preferably less than 10%. By an "area near the surface" is defined as about 1 / 10th of the distance from the surface (i.e. the cutting edge) and by an "area in the bulk of the material" is defined as being about 1 / 10th of the distance from the substrate if there is a substrate present or about 1 / 10th of the distance from the bottom of the insert if there is no substrate present.

[0022] In some example embodiments, the diamond grains in the polycrystalline diamond matrix 4 has an average grain size (d50 diamond ) of between 0.8-30 µm. For example, d50 diamond is between 0.8-25µm. For example, d50 diamond is between 0.8-20 µm. For example, d50 diamond is between 0.8-15 µm. For example, d50 diamond is between 1-12 µm. This is measured by Electron Backscatter Diffraction (EBSD). Advantageously, this produces a material with a polycrystalline diamond matrix wherein the embedded cemented carbide entities are homogeneously distributed throughout. Furthermore, it controls size and quantity of binder lakes.

[0023] The diamond-grain size could also be determined using EBSD on a cross-section of an ion polished sintered sample.

[0024] Settings and method for EBSD analysis on diamond grain size are: Table 1. Settings for the EBSD analysis in Aztec 6.0.ParametersTypical settingsEx 1. Diamond- MapEx 2. Diamond-MapVoltage20 kV20 kVBinning mode4×44×4Area (µm 2< )30×30150×150Step size0.035 µm0.07 µm

[0025] There is an overlap between diamond and Co (fcc) unit cells and therefore the Co (fcc) was excluded. The diamond phase selected was from the HKL database.

[0026] The post-processing was performed using AztecCrystal 2.2 software. For diamond map, cleaning contained wild spike removal and zero solution removal down to 5 neighbours with 10 iterations per step. Diamond-diamond boundaries were defined as having a misorientation angle larger than 10 degrees and boundaries were closed. Boarder grains were excluded. Smallest grain was defined as having size of 50 pixels in area.

[0027] The grain sizes were taken directly from the AztecCrystal software under grain size tab. Area-weighted statistic for equivalent circle diameter was selected for each analysis and map. "D50" is the equivalent circle diameter Dn where the combined area of the grains smaller than Dn is equal 50% of the total grain area.

[0028] In some example embodiments, the volume % (vol%) of cemented carbide entities 6 is between 2-75. For example, 6-75 vol% cemented carbide entities. For example, 8-73 vol% cemented carbide entities. For example, 8-70 vol% cemented carbide entities. Advantageously, this volume gives a continuous polycrystalline diamond matrix with properties tailored to the application, for increased toughness a higher percentage of cemented carbide entities is desirable and for a higher wear resistance a lower percentage of cemented carbide entities is desirable. The vol% of cemented carbide entities was analysed by processing SEM images in the Image J software. Initially a calibration of the scale (pixels / µm) in the SEM images was made by first measuring the scale bar in the SEM-image using the straight-line measuring function in Image J. The obtained data from this measurement and the dimension of the scale bar in the SEM-image are then processed using the "Set scale" function to finalize the calibration. The SEM image was then converted to an 8 bit image format (unless already in a 8 bit image format). The volume% was regarded to correspond with the area%. Initially the images were filtered using the Gaussian blur function with default settings of Sigma (Radius) 2.00. After this a binary image, with the objective to return the cemented carbide as white and the both the diamond and the binder (Co) as black (background) was then made using the auto-thresholding method "Minimum". Following this, the binary image was cleaned up with the "Open" command. Finally to assess the area% cemented carbide entities the "analyze particles function" was employed with settings for Size of 0-Infinity, Circularity of 0.00-1.00, Show of Overlay Masks, Exclude on edges not selected and Include holes not selected.

[0029] In some example embodiments, the average grain size of the metal carbide in the cemented carbide entities (d50 metalcarbide ) is between 0.3 - 8 µm. For example, between 0.4 - 6 µm. For example, between 0.5 - 5 µm. For example, between 0.6 -5 µm. The average WC grain size is evaluated either using the Jeffries method described below from at least one different micrograph for each material, preferably two or more. If several micrographs are used an average value was then calculated from the mean grain size values obtained from the individual micrographs (for each material respectively). The procedure for the mean grain size evaluation using a modified Jeffries method was the following: A rectangular frame of suitable size was selected within the SEM micrograph so as to contain a minimum of 150 WC grains. The grains inside the frame and those intersected by the frame are manually counted, and the mean grain size is obtained from equations (1-3): M = L scale mm × 10 − 3 L scale micro × 10 − 6 vol % WC = 100 × − 1.308823529 × wt % Co 100 − 1 wt % Co 100 + 1.308823529 d = 1500 M × L 1 × L 2 × vol % WC n 1 + n 2 2 × 100 Where: d = WC grain size (µm) L 1 , L 2 = length of sides of the frame (mm) M = magnificationL scale mm = measured length of scale bar on micrograph in mm L scale micro = actual length of scale bar with respect to magnification (µm) n 1 = no. grains fully within the frame n 2 = no. grains intersected by frame boundary wt%Co = known cobalt content in weight %.

[0030] Equation (2) is used to estimate the WC fraction based on the known Co content in the material. Equation (3) then yields the mean WC grain size from the ratio of the total WC area in the frame to the number of grains contained in it. Equation (3) also contains a correction factor compensating for the fact that in a random 2D section, not all grains will be sectioned through their maximum diameter.

[0031] Optionally, or when the binder is not Co, the WC-grain size could also be determined using EBSD on a cross-section of an ion polished sintered sample. This is more precise, but more time-consuming method also give information regarding grain size distribution. When comparing Jeffries and EBSD grain size the area d50 value from EBSD corresponds well with the Jeffries value. "D50" is the equivalent diameter Dn where the combined area of the grains smaller than Dn is equal 50% of the total grain area.

[0032] Settings and method for EBSD analysis on WC grain size are: Table 2. Settings for the EBSD analysis in Aztec 6.0.ParametersTypical settingsEx 1. WC- MapEx 2. WC- MapVoltage20 kV20 kVBinning mode4×44×4Area (µm 2< )30×3020×20Step size0.02 µm0.07 µm

[0033] The post-processing was performed using AztecCrystal 2.2 software. For WC auto-cleaning was used with an addition of Pseudo-symmetry rotations removal of axis 0001 with and angle of 30 degrees (allowed deviating angle 5 degrees). WC-WC boundaries were defined as having a misorientation angle larger than 3 degrees and boundaries being closed. Boarder grains were excluded. Smallest grain was defined as having size of 4 pixels in area.

[0034] In some example embodiments the binder content in the cemented carbide entities is between 0.5 - 20 wt%, preferably between 2-18 wt%, more preferably 5-15 wt%. Preferably, the binder content in the cemented carbide part of the matrix is >1 wt%, more preferable >2 wt%, more preferable >3 wt%, more preferably >4wt%; most preferably >5 wt%, the binder content is <20 wt%, more preferably <15wt%, most preferable <14 wt%. This is measured by using energy dispersive spectroscopy (EDS) or WDS (wavelength dispersive spectroscopy) on cemented carbide areas of the sintered sample phase.

[0035] In some example embodiments the binder phase of the cemented carbide, is selected from cobalt, nickel, iron or a mixture thereof, more preferably cobalt.

[0036] In some example embodiments the cemented carbide entities further comprise one or more elements selected from Cr, Ta, Ti, Nb, Mo, Zr and V present as elements or as carbides, nitrides or carbonitrides or a mixture thereof in contents from 100 ppm up to 15 wt% depending on the element added and the purpose of the addition. Advantageously, the addition of one or more of these elements is that they act as a grain growth inhibitor will control grain growth in entities. Further it lowers the melting point for HPHT synthesis which is beneficial as it reduces the fatigue on the cemented carbide dies in the press, thereby saving money and material. When the grain growth inhibitor is chromium, it also provides the advantage of increasing the plastic deformation and corrosion resistance of the material.

[0037] In some example embodiments the cemented carbide entities further comprises a gamma phase selected from a carbide or nitride of niobium, tantalum, titanium or a mixture thereof. Advantageously, the presence of the gamma phase increases the wear resistance of cemented carbide matrix. When the gamma phase is tantalum or niobium the plastic deformation resistance at elevated temperatures is increased.

[0038] In some example embodiments the average diameter of the cemented carbide entities 6 (d50 CCentities ) is between 5-60 µm. For example, d50 CCentities is between 5 - 55 µm. For example, d50 CCentities is between 5- 50 µm. The average diameter of the cemented carbide entities 6 was analyzed by processing SEM images in the Image J software. Initially a calibration of the scale (pixels / µm) in the SEM images was made by first measuring the scale bar in the SEM-image using the straight-line measuring function in Image J. The obtained data from this measurement and the dimension of the scale bar in the SEM-image are then processed using the "Set scale" function to finalize the calibration. The SEM image was then converted to an 8 bit image format (unless already in a 8 bit image format). Initially the images were filtered using the Gaussian blur function with default settings of Sigma (Radius) 2.00. After this a binary image, with the objective to return the cemented carbide as white and the both the diamond and the binder (Co) as black (background) was then made using the auto-thresholding method "Minimum". Following this, the binary image was cleaned up with the "Open" command. Finally, to assess the diameter of the cemented carbide entities the" analyse particles function" was employed with settings for Size of 0-Infinity, Circularity of 0.00-1.00, Show of Overlay Masks, Exclude on edges selected and Include holes not selected. The d50 for the "Feret's diameter" (i.e., the longest distance between any two points along the outline) was calculated and used for the average diameter of the cemented carbide entities 6 (d50 CCentities ).

[0039] In some example embodiments d50 CCentities / d50 diamond is > 2. For example, d50 CC entities / d50 diamond is >2.3. For example, d50 CC entities / d50 diamond is >2.5. For example, d50 CC entities / d50 diamond is >2.7. Below this ratio the desired microstructure with spherical shaped cemented carbide entities homogenously distributed and embedded in the continuous polycrystalline diamond matrix is not formed. A continuous polycrystalline diamond matrix is desirable for achieving a high wear resistance and good thermal conductivity which is important in many applications. Homogenously distributed cemented carbide entities will give a more homogenous Co-distribution in the sintered material since the SCCG acts as local catalyst / binder emitters during HPHT and thus defects as large binder pools. If there is insufficient catalyst / binder infiltration during HPHT binder deficient areas where the diamonds convert into graphite due to local non-pressurized areas can be formed. Binder pools or lakes and graphite are defects that lower the performance of the sintered material and should thus be avoided or minimized. Insufficient catalyst / binder infiltration is also a limiting factor for the maximum height of the polycrystalline diamond comprised table that can be produced, especial when using fine grained diamond feed.

[0040] In some example embodiments d50 CCentities / d50 diamond is <20. For example, d50 CCentities / d50 diamond is <17. For example, d50 CCentities / d50 diamond is <15. Above this ratio large clusters of polycrystalline diamond matrix are formed giving an inhomogeneous distribution of the cemented carbide entities that will result in an non uniform performing material.

[0041] In some example embodiments the binder content in the polycrystalline diamond matrix 4 is between 5-35 wt% which corresponds to about 2 - 18 vol% if the binder is Co(W) and if the polycrystalline diamond matrix is essentially free from metal carbide precipitations. This amount of binder makes it possible to optimize the toughness and the thermal stability of the polycrystalline diamond matrix by targeting a high or low metallic binder content. For example, between 6-30 wt%. For example, between 7-25 wt%. The binder content in the cemented carbide entities is less compared to the starting binder content of the SCCG as it has migrated to the polycrystalline diamond matrix.

[0042] In some example embodiments the concentration of binder in the polycrystalline diamond matrix 4 increases from an area surrounding the cemented carbide entities 6 to areas positioned further away from the cemented carbide entities 6. In other words, the binder concentration (for example, the cobalt concentration) in the polycrystalline diamond matrix 4 is lowest in areas surrounding or adjacent to the cemented carbide entities 6 and highest in areas in between or furthest away from the cemented carbide entities 6. The carbon concentration in the polycrystalline diamond matrix 4 is highest in areas surrounding or adjacent to the cemented carbide entities 6 and lowest in areas in between or furthest away from the cemented carbide entities 6. In other words, there is a Co depleted rim around the each of the cemented carbide entities. In other words, there is a carbon rich rim around each of the carbide entities. This is shown in figure 3, which is a SEM image at × 2000 magnification.

[0043] In some example embodiments the cemented carbide entities 6 have a d50 aspect ratio of <1.62. For example, the cemented carbide entities 6 have a d50 aspect ratio of <1.61. For example, the cemented carbide entities 6 have a d50 aspect ratio of <1.60 A d50 aspect ratio close to 1 indicates that the SCCG kept their shape during HPHT and that the pressure distribution during HPHT was homogenous and that the densification was even in all directions, which allows that the final shapes and dimensions can be controlled and steered. A d50 aspect ratio close to 1 also indicates that the SCCG are separated from one another in the material post HPHT. This is measured using SEM images processed in the Image J software. Initially a calibration of the scale (pixels / µm) in the SEM images was made by first measuring the scale bar in the SEM-image using the straight-line measuring function in Image J. The obtained data from this measurement and the dimension of the scale bar in the SEM-image are then processed using the "Set scale" function to finalize the calibration. The SEM image was then converted to an 8 bit image format (unless already in a 8 bit image format). The images were then filtered using the Gaussian blur function with default settings of Sigma (Radius) 2.00. After this a binary image, with the objective to return the cemented carbide as white and the both the diamond and the binder (Co) as black (background) was then made using the auto-thresholding method "Minimum". Following this, the binary image was cleaned up with the "Open" command. Finally, to assess the aspect ratio (i.e. the aspect ratio of the particle's fitted ellipse, i.e. Major Axis / Minor Axis) of the cemented carbide entities the" analyse particles function" was employed with settings for Size of 0-Infinity, Circularity of 0.00-1.00, Show of Overlay Masks, Exclude on edges selected and Include holes not selected. The (d50) aspect ratio of the cemented carbide entities 6 was then calculated. For a perfect spherical particle the aspect ratio is 1. The aspect ratio calculated for the images in in two dimensions is regarded to correspond to the particle in three dimensions.

[0044] In some example embodiments the d99 / d50 for the polycrystalline diamond matrix 4 area segments between the cemented carbide entities 6 is < 30. For example, d99 / d50 for the polycrystalline diamond matrix 4 area segments between the cemented carbide entities 6 is < 25. For example, d99 / d50 for polycrystalline diamond matrix 4 area segments between the cemented carbide entities 6 is < 20. For example, d99 / d50 for the polycrystalline diamond matrix 4 area segments between the cemented carbide entities 6 is < 15. A lower d99 / d50 ratio for the polycrystalline diamond matrix 4 area segments between the cemented carbide entities 6 shows a more homogenous distribution of the cemented carbide entities that are embedded in the polycrystalline diamond matrix.

[0045] Figure 4 shows an insert 10 for a mining or rock cutting or wear part application comprising the material 2 as disclosed hereinbefore or hereinafter. Advantageously, if the material of the present invention is used for inserts for mining, rock cutting or wear parts applications, the lifetime of the inserts will be increased due to the wear resistant nature of the material in combination with the increased toughness. The Inserts typically comprise a base portion 12 (otherwise known as a substrate); a working tip potion 14 and a core 16. It should however be understood that the insert could have a different form. The insert 10 could for example have a symmetrical or asymmetrical formation. In one embodiment, the insert 10 has a domed working tip portion 14 comprising the composite material 2 as described hereinbefore or hereinafter and a base portion 12 comprising cemented carbide.

[0046] In one embodiment the cemented carbide base portion contains 4-15 wt% Co. In one embodiment the cemented carbide base portion contains Cr. In one embodiment the cemented carbide base portion has a room temperature Vickers hardness between 900 - 1650 HV20. In one embodiment the cemented carbide base portion has a fracture toughness K1C >10 mPa / m 1 / 2< measured with Palmqvist method from 30 kg Vickers indents using Shetty's formula.

[0047] Preferably, for a percussive application as top hammer or DTH (Down the hole) drilling the binder concentration is between 4-12 wt%, more preferably between 4-10 wt% most preferable 5-8 wt%. Preferably, the average grain size of the hard metal is between 0.7-5 µm, more preferably between 1-4 µm with a room temperature hardness of 1200-1650 HV20.

[0048] Preferably, for rotary applications the binder concentration is between 8-20 wt%, more preferably between 8-15 wt%, most preferable 10-15 wt%. Preferably, the average metal carbide (WC) grain size of the hard metal is between 2-10 µm, preferably between 2- 8 µm, most preferably between 2-6 µm with a room temperature hardness of between 1000-1300 HV20.

[0049] Preferably, for mechanical rock cutting the binder concentration is between 6-15 wt%, more preferably between 6-12 wt%. Preferably, the average metal carbide (WC) grain size of the hard metal is between 6-18 µm, more preferably between 6-15 µm with a room temperature hardness of 800 - 1100 HV20.

[0050] Preferably, for a wear part applications, for example but not limited to support inserts in drill bits, the binder concentration is between 3-10 wt%, more preferably between 3-8 wt% most preferable 3-7 wt%. Preferably, the average metal carbide (WC) grain size of the hard metal is between 0.6- 4 µm, more preferably between 0.6-3 µm with a room temperature hardness of 1300-2000 HV20.

[0051] Preferably, the diameter of the base portion 12 is between 5-40 mm, more preferably between 7-30 mm, most preferably between 7-24 mm.

[0052] Preferably, the thickness of the tip portion 14 is between 0.1-15 mm, more preferably between 0.2-10 mm, even more preferably between 0.5 - 5 mm, most preferable 0.8 - 4 mm when measured along the longitudinal axis.

[0053] Preferably, the volume of the tip portion 14 is between 2- 50 vol% of the total volume of the insert 10, more preferably 5-40 vol%, most preferably 8-30 vol%.

[0054] Alternatively, the insert 10 may be freestanding without a cemented carbide base.

[0055] Another aspect of the present invention relates to a method for making a material 2 as disclosed hereinbefore or hereinafter comprising the steps of: a) providing diamond grains having an average grain size (d50 diafeed ) between 0.8 - 30 µm; b) providing sintered cemented carbide granules (SCCG) having a diameter (d50 SCCGfeed ) of 5-60 µm and wherein d50 SCCGfeed / d50 diafeed is ≥2; c) blending the diamond grains with the SCCG to form a homogenous blend; d) placing the blend into preformed refractory metal cup; e) providing a refractory metal lid, or, a pre-sintered or sintered cemented carbide base on top of the blend to close the cup; f) pre-compacting the blend in the refractory metal cup; g) surrounding the cup with a pressure media; h) inserting the pressure media surrounded cup into a high pressure high temperature container; i) placing the above container in a high pressure high temperature press and sintering at high pressure and high temperature to form a composite material.

[0056] In some example embodiment the grain size of the diamond feedstock (d50 diafeed ) is between 0.8- 30 µm. For example, d50 diafeed is between 0.8 - 25 µm. For example, d50 diafeed is between 0.8 - 15 µm. For example, d50 diafeed is between 1-12 µm. The diamond grains are typically added in the form of a diamond powder but could alternatively be added as a slurry or in any other suitable form.

[0057] During HPHT the SCCG acts as localized pre-alloyed catalyst / binder (Co)-releasers which gives a well sintered thick continuous polycrystalline diamond comprising table.

[0058] The SCCG is manufactured by preparing a slurry of the powders with the desired composition and WC grain size are mixed with an organic binder, usually PEG, and a liquid, usually a water / ethanol blend. The slurry is then spray dried to form granules.

[0059] The sintering temperature of the cemented carbide granules is used both to control the metal carbide grain size and the density and is preferable between 1250 - 1550 °C, more preferably between 1270- 1500 °C, most preferably between 1300-1500 °C. Depending on the sintering temperature the sintered cemented carbide granules are preferably fully dense or at least 90% dense, depending on the composition and sintering temperature of the granules. The sintering can be performed in vacuum, or in N 2 / Ar atmosphere, or, at least partly, in a carburizing atmosphere which can be provided by one or more carbon containing gases e.g. CO 2 , CO and CH 4 .

[0060] The sintering process are usually started with a de-binding step where the organic binder is removed. The de-binding step is usually performed at a temperature between 300 and 600°C.

[0061] In one embodiment the SCCG are substantially fully dense. Using fully dense or near fully dense cemented carbide granules below a certain D50 or D90 is beneficial to controlling the homogeneity when blending diamond which is a lighter material with SCCG which is a heavier material.

[0062] For step c) the blending could be done by vibrating, turbola blending or shaking for example in a commercial paint shaker.

[0063] For step d) the refractory metal cup is preferably made from titanium but could also be made from niobium, molybdenum, zirconium or tantalum or any other suitable refractory metal. The cup is shaped as required by the product being formed.

[0064] For step e) either a refractory metal lid, or a pre-sintered or a sintered cemented carbide pre-shaped base is inserted on top of the blend inside the refractory metal cup in order to close the cup. The choice of the cemented carbide base in terms of grain size and composition is made depending on the target application. By "pre-sintered" is herein meant that the cemented carbide base has not been sintered to full density prior to being placed in the cup. It will reach full density during the subsequent HPHT step.

[0065] For step f) either a refractory metal or a sintered hard metal pre-shaped substrate is inserted on top of the blend inside the refractory metal cup in order to close the cup. Advantageously if a hard metal substrate is added this enables a cemented carbide base portion to be formed and the shape of the cutting tip to be designed or adjusted to fit the application for example by allowing a higher amount of cemented carbide granule and diamond blend in one part or one side of the tip. The choice of the cemented carbide base portion in terms of grain size and binder content is made depending on the target application.

[0066] For step g) the pressure media could for example is hBN or an NaCl mixture that becomes molten during the high temperature high pressure stage at or above the diamond stable region.

[0067] For step h) the high pressure container for example could be, but not limited to a natural and synthetically reconstituted pyrophyllite cube or cylinder.

[0068] For step i) a typical HPHT cycle comprises a fast ramp for 50-65 seconds to a max pressure of 52 kBar and a temperature of 1225°C and then a smooth transition into a lower ramp of 200-300 seconds at 52 kBar gradually climbing up to a sintering soak temperature. the typical soaking temperature is between 1350-1425°C for 100-200 seconds a sharp transition into a down ramp with maintained pressure of 52 kBar for 200-400 seconds; an instant cut of electrical power and a natural cooling ramp with cooling water jackets dissipating the heat for 40 seconds and a gradual release of the applied pressure. The temperature is controlled by W-Re thermocouples inside the cube. The full cycle is about 15-25 minutes. The sintering temperature used is typically 1300-1500°C, preferably 1320-1450°C, most preferable 1350- 1420°C. The sintering pressure used is typically 50kBar to 60kBar, preferably 50kBar-55kBar, most preferably 52kBar.

[0069] Following HPHT the outer diamater of the part is then cleaned up using centerless grinding and when needed the cup on the dome is removed either using grinding or by blasting with SiC-grits. If the part is a mining insert it is then ground to the exact dimensions required. If required the inserts can then be subjected to shot blasting and / or tumbling, for example high energy tumbling. The inserts can then be shrink fit to be brazed into a cavity in a drill bit.

[0070] In some example embodiments 2-75 vol% SCCG was provided. For example, 6-75 vol% SCCG was provided. For example, 8-73 vol% SCCG was provided. For example, 8-70 vol% SCCG was provided. The total weight of the mixtures in the examples was typically between 0.3 g to 5.4 g. The total weight of the mixture is determined as required by the product being formed.

[0071] In some example embodiments the average diameter of the SCCG (d50 SCCGfeed ) is in the range of 5-60 µm. Advantageously, this range provides good flowability and high powder density and the mass of each SCCG is more equal to the mass of a diamond particle. In some example embodiments, d50 SCCGfeed is between 5-55 µm. In some example embodiments, d50 SCCGfeed is between 5-50 µm. d50 SCCGfeed was measured using laser diffraction fully compliant with ISO 13320 for the complete size range from 0.1 µm to 8750µm from Sympatec GmbH using a Helos BR instrument with Rodos M / Vibri dry sampling unit. The powder is analysed with a combination of R3 (0.9 to 175µm) and R5 (4.5 to 875µm) measuring ranges. For each measuring range the samples are analysed three times using 0.5g of powder. The results from the two measuring ranges were then combined in the Windox 5.7.2.2 software to cover the range 0.9 to 875 µm.

[0072] In one embodiment the D90 size of SCCG is <100 µm, for example <90 µm, for example < 80 µm, for example <60 µm. This can also be measured using laser diffraction fully compliant with ISO 13320 as described above. Advantageously, this provides a smaller distance to the next cemented carbide granule and is also important for the mass of the granule which should be as close to the mass of the diamonds in the feed as possible to reduce the risk of separation during blending and filling of the cup which will be of great importance for the homogeneity of the final material.

[0073] In one embodiment the (d90 - d10) range of cemented carbide granules is < 50 µm, preferably < 40 µm, more preferably < 30 µm. This can also be measured using laser diffraction fully compliant with ISO 13320 as described above. Advantageously, a narrow distribution of the sintered cemented carbide granules provides a more homogenous distribution of the cemented carbide granules within the polycrystalline diamond matrix and the distances between the cemented carbide granules within the composite material will be easier to control and thus the properties of the material will be more even.

[0074] The d10, d50 and d90 are calculated using Windox software. d10, d50, or d90 is defined as the size value corresponding to cumulative size distribution at 10%, 50%, or 90% respectively, which represents the size of particles below which 10%, 50%, or 90% of the sample lies. Alternative notations are x10, x50 and x90, as used in Windox software.

[0075] In some example embodiments, the average metal carbide grain size within the SCCG (d50 metalcarbidefeed ) is between 0.3 - 8 µm. Advantageously, this grain size range provides the means to balance and optimize the hardness and toughness for mining applications. For example, d50 metalcarbidefeed is between 0.5 - 5 µm. For example, d50 metalcarbidefeed is between 0.6 - 5 µm. The grain is measured by image analysis on SEM images either from secondary or back-scatter electron images using Jeffries method giving an average grain size or from analysis of an EBSD-image on an ion polished surface using the area D50 value.

[0076] The binder phase content, in the SCCG feed prior to HPHT is between 0.5-20 wt%, more preferably between 2-18 wt%, most preferably between 5-15 wt%. In some example embodiments the binder is cobalt. The binder phase content in the cemented carbide part of the composite after HPHT can be analysed by EDS (energy dispersive spectroscopy) or more preferable WDS (wavelength dispersive spectroscopy) on a sufficient large ion polished area where only cemented carbide is present.

[0077] In some example embodiment the relative powder density of the SCCG is >35% compared with the density of the fully sintered body of such granules. For example, the relative powder density of the SCCG is >40%. For example, the relative powder density of the SCCG is >45%. The powder density (or apparent density) is measured by using a Hall flow meter and filling a known volume (Hall density cup) using a funnel placed above where the powder is added.

[0078] In some example embodiments the SCCG powder has a tap density is preferable >40%, more preferably >50%, most preferably >55% relative to a full sintered body. The tap density is obtained when filling a known volume (Hall density cup or similar) with the powder granules and tap or "knock" to make them pack even tighter. Advantageously, a high granule density provides that the diamond grains are fixed in their position after filling the refractory metal cup. Moreover, it allows a lower shrinkage during HPHT which is beneficial for the shape and size control and also for avoiding sudden pressure drops during HPHT (so called blow-outs) which can result in catastrophic failures of the cemented carbide dies in the HPHT cell.

[0079] In some example embodiments the SCCG have a K1C fracture toughness >10 MPa / m 1 / 2< measured with Palmqvist method from 30 kg Vickers indents using Shetty's formula.

[0080] In some example embodiments the cemented carbide granules have graphite or other sp 2< -carbon on their surface prior to the HPHT step. Advantageously, this will lower the binder-melting point and ease the infiltration of the diamond grains and will convert into diamond since the HPHT process is carried out at or above the diamond stable region in presence of a catalytic metal, preferably Co.

[0081] Is some example embodiments d50 SCCGfeed / d50 diafeed is > 2. For example, d50 SCCGfeed / d50 diafeed is >2.5. For example, d50 SCCGfeed / d50 diafeed is > 2.7. For example, d50 SCCGfeed / d50 diafeed is >2.8. For example, d50 SCCGfeed / d50 diafeed is >3.0.

[0082] References in the description to "one embodiment," "an embodiment," "an example embodiment," etc., indicate that the embodiment described may include a particular feature or a particular combination of features (e.g., component(s), element(s), integer(s), structure(s), operation(s), and / or step(s)), but every embodiment may not necessarily include the particular feature or the particular combination of features. Such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, or a particular combination of features, is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to implement such feature, or combination of features, in connection with other embodiments whether or not explicitly described.EXAMPLES Summary of samples - powder blends

[0083] Table 3 shows the powder blends used. Cemented carbide base portions (substrates) were manufactured using conventional methods and used for making sample A-P. For sample Q a desired dome geometry aiming for percussive drilling operations of the tip portion was formed on top. The thickness of the sintered diamond-SCCG was around 1 mm for sample A-F and sample I-P. The thickness of the sintered diamond-SCCG was around 5 mm for samples G, H and Q. The composition of the SCCG 1 in grade 1A, 1B and 1C feedstock (i.e., prior to HPHT sintering) was 13 wt% Co, 0.56 wt% Cr and balance WC and with a sintered density of 14.16 g / cm3. The composition of SCCG grade 2 was 12 wt% Co and balance WC and a sintered density of 14.32 g / cm3. The Co-content in the diamond powders was 0 wt% prior to HPHT. The composition of the cemented carbide substrate in samples A-Q was 12 wt% Co, 0.5 wt% TiC, 2.5 wt% (Ta,Nb)C and had a hardness of 90.2 HRA. Table 3: Summary of powder blendsSampleGrade SCCGVol% SCCG *Diamond feed gradeAverage grain size of diamond feedstock (d50 diamondfeed ) (µm)Average size of SCCG (d50 SCCGfeed ) (µm)Ratio d50 SCCGfeed / d50 diafeed A (comparison)1A50SJK-5 0-10.510.721.4B (comparison)1B50SJK-5 0-10.523.547.4C (invention)1B50SJK-5 1-3210.75.35D (comparison)1A85SJK-5 1-3223.511.75E (invention)1A70SJK-5 1-3223.511.75F (invention)1A50SJK-5 1-3223.511.75G (invention)1A25SJK-5 1-223.511.753H (invention)1A10SJK-5 1-3223.511.75I (invention)250SJK-5 1-3223.211.6K (invention)1A50SJK-5 3-5423.55.88L (comparison)1B70SJK-5 5-7610.71.78M (comparison)1B50SJK-5 5-7610.71.78N (invention)1B50SJK 5-7623.53.92O (comparison)1B50SJK-5 6-12910.71.19P (invention)1C50SJK-5 6-12932.43.60Q (invention)1A70SJK-5 1-3223.511.75*Balance is diamond feedstock

[0084] SCCG can be prepared from spray dried granules using conventional means, i.e., preparing a slurry is prepared where powders with the desired composition and WC grain size are mixed with an organic binder, usually PEG and a liquid, usually a water / ethanol blend. The slurry is then spray dried to form granules.

[0085] The sintering process is usually started with a de-binding step where the organic binder is removed. The de-binding step is usually performed at a temperature between 300 and 600°C. The sintering temperature of the cemented carbide granules is used to control both the WC-grain size and the density and is preferably between 1250 - 1550 °C, more preferably between 1270- 1500 °C, most preferably between 1300-1500 °C. Depending on the sintering temperature the sintered cemented carbide granules are preferably fully dense or at least 90% dense, depending on the composition and sintering temperature of the granules. The sintering can be performed in vacuum, or in N 2 / Ar atmosphere, or, at least partly, in a carburizing atmosphere which can be provided by one or more carbon containing gases e.g., CO 2 , CO and CH 4 .

[0086] After sintering the powder density of the SCCG 1A was 8.4 g / cm 3< ; the relative density of the SCCG was 59 %; the tap density of the SCCG was 9.2 g / cm 3< and the relative tap density was 65% After sintering the powder density of the SCCG 1B was 7.6 g / cm 3< ; the relative density of the SCCG was 53 %; the tap density of the SCCG was 8.7 g / cm 3< and the relative tap density was 62% After sintering the powder density of the SCCG 1C was 8.0 g / cm 3< ; the relative density of the SCCG 1C was 56 %; the tap density of the SCCG 1C was 8.5 g / cm3andthe relative tap densiry was 60% . The SCCG 1A,1B and 1C had a hardness of 1380; a toughness of 17.08 MPa / m ½< measured by Palmqvist K1C; and an average metal carbide grain size of 0.75 µm measured using Jeffries. After sintering the powder density of the SCCG 2 was 7.8 g / cm 3< ; the relative density of the SCCG2 was 55 %; the tap density of the SCCG2 was 8.8 g / cm 3< and the relative tap density was 62% The SCCG 2 had a hardness of 1300; a toughness of 18.30 MPa / m ½< ) by Palmqvist K1C and an average metal carbide grain size of 1.2 µm measured using Jeffries.

[0087] The hardness and toughness of the sintered SCCG and cemented carbides can be controlled by their composition.

[0088] The diamond powders were purchased from Hyperion Materials & Technology of metal bond grade SJK-5. The numbers after the "SJK-5" in the diamond feed grade column in table 3 show the grain size range in microns, i.e., "SJK-5 3-5" means that the diamond grain size range is between 3-5 µm.

[0089] The SCCG and the diamond powder was then blended by using a Caulk VARI-MIX II vibrating unit for 2.5 minutes or using a commercially available paint shaker Corob Evo shake 500 at max rpm for 5 minutes. Then the powder blend was poured into a titanium refractory metal cup with a wall thickness of 127µm. This was followed by providing a sintered cemented carbide base on top of the powder blend to close the cup and thus containing the assembly. The powder blend in the refractory metal cup was pre-compacted by pushing the cemented carbide body on the powder blend. The contained assembly was then surrounded by a pressure media being hexagonal Boron Nitride (hBN); a Carbon Foil Heater, and a cylinder made up of a mixture of carbon lampblack and sodium chloride. These internal components where then contained within a reconstituted pyrophyllite pressure media container; the pressure media container was then inserted into a high pressure high temperature (HPHT) cubic press and sintering at high pressure and high temperature to form a domed shaped insert. The HPHT sintering was conducted at 52 kbars pressure. The sintering temperature used was 1350°.

[0090] Following the HPHT sintering the inserts were then ground and / or blasted with SiC to clean the dome.Material properties post HPHT sintering

[0091] Tables 4 show the properties of the material post HPHT sintering. Table 4: Material properties post HPHT sinteringSampleImage investigatedVol% Cemented Carbide entitiesContinuous polycrystalline diamond matrix?PCD area segments between Cemented Carbide entitiesCemented carbide entities characteristicsmag.area (mm 2< )%(Yes or No)d99 / d50d50 SCCGentities diameter (µm)d50 aspect ratioA (comp)200×0.1546Yes40n / an / aB (comp)80×0.4838Yes53n / an / aC (inv)200×0.1633Yes881.42D (comp)200×0.0986Non / an / an / aE (inv)200×0.2063Yes8111.35F (inv)200×0.2038Yes9131.42G (inv)200×0.2618Yes11121.24H (inv)200×0.198Yes8131.26I (inv)200×0.2040Yes9121.41K (inv)200×0.2142Yes9151.58L (comp)200×0.2667Non / an / an / aM (comp)200×0.2036Yes6101.67N (inv)200×0.2343Yes8141.54O (comp)200×0.1939Yes7101.62P (inv)200×0.1741Yes11321.49Q (inv)250×0.1759Yes881.29

[0092] Comparative samples A and B have a high d99 / d50 for the polycrystalline diamond matrix 4 area segments between the cemented carbide entities 6 showing large areas of polycrystalline diamond matrix and a non-homogenous distribution of the cemented carbide entities that are embedded in the polycrystalline diamond matrix. Hence, comparative samples A and B are having a non-homogenous microstructure. Figure 2 is an SEM image at x500 magnification of comparative sample A, showing large areas of polycrystalline diamond matrix and a non-homogenous distribution of the cemented carbide entities that are embedded in the polycrystalline diamond matrix.

[0093] Comparative samples D and L do not have a continuous polycrystalline matrix.

[0094] Comparative samples M and O have high d50 aspect ratio, showing that the cemented carbide entities do not have a spherical geometry.

[0095] The inventive sample all have a continuous polycrystalline diamond matrix and a homogenous distribution of cemented carbide entities having a substantially spherical geometry.

[0096] Table 5 shows the grain sizes of the diamond in the polycrystalline diamond matrix and the metal carbide in the cemented carbide entities. Table 5: Grain size by EBSD of diamond and metal carbide (WC) post HPHT sinteringSampleAverage diamond grain size (d50 diamatrix )(µm)Average grain size of metal carbide in cemented carbide entities (d50 metalcarbide ) (µm)A (comparative)Could not be indexed in EBSD0.71C (inventive)1.120.65H (inventive)1.03n / aN (inventive)3.500.67P (inventive)5.360.64 Benchmark and comparative samples

[0097] Tables 6 and 7 show the properties of commercially available samples that are considered to be the state of the art and the "benchmark" for the properties for the inserts produced according the invention disclosed herein. These samples have high diamond contents and therefore a much more expensive to produce than the inventive samples. These samples are produced with three layers of diamond in the dome, with each layer having a different concentration of diamond. Table 6: Benchmark PCD samples purchased from MegadiamondSampleD50 WC grain size in diamond layer 1 (cutting layer) from EBSDCo (wt%) content from EDS on WC-Co area in diamond layer 1D50 diamond grain size by EBSD (µm)D50 WC grain size in cemented carbide substrate from EBSDComposition of cemented carbide substrate from EDS (wt%)R (benchmark)0.395.48.321.898.8 Co, balance WCS (benchmark)0.458.29.981.648.2 Co, Balance WC Table 7: Diamond properties of the comparative benchmark samples SampleDiamond content in layer 1 (cutting layer) by Image analysis on 500X SEM image (area %)Diamond content in layer 2 (middle) by Image analysis on 500X SEM image (area %)Diamond content in layer 3 (next to substrate) by Image analysis on 500X SEM image (area %)Thickness of diamond layer 1 (µm)Thickness of diamond layer 2 (µm)Thickness of diamond layer 3 (µm)R745036630470430S745533990400360

[0098] Table 8 shows further a comparative sample, containing cemented carbide and no diamond. The samples shown in this table are produced by conventional sintering at a temperature of 1410 °C in vacuum and applying an argon pressure at 60 bars at maximum temperature. Tables 8: Properties of cemented carbide comparative sampleSampleGrain size of the metal carbide (WC) (µm)Nominal composition (wt%)HV20K1C (MPa / m)T (SH70)1.726.0 Co, balance WC145011.2 4< Homogeneity

[0099] SEM images was taken about 1 / 10th of the distance from the surface from the top of the dome / sample (surface) and about 1 / 10th of the distance from the substrate to assess the homogeneity of the cemented carbide entities. The volume% was regarded to correspond with the area%. Tables 9 show assessed SEM images with Image J version 1.54d. Table 9: Homogeneity of inventive materialSampleArea about 1 / 10th of the distance from the substrateArea about 1 / 10th of the distance from the surfaceSEM image analysedArea Cemented Carbide entitiesSEM image analysedArea Cemented Carbide entitiesmag.area (mm 2< )%mag.area (mm 2< )YoG (inventive)500X0.0414500X0.0420Q (inventive)650X0.0363500X0.0459S (benchmark)1000X0.01671000X0.0124

[0100] The results from Table 9 show that the volume of the cemented carbide entities in inventive samples is homogeneous and that the volume of the cemented carbide entities in the benchmark sample is non-homogeneous.

[0101] Figures 1a and 1b are SEM images at x500 and x1000 magnification respectively of inventive sample C having a homogenous microstructure.

[0102] Figure 2 is an SEM image at x500 magnification of comparative sample A having a non-homogenous microstructure.

[0103] The results show that the distribution of the SCCG entities within the polycrystalline diamond matrix are homogenous for the inventive samples.Lathe wear test

[0104] The samples tested in an abrasion wear test, wherein the sample tips are worn against a rotating granite log counter surface in a turning operation. The test parameters used were as follows: 100 N load applied to each insert, granite log rpm ~190, log diameter ranging from 130 to 150 mm, and a horizontal feed rate of 0.339 mm / rev. As much of the length of the log (max 300 mm) was used in each test to remove that difference in composition in the rock have a significant impact on the results. If large piece broke out from the log this area was avoided and therefore the length in some tests were shorter than 300 mm. The sliding distance varied due to the difference in diameter and length of the part of the rock that could be used but were around 330-460 m and the mass loss versus sliding distance was approximately linear between the three samples of each grade that was tested. The sample was cooled by a continuous flow of water. Each sample was carefully cleaned and weighed prior to and after the test. Mass loss of one sample per material was evaluated, the sample volume loss for each of the tested materials was calculated from the measured mass loss and sample density, the results are presented in table 10. Table 10: Wear test resultsSampleDiamond content (vol% or area%)Calculated sintered density (g / cm^3)Mass loss (g)Estimated volume loss / meter (mm^3 / m)Q (invention)3010.970.00023.91 x10 -5< R (benchmark)74 (outer layer 1)0.00000S (benchmark)74 (outer layer 1)6.40.00013.26 x10 -5< T (comparison)014.160.00471.01 x10 -3<

[0105] The result show that the inventive samples have a lower wear rate than the comparative samples and similar wear rate compared to the benchmark examples even though they have been produced with lower diamond content and consequently at lower cost.Insert compression test

[0106] The insert compression test method involves compressing a drill bit insert between two plane-parallel hard counter surfaces, at a constant displacement rate, until the failure of the insert. A test fixture based on the ISO 4506:2017 (E) standard "Hardmetals - Compression test" was used, with cemented carbide anvils grade H6F from Hyperion having a hardness exceeding 2000 HV, while the test method itself was adapted to toughness testing of rock drill inserts. The fixture was fitted onto an Instron 5989 test frame. The loading axis was identical with the axis of rotational symmetry of the inserts. The counter surfaces of the fixture fulfilled the degree of parallelism required in the ISO 4506:2017 (E) standard, i.e. a maximum deviation of 0.5 µm / mm. The tested inserts were loaded at a constant rate of crosshead displacement equal to 0.6 mm / min until failure, while recording the load-displacement curve. The compliance of the test rig and test fixture was subtracted from the measured load-displacement curve before test evaluation. One diamond composite insert was tested but at least three cemented carbide inserts per run. The counter surfaces were inspected for damage before each test. Insert failure was defined to take place when the measured load suddenly dropped by at least 1000 N. Subsequent inspection of tested inserts confirmed that this in all cases this coincided with the occurrence of a macroscopically visible crack. The load at fracture was measured and the material strength was calculated and is characterized by means of the total absorbed deformation energy until fracture and calculated from the maximum load at fracture and the displacement of the insert. The summary inserts crushing strength (IC) and fracture energy (Ec), in Joules (J), required to crush the samples is shown in table 11 below: Table 11: Insert compression test resultsSampleIC (kN)Fracture energy Ec (J)Q (invention)747.1T (comparison)353.0

[0107] Both samples tested were "as-sintered" 10 mm spherical dome inserts. The crushing tests show that the strength of the inventive insert was significantly improved compared to the cemented carbide reference inserts.EDS results

[0108] Table 12 shows the chemical composition of the material post HPHT sintering. Prior to HPHT sintering the Co-content in the SCCG-1 granules was 13 wt% and the Co-content in the diamond powders was 0 wt%. Table 12: EDS resultsSampl eVol% diamon dsCoconte nt in the SCCG-entitie s (wt%)Co-content in the polycrystalli ne diamond matrix (wt%)Cr-content in the polycrystalli ne diamond matrix (wt%)W-content in the polycrystalli ne diamond matrix (wt%)Ti-content in the polycrystalli ne diamond matrix (wt%)C-content in the polycrystalli ne diamond matrix (wt%)E (inv)307.7230.280.583.130.2465.77F (inv)503.6222.410.362.170.1574.91G (inv)752.1222.15-2.51-75.34H (inv)902.8615.23-2.87-81.90

Examples

examples

EXAMPLES

Summary of samples - powder blends

[0083]Table 3 shows the powder blends used. Cemented carbide base portions (substrates) were manufactured using conventional methods and used for making sample A-P. For sample Q a desired dome geometry aiming for percussive drilling operations of the tip portion was formed on top. The thickness of the sintered diamond-SCCG was around 1 mm for sample A-F and sample I-P. The thickness of the sintered diamond-SCCG was around 5 mm for samples G, H and Q. The composition of the SCCG 1 in grade 1A, 1B and 1C feedstock (i.e., prior to HPHT sintering) was 13 wt% Co, 0.56 wt% Cr and balance WC and with a sintered density of 14.16 g / cm3. The composition of SCCG grade 2 was 12 wt% Co and balance WC and a sintered density of 14.32 g / cm3. The Co-content in the diamond powders was 0 wt% prior to HPHT. The composition of the cemented carbide substrate in samples A-Q was 12 wt% Co, 0.5 wt% TiC, 2.5 wt% (Ta,Nb)C and had a hardness of 90.2 HRA.

Table 3: Summa...

Claims

1. A composite material (2) comprising a continuous polycrystalline diamond matrix (4) embedded with cemented carbide entities (6) which are homogeneously distributed throughout; wherein the polycrystalline diamond matrix (4) comprises diamond and binder; and wherein the cemented carbide entities (6) comprise metal carbide and binder.

2. The composite material (2) according to claim 1 wherein the diamond grains in the polycrystalline diamond matrix (4) have an average grain size (d50diamond) of between 0.8-30 µm.

3. The composite material (2) according to any of the previous claims wherein volume % (vol%) of cemented carbide entities (6) is between 2-75.

4. The composite material (2) according to any of the previous claims wherein the average grain size of the metal carbide (d50metalcarbide) in the cemented carbide entities is between 0.3 - 8 µm.

5. The composite material (2) according to any of the previous claims wherein the average diameter of the cemented carbide entities (6) (d50CCentities) is between 5-60 µm.

6. The composite material (2) according to any of the previous claims wherein d50CCentities / d50daimond is >2.

7. The composite material (2) according to any of the previous claims wherein d50CCentities / d50daimond is <20.

8. The composite material (2) according to any of previous claims wherein binder content in the polycrystalline matrix (4) is between 5-35 wt%.

9. The composite material (2) according to any of the previous claims wherein the concentration of binder in the polycrystalline diamond matrix (4) increases from an area surrounding the cemented carbide entities (6) to areas positioned further away from the cemented carbide entities (6).

10. The composite material (2) according to any of the previous claims wherein the cemented carbide entities (6) have an d50 aspect ratio of <1.62.

11. An insert (10) for a mining or rock cutting or wear part application comprising the material (2) according to any of claims 1-10.

12. A method for making a material (2) according to any of claim 1-10 comprising the steps of: a) providing diamond grains having an average grain size (d50diafeed) between 0.8 - 30 µm; b) providing sintered cemented carbide granules (SCCG) having a diameter (d50SCCGfeed) of 5-60 µm and wherein d50SCCGfeed / d50diafeed is ≥2; c) blending the diamond grains with the SCCG to form a homogenous blend; d) placing the blend into preformed refractory metal cup; e) providing a refractory metal lid, or, a pre-sintered or sintered cemented carbide base on top of the blend to close the cup; f) pre-compacting the blend in the refractory metal cup; g) surrounding the cup with a pressure media; h) inserting the pressure media surrounded cup into a high pressure high temperature container; i) placing the above container in a high pressure high temperature press and sintering at high pressure and high temperature to form a composite material.

13. The method according to claim 12 wherein the average metal carbide grain size (d50metalcarbidefeed) within the SCCG is between 0.3 - 8 µm.

14. The method according to any of claims 12-13 wherein the relative powder density of the SCCG is >35% compared with the density of the fully sintered body of such granules.

15. The method according to any of claims 12 - 14 wherein between 2-75 vol% SCCG was provided

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