Cemented carbide mining insert with alternative binder

Abstract

A sintered cemented carbide insert for rock mining or rock cutting applications comprising a tungsten carbide hard phase, a binder phase and any unavoidable impurities; wherein the binder phase content of the cemented carbide is between 4-18 wt%;wherein the average tungsten carbide grain size is between 0.8 – 15 µm measured using EBSD; wherein binder phase comprises between 48-52 wt% iron, 23-27 wt% nickel as a proportion of the total binder phase; and a balance of cobalt.

Description

[0001] Cemented carbide mining insert with alternative binder

[0002] Field of invention

[0003] The present disclosure generally relates to cemented carbide for rock mining or rock cutting inserts having an alternative binder composition.

[0004] Background art

[0005] Cemented carbide has a unique combination of high elastic modulus, high hardness, high compressive strength, high wear and abrasion resistance with a good level of fracture toughness. Therefore, cemented carbide is commonly used in products such as inserts for rock mining and rock cutting. In general, the hardness and fracture toughness of cemented carbide can be altered by changing the binder content and grain size of the hard phase. Typically, a higher binder content will increase the fracture toughness of the cemented carbide but will decrease its hardness and wear resistance. A finer hard phase grain size will result in cemented carbide with a higher hardness which is more wear resistant, whereas a coarser hard phase grain size will not be as hard but will have higher impact resistance.

[0006] Cobalt is the most commonly used binder for cemented carbide for rock mining and rock cutting applications. There are however concerns about the environmental and health impacts of using cobalt, for example cobalt has been classified as carcinogenic after long term exposure. Therefore, the problem to be solved is how to provide a cemented carbide for rock mining and rock cutting inserts having a binder phase comprising significantly less cobalt that is more sustainable, has less environmental and health concerns but that still performs at least as well as inserts having a cobalt binder.

[0007] There have been problems with previously tested cemented carbides using alternative binders with the control of the tungsten carbide (WC) grain size. For example, nickel-rich binders result in rapid WC grain growth during sintering which leads to in a reduction in the wear resistance; and iron-rich binders, if sintered at the same temperature as cemented carbide having cobalt binder, will produce a material having a reduced WC grain size and consequently increased brittleness leading to increased fracture during drilling.

[0008] US2010 / 0239855 discloses a metal cutting tool comprising an iron-based binder.

[0009] Definitions

[0010] By “cemented carbide” is herein meant a material that comprises at least 50 wt% WC, possibly other hard constituents common in the art of making cemented carbides and a metallic binder phase.

[0011] The term "bulk" is herein meant the cemented carbide of the innermost part (centre) of the rock drill insert.

[0012] The term “green” refers to a cemented carbide mining insert produced by milling the hard phase component(s) and the binder together and then pressing the milled powder to form a compact cemented carbide mining insert, which has not yet been sintered.

[0013] Summary of the Invention

[0014] It is an objective of the present invention to provide a sintered cemented carbide insert for rock mining or cutting applications comprising a tungsten carbide hard phase, a binder phase and any unavoidable impurities; wherein the binder phase content of the cemented carbide is between 4-18 wt%; wherein the average tungsten carbide grain size is between 0.8 - 15 pm measured using EBSD; wherein the binder phase comprises between 48-52 wt% iron, 23-27 wt% nickel as a proportion of the total binder phase; and a balance of cobalt.

[0015] Advantageously, this provides a sintered cemented carbide inserts having a reduced cobalt content, therefore leading to benefits in sustainability, reduced impact to the environment and diminished health concerns. Furthermore, these inserts also offer improved wear resistance and fracture toughness which will increase the lifetime of the inserts. Another aspect of the present application relates to a method of producing a cemented carbide insert as disclosed hereinbefore or hereinafter, comprising the steps of: a) providing a powder mixture comprising between 4-18 wt% binder, any unavoidable impurities and a balance of WC; b) compacting the powder mixture to form a green cemented carbide insert; c) sintering the green carbide mining insert to form a sintered cemented carbide insert; d) subjecting the sintered cemented carbide insert to a tumbling treatment; wherein the binder comprises 48-52 wt% iron, 23-27 wt% nickel as a proportion of the total binder content and a balance of cobalt.

[0016] Advantageously, this provides a method for producing sintered cemented carbide inserts having a reduced cobalt content, therefore providing the benefits previously discussed.

[0017] Brief description of drawings

[0018] 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:

[0019] Figure 1 shows a schematic drawing of a rock drill insert.

[0020] Figure 2 is an XRD plot for inventive sample C.

[0021] Detailed description

[0022] Figure 1 shows a sintered cemented carbide insert 2 (also known as a button) for rock mining or rock cutting applications. The insert 2 comprises a base 4, a working tip 6 and bit central axis 8. The total volume of the insert 2 could be symmetrical or asymmetrical in volume about the insert central axis 8 and have any geometry suitable for rock mining or rock drilling. The sintered cemented carbide insert 2 comprises a tungsten carbide hard phase, a binder phase and any unavoidable impurities. The binder phase content of the cemented carbide is between 4-18 wt%, for example between 4.5 - 16 wt%, for example between 5 - 14 wt%. The average tungsten carbide grain size is between 0.8 - 15 pm, for example between 1 - 12 pm, for example between 1 - 10 pm, for example between 1.2 - 6 pm, for example between 1.4 - 5.0 pm. The average tungsten carbide grain size is measured using EBSD. The binder phase comprises between 48-52 wt% iron, 23-27 wt% nickel as a proportion of the total binder phase; and a balance of cobalt.

[0023] In some example embodiments, the binder phase comprises between 49-51 wt% iron, 24 - 26 wt% nickel and a balance of cobalt. For example, the binder phase comprises 50 wt% iron, 25 wt% nickel and 25 wt% cobalt.

[0024] In some example embodiments the sintered cemented carbide insert 2 further comprises a metal (M) selected from one or more of titanium, vanadium, niobium, zirconium or tantalum in an amount such that the ratio of binder composition is ((wt% M) / (wt% Fe + wt% Ni + wt% Co)) * 1000 = 0.1 - 0.95. For example ((wt% M) / (wt% Fe + wt% Ni + wt% Co)) * 1000 = 0.1 - 0.35. For example, ((wt% M) / (wt% Fe + wt% Ni + wt% Co)) * 1000 = 0.1 - 0.25. If a mixture of titanium, vanadium, niobium, zirconium or tantalum is used, the wt% M refers to the total wt% of the mixture of metals.

[0025] For example, if 0.02 wt% Ti, 50 wt% Fe, 25 wt% Ni and 24.98 wt% Co is used the ratio of binder composition is ((0.02) / (50 + 25 + 24.98)) * 1000 = 0.20

[0026] In other words, the sintered cemented carbide insert 2 further comprises between 100 - 950 wt ppm titanium, vanadium, niobium, zirconium or tantalum. For example, between 100 - 350 wt ppm titanium, vanadium, niobium, zirconium or tantalum. For example, between 100 - 250 wt ppm ppm titanium, vanadium, niobium, zirconium or tantalum. This would be measured using for example Inductively Coupled Plasma - Optical Emission Spectrometry (ICP-OES) analysis.

[0027] If the cemented carbide comprises titanium, vanadium, niobium, zirconium or tantalum, this is included as part of the composition of the binder, i.e. the total binder phase content is calculated according to wt% Fe + wt% Ni + wt% Ti + wt% Ta + wt% Nb + wt% Zr + wt% V and a balance of Co.

[0028] In cobalt based cemented carbides for rock drilling the binder phase work hardens during post sintering treatments, such as tumbling, or during drilling. FeNiCo based binders also have the ability to undergo a phase transformation, which is known as martensite transformation. The martensitic transformation temperature is heavily dependent on the carbon content of the binder, and the carbon content is not easily controllable during the manufacturing of alternative binders which means that the work hardening phase change will not always take place during post sintering treatments such as tumbling or during drilling as desired. The addition of small amounts of one or more of titanium, vanadium, niobium, zirconium or tantalum, which are cubic carbide formers, and will enable the carbon content to be controlled. These additions will form MC carbides which acts as carbon getters during cooling in the sintering cycle as they become more stoichiometric at lower temperatures. This effect drains the binder phase of carbon and controls the martensite transformation temperature, this means that the phase transformation will reliably occur during post-sintering treatment and / or during drilling which will lead to work hardening and therefore provide inserts having an improved wear resistance. Martensite can be observed using scanning electron microscope (SEM) after etching. Another effect of the additions of one or more of Ti, Ta, Nb, V or Zr is that the WC grain growth during sintering is inhibited, resulting in less abnormal grain growth and thus has higher sinter stability compared to a material without this addition. It is preferred that the quantity of the cubic carbide former is controlled so the MC formed is present only small amounts in the binder phase or form atomic layers at the WC interfaces and no bulk MC is precipitated.

[0029] In some example embodiments, the Ta, V, Nb, Ti is slightly soluble in the WC.

[0030] In some example embodiments the sintered cemented carbide insert comprises < 2 area % MC -phase measured with binary image analysis using scanning electron microscopy wherein 10 random areas are assessed and an average area % calculated. For example, < 1 area % MC-phase, for example < 0.800 area%. For example, between 0.031 - 0.556 area %, for example 0.036 - 0.500 area %. In another embodiment the cemented carbide insert is substantially free of MC-phase. Substantially free of MC-phase herein means < 0.500 area % MC-phase. If you have too much cubic phase the material will become brittle.

[0031] In some example embodiments, M is titanium, tantalum or niobium or a mixture thereof which will enhance WC-WC grain boundary strength. Advantageously, these metals do not precipitate embrittling phases at the WC-binder interfaces which would have a negative impact on fracture toughness.

[0032] In some example embodiments the Vickers hardness in the bulk of the inserts is between 800-1750 HV20 measured according to ISO EN6507. For example, between 900 - 1650 HV20, for example between 1000 - 1600 HV20. This range provides the most optimal balance between wear resistance and fracture toughness.

[0033] In some example embodiments the Vickers hardness in the bulk of the inserts is between 800-1750 HV3 measured according to ISO EN6507. For example, between 900 - 1650 HV3, for example between 1000 - 1600 HV3. This range provides the most optimal balance between wear resistance and fracture toughness.

[0034] In some example embodiments, the difference between an average hardness at 0.3 mm below the surface of the insert and an average hardness in the bulk of the insert is at least 15 HV3 wherein hardness is measured according to ISO EN6507. For example, at least 18 HV3, for example at least 20 HV3. Advantageously, this will provide an insert having a harder, more wear resistant surface and a tougher core.

[0035] In some example embodiments, the % change in average hardness at 0.3 mm below the surface of the insert compared to the average hardness in the bulk of the insert is at least 1%, for example at least 1.5 %, for example at least 2%. Advantageously, this will provide an insert having a harder, more wear resistant surface and a tougher core.

[0036] In some example embodiments the sintered cemented carbide inserts are free of chromium, for example <0.5 wt% Cr, for example <0.1 wt% Cr, for example <0.05 wt% Cr. In some example embodiments, the sintered cemented carbide inserts are uncoated.

[0037] Another aspect of the present application relates to a method of producing a cemented carbide insert as disclosed hereinbefore or hereinafter, comprising the steps of: a) providing a powder mixture comprising between 4-18 wt% binder, any unavoidable impurities and a balance of WC; b) compacting the powder mixture to form a green cemented carbide insert; c) sintering the green carbide mining insert to form a sintered cemented carbide insert; d) subjecting the sintered cemented carbide insert to a tumbling treatment; wherein the binder comprises 48-52 wt% iron, 23-27 wt% nickel as a proportion of the total binder content and a balance of cobalt.

[0038] In some example embodiments, the binder phase comprises 49-51 wt% iron as a proportion of the total binder content, for example 50 wt%.

[0039] In some example embodiments, the binder phase comprises 24 - 26 wt% nickel as a proportion of the total binder content, for example 25 wt%.

[0040] In some example embodiments, in step a) the powder mixture further comprises 100 - 950 wt ppm addition of titanium, vanadium, niobium, zirconium or tantalum or a mixture thereof. For example, between 100 - 350 wt ppm addition of titanium, vanadium, niobium, zirconium or tantalum or a mixture thereof. For example, between 100 - 250 wt ppm addition of titanium, vanadium, niobium, zirconium or tantalum or a mixture thereof.

[0041] In some example embodiments, the tumbling treatment is a “High Energy Tumbling” process, wherein post tumbling a homogenous cemented carbide mining insert has been deformation hardened such that the change in HV3 between the surface and the bulk is at least 1.5 %. References in the description to “one embodiment,” “an embodiment,” “an example embodiment,” “for example” 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.

[0042] Examples

[0043] Example 1 - Samples

[0044] Table 1 shows the summary of the weight in composition and WC grain size of the samples tested. The compositions of the cemented carbide were made so that the calculated mole fractions of the binder content were similar for both the comparative and inventive samples (hence why the binder wt% is slightly different).

[0045] The samples shown in table 1 were prepared by milling in a ball mill in wet conditions, using ethanol, with an addition of 2 wt% polyethylene glycol (PEG 80), in excess of the powder mass, as organic binder (pressing agent) and cemented carbide milling bodies. After milling, the mixture was spray-dried in N2-atmosphere and then uniaxially pressed into GT7S100A mining inserts having a size of about 10 mm in outer diameter (OD) and about 16-20 mm in height with a weight of approximately 17g each with a spherical dome (“cutting edge”) on the top. The samples were then sintered using Sinter-HIP in 55 bar Ar- pressure at 1410°C or 1500 °C for 1 hour.

[0046] Post sintering, the inserts were shaken in a commercially available paint shaker of trademark Corob™ to represent a labscale high energy tumbling process.

[0047] Table 1: Summary of samples Table 2: measured carbon content

[0048] The WC-grain size was determined using EBSD on a cross-section of an ion polished sintered sample (settings in table 3). The average WC grain size is determined by using the area weighted equivalent circle diameter. The analysis is performed with the bulk of the samples un-effected by the tumbling process.

[0049] Settings and method for EBSD analysis on WC grain size were:

[0050] Table 3. Settings for the EBSD analysis in Aztec 6.0.

[0051] The post-processing was performed using AztecCrystal 2.2 software. For WC, autocleaning 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, where the pixel size equals the step size.

[0052] The total carbon (C) content of the composite is measured for selected composition (table 2) using chemical analysis LECO - CS844 instrument.

[0053] Example 2 - Insert compression test

[0054] 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 fracture 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 pm / 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.

[0055] Both as sintered (AS) samples and samples exposed to the high energy tumbling process described in example 1 was tested. Three inserts were tested per run with the average reported. 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 material strength was characterized by means of the total absorbed deformation energy until fracture. The summary fracture energy (Ec), in Joules (J), required to crush the samples is shown in table 4 below:

[0056] Table 4: Crush test results

[0057] It can be seen that the inventive sample have a higher difference between AS and tumbled sample than the comparative sample having a cobalt binder phase (and the same WC grain size).

[0058] Example 3 - Hardness measurements after post treatment

[0059] The hardness of the tumbled cemented carbide inserts is measured using Vickers hardness 3 kg. The measurement is performed indenting a contour around the sample 0.3 mm from the surface and as a contour in the bulk of the inserts. The hardness measurements are an average the contour with 88-89 indents for the surface value and 29-32 indentations for the bulk value, shown in table 5.

[0060] Table 5: Hardness measurements

[0061] It can be seen that the inventive and comparative samples have similar change in hardness after tumbling.

[0062] Example 4 - Wear test

[0063] As sintered 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: 200 N load applied to each insert, granite log rpm -270, 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 200 m and the mass loss versus sliding distance was approximately linear between the samples of each grade that was tested. The sample was cooled by a continuous flow of water.

[0064] To account for variations within the rock, a reference sample from the same batch is consistently included. This allows results to be normalized against the reference, facilitating comparison across different runs and segments of the rock. In this example, Sample A serves as the reference, and all data will be normalized accordingly.

[0065] Each sample was carefully cleaned and weighed prior to and after the test. Mass loss of three samples 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 6.

[0066] Table 6: Wear test results

[0067] It can be seen that the wear rate is reduced for the inventive sample compared to the comparative samples. Both sample B and C have same WC grain size. However, sample B hasve lower binder content which should result in better wear properties but surprisingly this is not the case.

[0068] Example 5 - Fracture toughness

[0069] The fracture toughness has been evaluated by measuring the total crack length from the four corners of an indentation mark using Vickers indentation of 30 kg. For cobalt containing cemented carbides Palmqvist fracture toughness (Wk) can be calculated as: Wk= A H PTT, where A is an empirical constant with a value of 0.0028 evaluated for WC-Co cemented carbides, H is the Hardness in (N / mm2), P is the load, and T is the total crack length. As changing the binder composition and thereby material properties such as Young's modulus and Poisson's ratio of the binder and how this effects this constant is unknown. Hence, as they total crack length will be inversely proportional to the Palmqvist fracture toughness this is used as fracture toughness evaluation, i.e. shorter crack length means a tougher material. This is applied in the two examples below.

[0070] Fracture toughness bulk

[0071] The fracture toughness was evaluated in the bulk of the samples from measuring the total crack lengths from Vickers indentation using 30 kg on 10 mm in diameter spherical domed samples. The samples were sectioned in half through the dome area, mounted in Bakelite, polished with diamond paste and the crack length and diameter of 3-5 indentations in the bulk evenly distributed at least 0.75 mm apart. The diameter of the indentations and the length of the cracks were measured using light optical microscope and 200 X magnification. The average total crack length from the 3-5 indentation marks is listed in table 7.

[0072] Table 7: measured total crack length

[0073] It can be seen that for samples with similar WC grain size but different binder chemistry, sample C and D exhibit a shorter total crack length than sample A, which contains a cobalt binder phase. Additionally, samples C and D, both with Ti added, display shorter crack lengths compared to sample B and E, both without Ti added. In this comparison all samples have similar WC grain sizes showing that it is the Ti addition resulting in shorter cracks and improved fracture toughness.

[0074] Fracture toughness after post treatment

[0075] The difference in fracture toughness comparing top and bulk of the inserts was evaluated of the tumbled samples. This was done from measuring the total crack lengths from Vickers indentation using 30 kg on 10 mm in diameter spherical domed samples. The samples were sectioned in half through the dome area, mounted in Bakelite, polished with diamond paste before measurements. The diameter of the indentations and the length of the cracks were measured using light optical microscope and 200 X magnification. The total crack length of an indentation 0.5 mm below the top surface and 6.5 mm from the top surface was compared. The total crack length from the four corners of the indentation mark as well as the relative difference between top and bulk is compared in Table 8.

[0076] Table 8: measured total crack length 0,5 and 6,5 mm from top and the

[0077] It can be seen that the change in total crack length between the top and bulk is larger for the inventive sample C compared to the comparative sample B.

[0078] Example 6 - Field trial

[0079] Table 9 shows the results from a wet underground top hammer application test. Spherically shaped inserts with a diameter of 10 mm were tested and mounted in a steel bit having six inserts on the periphery / gauge and three inserts on the front. Prior to mounting the inserts, they were ground on the cylindrical part and tumbled according to the description in example 1. The inventive inserts were positioned in the gauge, the front inserts had the comparative grade composition. The bits (7581-4348A-S) were tested in an underground mine in the north of Sweden. The rock conditions were classified as “very abrasive”. Before drilling started the average diameter of each bit was measured. Each bit was drilled until the penetration rate decreased; this corresponds with the inserts having a wear flat of approximately l / 3rdof the diameter of the insert. The average diameter of the bit was then measured again and the difference in diameter was evaluated as average diameter wear from drilling.

[0080] Table 9: Field trial results

[0081] It can be seen that the inventive sample has an improved performance in the field.

[0082] Example 7 X-ray diffraction

[0083] The samples were analysed using X-ray diffraction on the on the top of the as-sintered and tumbled samples. The X-ray source was operated at 50 kV, 1 mA and a collimator size of 0.5 mm diameter was used for both analyses. The drill bit inserts were mounted with adhesive tape to the sample holder. Data were typically collected in the 2 9 range 33°-55°. Specific attention was paid to the region between 29 = 42° and 29 = 46° where the (111) peak of austenite and (110) peak of martensite can be expected respectively. The XRD data were analyzed with software DIFFRAC.EVA (Bruker) and HighScore Plus (Malvern P analytical).

[0084] Figure 2 shows the X-ray diffraction plot for sample C for the as sintered (AS) and tumbled samples. It can be seen that the inventive as sintering sample only show an FCC binder phase (peak between 43-44 29), whereas after tumbling a BCC martensite reflection can also be identified between 44.5-45.5 29. Hence, a deformation induced phase transformation has occurred within the material after tumbling.

Claims

Claims1. A sintered cemented carbide insert (2) for rock mining or rock cutting applications comprising binder phase and a balance of tungsten carbide hard phase; wherein the binder phase content of the cemented carbide is between 4-18 wt%; wherein the average tungsten carbide grain size is between 0.8 - 15 pm measured using EBSD; wherein binder phase comprises between 48-52 wt% iron, 23-27 wt% nickel as a proportion of the total binder phase; and a balance of cobalt; wherein the difference between an average hardness at 0.3 mm below the surface of the insert and an average hardness in the bulk of the insert is at least 15 HV3 wherein hardness is measured according to ISO EN6507; characterized in that: the binder further comprises a metal (M) selected from one or more of titanium, vanadium, niobium, zirconium or tantalum in an amount such that the ratio of the binder composition is ((wt% M) / (wt% Fe + wt% Ni + wt% Co)) * 1000 = 0.1 - 0.95.

2. The sintered cemented carbide insert (2) according to claim 1 wherein the binder further comprises a metal (M) selected from one or more of titanium, vanadium, niobium, zirconium or tantalum in an amount such that the ratio of the binder composition is ((wt% M) / (wt% Fe + wt% Ni + wt% Co)) * 1000 = 0.1 - 0.35.

3. The sintered cemented carbide insert (2) according to claim 1 or claim 2 wherein the binder further comprises a metal (M) selected from one or more of titanium, vanadium, niobium, zirconium or tantalum in an amount such that the ratio of thebinder composition is ((wt% M) / (wt% Fe + wt% Ni + wt% Co)) * 1000 = 0.1 - 0.25.

4. The sintered cemented carbide insert (2) according to any of the previous claims wherein the binder phase content of the cemented carbide is between 5 - 14 wt%.

5. The sintered cemented carbide insert (2) according to any of the previous claims wherein binder phase comprises between 49 - 51 wt% iron, 24 - 26 wt% nickel as a proportion of the total binder phase; and a balance of cobalt.

6. The sintered cemented carbide insert (2) according to any of the previous claims comprising < 2 area % MC -phase measured with binary image analysis using scanning electron microscopy.

7. The sintered cemented carbide insert (2) according to claim 4 wherein M is selected from one or more of titanium, tantalum or niobium.

8. The sintered cemented carbide insert (2) according to any of the previous claims wherein the Vickers hardness in the bulk of the inserts us between 800-1750 HV20 measured according to ISO EN6507.

9. A method of producing a cemented carbide insert according to any of claims 1-8, comprising the steps of: a) providing a powder mixture comprising between 4-18 wt% binder and a balance of WC; b) compacting the powder mixture to form a green cemented carbide insert; c) sintering the green carbide mining insert to form a sintered cemented carbide insert; d) subjecting the sintered cemented carbide insert to a tumbling treatment; characterised in that:the binder phase comprises 48-52 wt% iron, 23-27 wt% nickel as a proportion of the total binder content; 100 - 950 wt ppm of titanium, vanadium, niobium, zirconium or tantalum or a mixture thereof and a balance of cobalt.

10. The method according to claim 9 wherein the binder phase comprises between 100- 350 wt ppm of titanium, vanadium, niobium, zirconium or tantalum or a mixture thereof.

11. The method according to claim 9 or 10 wherein the binder phase comprises between 100- 250 wt ppm of titanium, vanadium, niobium, zirconium or tantalum or a mixture thereof.

12. The method according to any of claims 9-11, wherein the tumbling treatment is a “High Energy Tumbling” process, wherein post tumbling a homogenous cemented carbide mining insert has been deformation hardened such that the change in HV3 between the surface and the bulk is at least 1.5 %.

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