Cutting Tools

Abstract

The present invention relates to a cutting tool comprising a substrate of cemented carbide, wherein the cemented carbide comprises hard constituents in a metallic binder. The hard constituents comprise WC, and the WC content in the cemented carbide is 80 wt% to 95 wt%. The cemented carbide has a Fe+Ni+Co+Cr content of 3 wt% to 13 wt% and an atomic ratio of 0.05 < Fe / (Fe+Ni+Co+Cr) < 0.35 and an atomic ratio of 0.05 < Ni / (Fe+Ni+Co+Cr) < 0.35 and an atomic ratio of 0.05 < Co / (Fe+Ni+Co+Cr) < 0.35 and an atomic ratio of 0.05 < Cr / (Fe+Ni+Co+Cr) < 0.35. The fracture resistance W is defined as the load of the Vickers indentation divided by the total length of the cracks formed at the edge of the Vickers indentation. The W measured on the rake face of the cutting tool is at least 25% higher than the W measured on the cross-section of the body region of the cutting tool.

Description

Technical Field

[0001] The present invention relates to a cutting tool of cemented carbide, wherein the cemented carbide comprises a metal binder and a hard component containing WC. The surface area of ​​the cutting tool has a higher crack resistance than the body area of ​​the tool. Background Art

[0002] Cutting tools for metal cutting applications generally comprise a matrix of cemented carbide. Cemented carbide is a material that shows both high hardness and high toughness and has been successful for decades in performance in cutting applications. In order to further improve the performance of cutting tools, it is known to coat the tool with a wear-resistant coating. It is also known to process cutting tools in a process called post-processing, which includes steps such as wet blasting, dry blasting, blade brushing and / or polishing. These post-processing processes generally change the surface roughness of cutting tools and / or the residual stress in the surface area of ​​cutting tools.

[0003] Wang et al., “Effect of shot peening on the residual stresses and microstructure of tungsten cemented carbide”, Materials and Design 95, 2016, pp. 159-164, describes the effect of shot peening of cemented carbide. It shows that compressive residual stresses are induced in the surface layer, both in Co and WC.

[0004] There is a continuous need to improve the life and performance of cutting tools to save manufacturing time and reduce the risk of failure due to cutting tool breakage. There is also a need to reduce the amount of Co in cemented carbides and find alternative cemented carbides that can compete with traditional Co-containing cemented carbides in terms of metal cutting performance. Summary of the invention

[0005] The object of the present invention is to provide a cutting tool with improved wear resistance in metal cutting applications, and the object of the present invention is also to provide a method for manufacturing the cutting tool. Another object of the present invention is to provide a cutting tool with high resistance to chipping of the coating at the cutting edge. Another object is to provide a turning tool with increased resistance to chipping of the cutting edge and / or breakage of the cutting tool.

[0006] At least one of these objects has been achieved by the cutting tool of item 1 and the method of item 12. Preferred embodiments are disclosed in the dependent claims.

[0007] The present invention relates to a cutting tool comprising a substrate of cemented carbide, wherein the cemented carbide comprises hard constituents in a metallic binder, wherein the hard constituents comprise WC, and wherein the WC content in the cemented carbide is from 80 wt% to 95 wt%, and wherein the cemented carbide has an Fe+Ni+Co+Cr content of from 3 wt% to 13 wt% and an atomic ratio of 0.05 < Fe / (Fe+Ni+Co+Cr) < 0.35 and an atomic ratio of 0.05 < Ni / (Fe+Ni+Co+Cr) < 0.35 and an atomic ratio of 0.05 < Co / (Fe+Ni+Co+Cr) < 0.35 and an atomic ratio of 0.05 < Cr / (Fe+Ni+Co+Cr) < 0.35, the cutting tool comprising a rake face, a flank face and a cutting edge therebetween, and wherein the crack resistance W is defined as

[0008]

[0009] where P is the load of the Vickers hardness indentation 100*9.81 N, and ā is the average crack length of each crack formed at the corners of the Vickers hardness indentation, and wherein W measured on the rake face of the cutting tool is at least 25% higher than W measured on the cross-section of the body region of the cutting tool.

[0010] The above composition ranges enable the binder to obtain a large solid solution hardening effect, which results in a high hardness that is good for wear resistance and resistance to plastic deformation. However, in order to have good metal cutting properties, a good combination of toughness and resistance to plastic deformation is required. Generally for most technical composites such as cemented carbides, an increase in toughness is associated with a decrease in hardness. It has unexpectedly been found that by processing materials with specific composition ranges according to the present invention, a crack resistance on the rake face that is more than 25% higher than that of the body is achieved. Cracks formed in the cutting tool during metal cutting usually originate from the rake side of the cutting tool, and these cracks limit the tool life. Therefore, increasing the crack resistance on the rake face will extend the tool life of the cutting tool in metal cutting applications.

[0011] In one embodiment of the present invention, the cemented carbide comprises x wt% Ni, y wt% Fe, z wt% Co and v wt% Cr, and wherein 5 < x + y + z + v < 9. Cemented carbides within this binder content range have a good combination of toughness and resistance to plastic deformation suitable for cutting tool applications. Depending on the metal cutting application, the amount of binder can be optimized by those skilled in the art.

[0012] In one embodiment of the present invention, the residual stress measured in the surface area on the rake face of the cutting tool is compressive residual stress and > 2000 MPa, preferably > 2200 MPa, more preferably 2400 MPa to 2800 MPa, where the stress measurement is carried out using X-ray diffraction and the sin 2 ψ method with the (2 1 1) reflection of WC. The compressive residual stress inhibits crack formation. Therefore, increasing the crack resistance on the rake face will extend the tool life of the cutting tool in metal cutting applications.

[0013] In one embodiment of the present invention, the relationship between the crack resistance W (W(rake face)) measured on the rake face and the crack resistance W (W(flank face)) measured on the flank face is W(rake face) / W(flank face) > 1.10. Cracks formed during metal cutting usually originate from the rake side of the cutting tool. Therefore, good crack resistance on the rake face is beneficial for metal cutting applications. Additionally, if only the rake face is shot peened, the cutting tool manufacturing process will be relatively simple and the flank side will be slightly less prone to cracking.

[0014] In one embodiment of the present invention, the hardness at the surface of the cutting tool > 1500 HV100, preferably > 1600 HV100. An increased hardness in the surface area of the cutting tool, especially in the area of the cutting tool that contacts the workpiece material during metal cutting applications, is beneficial because the wear resistance of the cemented carbide increases. In addition, the coating applied to the substrate can withstand use for a longer time on a harder substrate, thereby increasing the life of the cutting tool.

[0015] In one embodiment of the present invention, the cemented carbide has an atomic ratio of 0.2 < Fe / (Fe + Ni + Co + Cr) < 0.3 and an atomic ratio of 0.2 < Ni / (Fe + Ni + Co + Cr) < 0.3 and an atomic ratio of 0.2 < Co / (Fe + Ni + Co + Cr) < 0.3 and an atomic ratio of 0.2 < Cr / (Fe + Ni + Co + Cr) < 0.3. This composition range enables the binder to obtain an almost maximum solution hardening effect, which results in a high hardness that is good for wear resistance and resistance to plastic deformation.

[0016] In one embodiment of the present invention, the WC grain size is uniform throughout the substrate. Non-uniform WC grain size can lead to crack initiation sites due to differences in the thermo-mechanical properties of different regions.

[0017] In one embodiment of the present invention, the average WC grain size is 0.2 μm to 10 μm, preferably 0.5 μm to 3 μm. Within this range, the WC grain size is optimal for cemented carbide targeted at metal cutting inserts. Depending on the metal cutting application, those skilled in the art can optimize the WC grain size.

[0018] In one embodiment of the present invention, the cemented carbide further comprises one or more of Cu, W, Mo, Mn, Al, and Si. These elements provide strengthening of the cemented carbide through solid solution hardening.

[0019] In one embodiment of the present invention, the cemented carbide further comprises one or more of Ta, Nb, Ti, Zr, Hf, and V. These elements tend to form cubic carbides in the cemented carbide. Cutting tools with cubic carbides have increased bulk high temperature hardness. These elements are also used to produce gradient zones poor in such cubic carbides. A gradient zone poor in such cubic carbides is advantageous because it provides increased crack growth resistance in the surface region while maintaining good bulk plastic deformation resistance that is advantageous for some turning inserts.

[0020] In one embodiment of the present invention, the matrix of the cemented carbide comprises a cubic phase, and wherein the matrix of the cemented carbide is provided with a surface zone poor in the cubic phase, the thickness of the surface zone is 2 μm to 100 μm, preferably 3 μm to 70 μm, more preferably 8 μm to 35 μm.

[0021] In one embodiment of the present invention, the cemented carbide substrate is provided with a coating, preferably comprising a coating selected from TiN, TiCN, TiC, TiAlN, Al 2 O 3 and ZrCN, more preferably a coating having a thickness of 2 μm to 20 μm.

[0022] In one embodiment of the invention, the hardness in the surface area of ​​the cutting tool is the same as the hardness in the body area, with a deviation of 10%. Cemented carbide with uniform hardness in the body and surface is economical for large-scale manufacturing. According to the present invention, hard cemented carbide can then become more resistant to crack formation on the surface.

[0023] The present invention relates to a method of treating a cutting tool comprising a cemented carbide substrate, wherein the cemented carbide comprises hard constituents in a metallic binder, wherein the hard constituents comprise WC, and wherein the WC content in the cemented carbide is 80 wt% to 95 wt%, wherein the cemented carbide has an Fe+Ni+Co+Cr content of 3 wt% to 13 wt% and an atomic ratio of 0.05 < Fe / (Fe+Ni+Co+Cr) < 0.35 and an atomic ratio of 0.05 < Ni / (Fe+Ni+Co+Cr) < 0.35 and an atomic ratio of 0.05 < Co / (Fe+Ni+Co+Cr) < 0.35 and an atomic ratio of 0.05 < Cr / (Fe+Ni+Co+Cr) < 0.35, wherein the cutting tool (1) is subjected to shot peening at a temperature equal to or higher than 100 °C, preferably at a temperature equal to or higher than 200 °C, more preferably at a temperature between 200 °C and 600 °C. The shot peening of the present invention is carried out at an elevated temperature in one embodiment, and this temperature is herein defined as the temperature at which the material (part of the cutting tool) being shot peened is during the shot peening. Various methods can be used to generate the elevated temperature of the cutting tool part, such as induction heating, resistance heating, preheating on a hot surface / furnace, laser heating, etc. Alternatively, the cutting tool can be heated in a separate step before the shot peening step.

[0024] The temperature is suitably measured on the substrate by any suitable method for measuring temperature. Preferably, an infrared temperature measuring device is used.

[0025] The part of the substrate subjected to shot peening is at said temperature. It has been unexpectedly found that treating the cutting tool with shot peening when heating the cutting tool increases its crack resistance in the surface area, which is an important property for increasing the cutting tool life.

[0026] In one embodiment of the present invention, the cutting tool (1) comprises a rake face (2), a flank face (3) and a cutting edge therebetween, and wherein the shot peening is carried out at least on the rake face (2). Cracks formed in the cutting tool during metal cutting usually originate from the rake side of the cutting tool, and these cracks limit the tool life. Therefore, increasing the crack resistance on the rake face will extend the tool life of the cutting tool in metal cutting applications.

[0027] In one embodiment of the present invention, the ER of at least a part of the cutting edge is between 10 μm and 50 μm, preferably between 20 μm and 40 μm. It has been surprisingly found that the cutting tool manufactured according to the method of the present invention performs well when the cutting tool has this ER.

[0028] In one embodiment of the invention, the shot peening is performed on a heated cutting tool, the method comprising a step prior to the shot peening, wherein the cutting tool is heated. Heating the cutting tool prior to the shot peening may be advantageous, as heating typically takes longer than applying the shot peening.

[0029] In one embodiment of the invention, the method further comprises the step of shot blasting at least a portion of the cutting tool, wherein the step of shot blasting is performed after the shot peening. This is advantageous because shot blasting provides compressive stress on the upper part of the coating, and this in combination with shot peening is advantageous for tool life.

[0030] Other objects and features of the present invention will become apparent from the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In the attached picture:

[0032] Figure 1 is a schematic diagram of a cutting tool insert 1, which is provided with a rake face 2, a flank face 3 and a cutting edge disposed therebetween, and

[0033] Figure 2 is a schematic diagram of a cross section of a cutting edge, in which the cutting edge rounding (ER) is shown, and the width A of the cutting edge is also schematically shown.

[0034] definition

[0035] "Cemented carbide" is a material comprising a hard component distributed in a continuous metal binder, the hard component forming a skeleton embedded in the continuous metal binder. The hard component mainly comprises WC. This material has the properties of combining high hardness from the hard component and high toughness from the metal binder, and is suitable as a matrix material for metal cutting tools.

[0036] The "composition" or "content" of cemented carbide herein means the average composition or average content in the cemented carbide matrix. For example, a gradient in a surface region of, for example, 15 μm to 30 μm from the substrate surface toward the body with a locally higher metal binder content does not change the average composition of the cemented carbide matrix of the cutting tool, because the size of the cutting tool is at least several millimeters.

[0037] The "metal binder" of cemented carbide may contain other elements that dissolve in the metal binder during sintering, such as W and C from WC. Other elements may also dissolve in the binder, depending on what other types of hard constituents are present.

[0038] "Cutting tool" in this context means a cutting tool used for metal cutting applications, such as an insert, end mill or drill. The application area may be turning, milling or drilling.

[0039] "ER" is a value of the cutting edge rounding intended to indicate the sharpness of a cutting edge. A larger ER value represents a rougher shaped cutting edge, while a smaller ER value represents a sharp cutting edge.

[0040] ER is defined in this paper as the value calculated according to:

[0041] - Placing the cutting tool with its support surface or a corresponding surface of said cutting tool on a flat surface.

[0042] - aligning a first face perpendicular to the flat surface in contact with the cutting edge to be measured along one side of the cutting tool, for example along the flank face 3 of the cutting tool 1,

[0043] - aligning a second face parallel to the flat surface and intersecting the first face at an intersection point, the second face being in contact with the cutting edge to be measured at the contact point, for example aligning the second face along the rake face 2 of the cutting tool 1 .

[0044] The value "ER" is equal to the distance between the intersection point between the first face and the second face and the contact point between the first face and the cutting tool close to the cutting edge, see Figure 2 .

[0045] "Shot peening" refers herein to a process using abrasive particles, wherein material is removed from the treated surface, usually by abrasive wear. Shot peening is well known in the cutting tool art and is, for example, known to introduce residual stresses in coatings on cutting tools.

[0046] "Shot peening" means in this context that the surface of a cutting tool is bombarded with a medium containing particles (so-called beads) which are non-abrasive and generally have a rounded shape. The medium may be beads of a hard material such as oxide, steel or cemented carbide.

[0047] The term "body" herein means the innermost part (center) of the cutting tool.

[0048] The term "surface area" is used herein to refer to the exterior of a substrate that is affected by the shot peening process disclosed herein.

[0049] Other embodiments of the present invention

[0050] In one embodiment of the invention, the cemented carbide further comprises a cubic phase, sometimes referred to as a γ phase, which is a solid solution of cubic carbides and / or carbonitrides of one or more elements selected from Ti, Ta, Nb, Hf, Zr, V and Cr. The amount of the cubic phase (in area %) is suitably 2% to 25%, preferably between 3% and 15%. This can be measured in different ways, but one method is to perform image analysis on an optical microscope image or a scanning electron microscope (SEM) micrograph of a cross section of the substrate to calculate the average fraction of the γ phase.

[0051] In one embodiment of the present invention, the cemented carbide comprises a cubic phase and a surface zone rich in a cubic phase and rich in a binder phase. The thickness of the surface zone is suitably 2 μm to 100 μm, preferably 3 μm to 70 μm, and more preferably 8 μm to 35 μm. The thickness is determined by measuring on a SEM or LOM image of a cross section of the substrate. These measurements should be made in a moderately flat area on the substrate surface, i.e., not close to a cutting edge, at least 0.3 mm from a cutting edge or a tip, in order to obtain a true value. The boundary between the surface zone and the body is determined by the absence / presence of a cubic phase, which is usually quite obvious when observing a cross section of the substrate in an SEM or LOM image. The thickness is determined by the distance between the surface and the boundary between the surface zone and the body. Rich in binder means in this article that the binder phase content in the surface zone is suitably 1.05 to 1.65 times, preferably 1.1 to 1.5 times, of the binder phase content in the body. The binder phase content in the surface zone is suitably measured at half the depth of the total thickness / depth of the surface zone. All measurements made on the bulk should be made at an area not too close to the surface area. This means in this context that any measurement of the microstructure of the bulk should be made at a depth of at least 200 μm from the surface.

[0052] A surface region depleted of cubic phase means herein that the surface region contains no or very few (ie, less than 0.5 area %) cubic phase particles.

[0053] In one embodiment of the present invention, the cutting tool is provided with a coating, which may be a coloring layer or a wear-resistant coating.

[0054] In one embodiment of the present invention, the thickness of the coating is 2 μm to 20 μm, preferably 5 μm to 10 μm.

[0055] In one embodiment of the present invention, the cutting tool comprises a coating, and wherein the coating thickness in the hardness measurement region is 3 μm to 12 μm, preferably less than 6 μm.

[0056] In one embodiment of the present invention, the coating is a CVD coating or a PVD coating, and preferably the coating comprises a material selected from TiN, TiCN, TiC, TiAlN, Al 2 O 3 and one or more layers of ZrCN. The coating preferably comprises a TiCN layer and an Al 2 O 3 layer of CVD coating.

[0057] In one embodiment of the present invention, the coating is a CVD coating comprising an inner TiCN layer and an outer α-Al 2 O 3 layer.

[0058] In one embodiment of the present invention, the cemented carbide substrate is provided with a wear resistant PVD coating, suitably a nitride, oxide, carbide or mixture thereof of one or more elements selected from Al, Si and elements of Groups 4, 5 and 6 of the periodic table.

[0059] In one embodiment of the invention, the cutting tool comprises a rake face, a flank face and a cutting edge therebetween, and wherein the shot peening is performed at least on the rake face. Shot peening of the rake face is advantageous because during the cutting operation, the working material strikes the cutting tool at the rake face, so that during the shot peening, the mechanism affecting the substrate is applied at the relevant area or volume of the substrate. Applying shot peening at the rake face is further advantageous because for many cutting tool geometries this means treating multiple cutting edges simultaneously.

[0060] In one embodiment of the present invention, the shot peening is performed with ceramic beads, preferably with ceramic beads containing ZrO 2 、SiO 2 and Al 2 O 3 of beads.

[0061] In one embodiment of the present invention, the shot peening is carried out with a shot peening medium having an average diameter of 70 μm to 150 μm. If the beads are too large, the risk of damaging the cutting edge increases. If the beads are too small, the energy and impact transferred from the medium to the substrate are less obvious. The impact or energy from the beads during shot peening should not be too high, as this will increase the risk of damaging the surface and cutting edge of the cutting tool. The impact or energy from the beads should not be too low either, as that would not achieve the technical effect. If the beads are too large, the risk of damaging the cutting edge increases. If the beads are too small, the energy and impact transferred from the medium to the substrate are less obvious. The appropriate size of the beads is related to the material of the beads and is selected by a person skilled in the art.

[0062] In one embodiment of the invention, the shot peening is performed on a heated cutting tool, the method comprising a step prior to the shot peening in which the cutting tool is heated.

[0063] In one embodiment of the present invention, the method further comprises the step of shot blasting at least a portion of the cutting tool. Preferably, the portion comprises at least a portion of the cutting edge or an area close to the cutting edge.

[0064] In one embodiment of the present invention, the shot blasting step is performed after shot peening. The heat during shot peening may reduce some of the positive effects from shot peening, such as inducing residual stress in the coating, so by choosing to perform shot peening before shot peening, the positive effects of both can be maintained.

[0065] In one embodiment of the invention, the shot blasting and the shot peening are performed on the same part of the cutting tool. This is advantageous, for example, during large-scale manufacturing, since the cutting tool is loaded more efficiently.

[0066] In one embodiment of the present invention, the shot peening is performed in a shot direction perpendicular to the surface of the cutting tool. Vertical shot peening is advantageous because the depth of the impacted substrate is maximum when the heated shot peening is in this direction.

[0067] In one embodiment of the present invention, the cutting tool 1 is an insert, preferably a milling insert or a turning insert.

[0068] The shot peening process according to the invention may also be combined with other process steps known in the art for manufacturing cutting tools, such as brushing, polishing, wet blasting, dry blasting, etc. Example

[0069] Exemplary embodiments of the present invention will now be disclosed in more detail and compared with reference embodiments. Coated cutting tools (inserts) were prepared and analyzed.

[0070] Example 1 (Sample Preparation)

[0071] The cemented carbide substrate was prepared from the following raw material powders: 0.76 wt% TiC, 0.50 wt% NbC, 2.9 wt% TaC, 1.52 wt% Ti(C,N), 0.02 wt% carbon black and the balance WC. The average grain size (FSSS) of WC was 4 μm. The elements Co, Cr, Fe and Ni were 0.99 wt% Co, 2.02 wt% Cr and 1.52 wt% Ti(C,N). 3 C 2 , 4.85 wt% Fe 0.4 Ni0.4 Co 0.2 Add. The amount of each raw material is based on the total dry powder weight. The amount of elements Co, Ni, Fe and Cr is calculated with the CoCrFeNi metal binder as the target, that is, the atomic ratio is 1:1:1:1.

[0072] The matrix was manufactured according to conventional methods, including mixing, grinding, spray drying, pressing and sintering. A cutting tool with a blade geometry of CNMG120408-PM was formed.

[0073] During sintering, a cubic carbide-free zone of approximately 20 μm is formed in the surface region of the base body.

[0074] Coating cutting tools with CVD coating process to deposit TiN / TiCN / α-Al 2 O 3 / TiN layer. The total coating thickness is about 14 μm. The total thickness of the lower TiN and TiCN is about 9 μm.

[0075] Table 1. Matrix composition

[0076]

[0077] The total carbon content was measured by chemical analysis using a LECO WC-600 instrument.

[0078] Table 2. Matrix analysis

[0079]

[0080] The coated cutting tool was subjected to shot peening at 500°C (Invention 1).

[0081] The shot peening of the samples was carried out in an AUER Manual Blasting Cabinet ST 700PS. The blasting medium used was a spherical ceramic bead with an average diameter of about 100 μm. B120. The grain size of the ceramic beads is 63 μm to 125 μm. The composition of the ceramic beads is 60% to 70% ZrO 2 , 28%~33%SiO 2 and <10%Al 2 O 3 The gun pressure was set to 5 bar, the working time was set to 20 seconds, the nozzle diameter was 8 mm, and the projection distance was 100 mm. The shot peening was applied perpendicular to the rake face of the cutting tool. In the case of heated shot peening, the cutting tool was heated with an induction coil heater before shot peening, and the temperature of the cutting tool was measured with a temperature sensor. The induction heater was a Rimac induction heater, 1.5 kW.

[0082] Furthermore, a coated cutting tool according to the above was prepared which was only shot blasted (ie, not shot peened) and is referred to as Reference 1 hereinafter.

[0083] After these post-treatments, the cutting edge of the cutting tool was about ER 40 μm.

[0084] Vickers measurement

[0085] Vickers indentations are formed on the rake face of the cutting tool and on the cross section of the cutting tool. Vickers indentations may also be formed on the flank face.

[0086] The coated samples were polished using standard methods to expose the TiCN layer on the rake face of the cutting tool.Bulk samples were prepared by cutting the insert perpendicular to the rake face using a diamond wheel, followed by polishing using 9 μm diamonds dispersed in oil on paper and then 1 μm diamonds dispersed in oil.

[0087] The Vickers hardness of the polished samples was measured using a programmable hardness tester KB30S from KB Prüftechnik. The measurements were calibrated against HV100 using a test block issued by the Euro Products Calibration Laboratory, UK. The Vickers hardness was measured according to ISO EN6507.

[0088] Vickers hardness measurements are made by programming the hardness tester to make an indentation at a specific location. The indentation is then made using a specified load. At least two parallel HV100 indentations are made, at least 1.5 mm apart from each other, and the results given are average values.

[0089] The crack length at each corner of the Vickers indentation was analyzed and measured with a camera and computer in an Olympus BX51M optical microscope. The specimen and camera were oriented so that the diagonal lines of the Vickers indentation were horizontal and vertical on the computer screen. A magnification of at least 100 times was used. If it was difficult to find the tip of the crack, a higher magnification was applied to locate the tip of the crack before measurement. The two diagonals of each indentation were measured, and the crack was measured as the projection from the corresponding indentation corner to the crack tip on the extended diagonal line of the indentation.

[0090] Residual stress measurement

[0091] Using X-ray diffraction, the so-called sin 2 The ψ method determines the residual stress in the above samples. In this method, the change in the lattice spacing d (and therefore the strain) is measured as a function of the sample tilt angle ψ. The residual stress is given by the strain vs. sin2 The linear slope of the ψ curve is obtained. The residual stress is converted from the strain value by using the X-ray elastic constants.

[0092] XRD measurements were performed on a Bruker Discover D8 diffractometer with Davinci design equipped with a 1 μS microfocus source (CuK α radiation, ), Area detector and 1 / 4 Eulerian bracket. The (2 1 1) reflection of WC at 117.32° 2θ is used for strain measurement. Residual stress measurements are performed in 1 to 4 angular directions, 0°, 90°, 180°, 270°, and for each Direction, 10 equally spaced ψ angles (0° to 50°) were measured for 400 seconds. A collimator with a diameter of 1.0 mm was used in all measurements.

[0093] The resulting residual stress was obtained from the strain data using the X-ray elastic constants of the WC Bragg peak (2 1 1). The X-ray elastic constants were calculated from Poisson's ratio v = 0.191 and Young's modulus = 717.360 GPa.

[0094] Mount the sample to the sample holder using tape.

[0095] The XRD data were analyzed using the software DIFFRAC EVA (Bruker) and High Score Plus (Malvern Panalytical). In the residual stress analysis the software LEPTOS 7 (Bruker) was used.

[0096] Table 3

[0097]

[0098] Table 4

[0099]

[0100] Although the present invention has been described in conjunction with various exemplary embodiments, it should be understood that the present invention is not limited to the disclosed exemplary embodiments; on the contrary, it is intended to cover various modifications and equivalent arrangements within the appended claims. In addition, it should be recognized that any disclosed form or embodiment of the present invention may be combined with any other disclosed or described or suggested form or embodiment as a general matter of design choice. Therefore, the present invention is limited only as indicated by the scope of the appended claims.

Claims

1. A cutting tool comprising a substrate of cemented carbide, wherein said cemented carbide comprises hard constituents in a metallic binder, wherein said hard constituents comprise WC, and wherein the WC content in said cemented carbide is 80 wt% to 95 wt%, and wherein said cemented carbide has an Fe+Ni+Co+Cr content of 3 wt% to 13 wt%, and an atomic ratio of 0.05 < Fe / (Fe+Ni+Co+Cr) < 0.35 and an atomic ratio of 0.05 < Ni / (Fe+Ni+Co+Cr) < 0.35 and an atomic ratio of 0.05 < Co / (Fe+Ni+Co+Cr) < 0.35 and an atomic ratio of 0.05 < Cr / (Fe+Ni+Co+Cr) < 0.35, said cutting tool comprising a rake face, a flank face and a cutting edge therebetween, and wherein the fracture resistance W is defined as where P is the load of the Vickers hardness indentation 100*9.81N, and ā is the average crack length of each crack formed at the corner of the Vickers hardness indentation, and wherein W measured on the rake face of the cutting tool is at least 25% higher than W measured on the cross-section of the body region of the cutting tool.

2. The cutting tool according to claim 1, wherein the compressive residual stress measured in the surface area on the rake face of the cutting tool is >2200 MPa, wherein the stress measurement is performed using X-ray diffraction and sin 2 The ψ method is performed using the (2 11) reflection of WC.

3. The cutting tool according to any one of claims 1 to 2, wherein the crack resistance W measured on the rake face is W 前刀面 The crack resistance W measured on the back face is W 后刀面 The relationship between 前刀面 / W 后刀面 >1.

10.

4. The cutting tool according to any one of claims 1 to 2, wherein the hardness at the surface of the cutting tool > 1500 HV100.

5. The cutting tool according to any one of claims 1 to 2, wherein said cemented carbide has an atomic ratio of 0.2 < Fe / (Fe+Ni+Co+Cr) < 0.3 and an atomic ratio of 0.2 < Ni / (Fe+Ni+Co+Cr) < 0.3 and an atomic ratio of 0.2 < Co / (Fe+Ni+Co+Cr) < 0.3 and an atomic ratio of 0.2 < Cr / (Fe+Ni+Co+Cr) < 0.

3.

6. The cutting tool according to any one of claims 1 to 2, wherein the average WC grain size is 0.2 μm to 10 μm.

7. The cutting tool according to any one of claims 1 to 2, wherein said cemented carbide further comprises one or more of Cu, W, Mo, Mn, Al, Si, Ta, Nb, Ti, Zr, Hf, V.

8. The cutting tool according to any one of claims 1 to 2, wherein the substrate of said cemented carbide comprises a cubic phase, and wherein the substrate of said cemented carbide is provided with a surface region depleted in said cubic phase, and a surface region depleted in said cubic phase means that said surface region does not contain or contains less than 0.5 area% of said cubic phase, and the thickness of said surface region is 2 μm to 100 μm.

9. The cutting tool according to any one of claims 1 to 2, wherein the substrate of said cemented carbide is provided with a coating.

10. The cutting tool according to claim 9, wherein said coating is a coating comprising one or more layers selected from TiN, TiCN, TiC, TiAlN, Al2O3 and ZrCN.

11. The cutting tool according to claim 9, wherein said coating is a coating having a thickness of 2 μm to 20 μm.

12. The cutting tool according to any one of claims 1 to 2, wherein the hardness in the surface area of the cutting tool is the same as the hardness in the body area, with a deviation within 10%.

13. The cutting tool according to any one of claims 1 to 2, wherein the cutting edge radius ER of at least a part of the cutting edge is between 10 μm and 50 μm.

14. A method of manufacturing the cutting tool according to claim 1, comprising: A method of treating a cutting tool comprising a cemented carbide substrate, wherein the cemented carbide comprises hard constituents in a metallic binder, wherein the hard constituents comprise WC, and wherein the WC content in the cemented carbide is 80 wt% to 95 wt%, and wherein the cemented carbide has an Fe + Ni + Co + Cr content of 3 wt% to 13 wt% and an atomic ratio of 0.05 < Fe / (Fe + Ni + Co + Cr) < 0.35 and an atomic ratio of 0.05 < Ni / (Fe + Ni + Co + Cr) < 0.35 and an atomic ratio of 0.05 < Co / (Fe + Ni + Co + Cr) < 0.35 and an atomic ratio of 0.05 < Cr / (Fe + Ni + Co + Cr) < 0.35, and wherein the cutting tool (1) is subjected to shot peening at a temperature equal to or higher than 100 °C.

15. The method according to claim 14, wherein the cutting tool (1) comprises a rake face (2), a flank face (3) and a cutting edge therebetween, and wherein the shot peening is carried out at least on the rake face (2).

16. The method according to any one of claims 14 to 15, wherein the shot peening is carried out on a heated cutting tool, and the method comprises a step of heating the cutting tool before the shot peening.

17. The method according to any one of claims 14 to 15, wherein the method further comprises a step of shot blasting at least a part of the cutting tool, and wherein the step of shot blasting is carried out after the shot peening.

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