Cutting Tools

Abstract

The present invention relates to a cutting tool comprising a cemented carbide substrate, wherein the cemented carbide contains a hard component in a metal binder. The hard component contains WC, and the WC content in the cemented carbide is 80 to 95% by weight. The cemented carbide has an Fe+Ni+Co+Cr content of 3 to 13% by weight, an atomic ratio of 0.05 < Fe / (Fe+Ni+Co+Cr) < 0.35, an atomic ratio of 0.05 < Ni / (Fe+Ni+Co+Cr) < 0.35, 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 crack resistance W is defined as the division of the load of the Vickers indentation 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 bulk region of the cutting tool.

Description

[Technical field]

[0001] The present invention relates to a cutting tool of a cemented carbide, the cemented carbide comprising a metal binder and a hard constituent comprising WC, the surface region of the cutting tool being more crack resistant than the bulk region of the tool. [Background technology]

[0002] Cutting tools for metal cutting applications typically include a substrate of cemented carbide. Cemented carbide is a material that exhibits both high hardness and toughness, and has been successfully used in cutting applications for decades. To further improve the performance of cutting tools, it is known to coat the tools with wear-resistant coatings. It is also known to treat cutting tools with a process known as post-treatment, which may include steps such as wet blasting, dry blasting, edge brushing and / or polishing. These post-treatment processes typically alter the surface roughness of the cutting tool and / or the residual stresses in the surface regions of the cutting tool.

[0003] The effect of shot peening on cemented carbide has been described by 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. It has been shown that compressive residual stresses are induced in the surface layers of both Co and WC.

[0004] There is a continuing need to improve the life and performance of cutting tools to save time in production and reduce the risk of failure due to broken cutting tools. There is also a need to reduce the amount of Co in the cemented carbide and find alternative cemented carbides that can compete with conventional Co-containing cemented carbides in metal cutting performance. Summary of the Invention

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

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

[0007] The present invention relates to a cutting tool comprising a cemented carbide substrate, the cemented carbide containing a hard component in a metal binder, the hard component containing WC, the WC content in the cemented carbide being 80 to 95% by weight, the cemented carbide having an Fe + Ni + Co + Cr content of 3 to 13% by weight, an atomic ratio of 0.05 < Fe / (Fe + Ni + Co + Cr) < 0.35, an atomic ratio of 0.05 < Ni / (Fe + Ni + Co + Cr) < 0.35, 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 including a rake face, a flank face, and a cutting edge therebetween, the crack resistance W being defined as TIFF0007657220000001.tif13170, P is the load of the Vickers hardness indentation at 100 × 9.81 N, TIFF0007657220000002.tif6170 is the average crack length of each crack formed at the corner of the Vickers hardness indentation, and 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 bulk region of the cutting tool, regarding the cutting tool.

[0008] Within the above composition range, the binder obtains a large solution hardening effect, which gives good high hardness with respect to wear resistance and plastic deformation resistance. However, it is necessary to have good metal cutting characteristics and a good combination of toughness and plastic deformation resistance. Usually, for most technical composite materials such as cemented carbides, the improvement of toughness is related to the decrease in hardness. It was surprisingly found that by processing the material within the specific composition range according to the invention, a crack resistance 25% or more higher on the rake face compared to the bulk was achieved. Cracks formed in the cutting tool during metal cutting usually occur on the rake face side of the cutting tool, and these cracks limit the tool life. Therefore, by improving the crack resistance of the rake face, the tool life of the cutting tool in metal cutting applications will be extended.

[0009] In one embodiment of the present invention, the cemented carbide contains x wt% of Ni, y wt% of Fe, z wt% of Co, and v wt% of Cr, and 5 < x + y + z + v < 9. The cemented carbide with a binder content within this range has a good combination of toughness and plastic deformation resistance for cutting tool applications. Depending on the metal cutting application, the amount of binder can be optimized by those skilled in the art.

[0010] 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, > 2000 MPa, preferably > 2200 MPa, more preferably 2400 - 2800 MPa, and the stress measurement is made by the sin 2 Ψ method using X-ray diffraction and the (211) reflection of WC. Compressive residual stress suppresses the formation of cracks. Therefore, by improving the crack resistance of the rake face, the tool life of the cutting tool in metal cutting applications will be extended.

[0011] In one embodiment of the present invention, the relationship between the crack resistance W(rake) measured on the rake face and the crack resistance W(flank) measured on the flank face is W(rake) / W(flank) > 1.10. Cracks formed during metal cutting usually occur on the rake face side of the cutting tool. Therefore, good crack resistance on the rake face side is advantageous for metal cutting applications. Furthermore, if only the rake face is shot-peened and the flank face side is less likely to crack, the cutting tool manufacturing process will be relatively simple.

[0012] In one embodiment of the present invention, the hardness of the surface of the cutting tool is > 1500 HV100, preferably > 1600 HV100. Improved hardness in the surface area of the cutting tool, particularly in the area of the cutting tool that contacts the workpiece during metal cutting applications, is advantageous in terms of increasing the wear resistance of the cemented carbide. Furthermore, a coating applied on the substrate can withstand longer on a harder substrate, thereby improving the life of the cutting tool.

[0013] In one embodiment of the present invention, the cemented carbide has an atomic ratio of 0.2 < Fe / (Fe + Ni + Co + Cr) < 0.3, an atomic ratio of 0.2 < Ni / (Fe + Ni + Co + Cr) < 0.3, 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. In this composition range, the binder obtains almost the maximum solution hardening effect, which gives good high hardness against wear resistance and plastic deformation resistance.

[0014] In one embodiment of the present invention, the WC particle size is uniform throughout the substrate. A non-uniform WC particle size may cause crack initiation points due to differences in the thermo-mechanical properties of different zones.

[0015] In one embodiment of the present invention, the average WC particle size is 0.2 to 10 μm, preferably 0.5 to 3 μm. In this range, the particle size of WC is optimal for cemented carbide for metal cutting inserts. Depending on the metal cutting application, the WC particle size can be optimized by those skilled in the art.

[0016] In one embodiment of the invention, the cemented carbide further comprises one or more of Cu, W, Mo, Mn, Al, Si, which elements provide strengthening of the cemented carbide by solution hardening.

[0017] In one embodiment of the present invention, the cemented carbide further comprises one or more of Ta, Nb, Ti, Zr, Hf, V. These elements tend to form cubic carbides in the cemented carbide. Cutting tools with cubic carbides have improved bulk hot hardness. These elements are also useful for creating such cubic carbide-free gradient zones. Such cubic carbide-free gradient zones are advantageous in that they provide improved resistance to crack growth in the surface region while maintaining good bulk plastic deformation resistance, which is advantageous for some turning inserts.

[0018] In one embodiment of the invention, the cemented carbide substrate comprises a cubic phase, the cemented carbide substrate comprises a surface zone free of said cubic phase, the surface zone having a thickness of 2-100 μm, preferably 3-70 μm, more preferably 8-35 μm.

[0019] In one embodiment of the invention, the cemented carbide substrate is provided with a coating, preferably a coating comprising one or more layers selected from TiN, TiCN, TiC, TiAlN, Al2O3, and ZrCN, more preferably a coating having a thickness of 2-20 μm.

[0020] In one embodiment of the present invention, the hardness in the surface area and the hardness in the bulk area of ​​the cutting tool are the same within a deviation of 10%. A cemented carbide with uniform hardness in the bulk to the surface is economical for mass production. The hard cemented carbide can then be more resistant to the formation of cracks on the surface according to the present invention.

[0021] The present invention relates to a method for treating a cutting tool including a cemented carbide substrate, wherein the cemented carbide contains a hard component in a metal binder, the hard component contains WC, the WC content in the cemented carbide is 80 to 95% by weight, the cemented carbide has an Fe+Ni+Co+Cr content of 3 to 13% by weight, an atomic ratio of 0.05 < Fe / (Fe+Ni+Co+Cr) < 0.35, an atomic ratio of 0.05 < Ni / (Fe+Ni+Co+Cr) < 0.35, 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 the cutting tool (1) is subjected to shot peening at a temperature of 100°C or higher, preferably 200°C or higher, more preferably 200°C to 600°C. The shot peening of the present invention is carried out at a high temperature in one embodiment, and this temperature is defined herein as the temperature during shot peening of the material (a part of the cutting tool) to be shot peened. Some methods, such as induction heating, resistance heating, preheating on a hot surface / oven, laser heating, etc. can be used to generate a high temperature of a part of the cutting tool. The cutting tool can alternatively be heated in a separate step before the shot peening step.

[0022] The temperature is appropriately measured on the substrate by any method suitable for measuring the temperature. Preferably, an infrared temperature measuring device is used.

[0023] A part of the substrate is subjected to shot peening at the said temperature. It has surprisingly been found that when the cutting tool is heated and the cutting tool is treated by shot peening, the crack resistance in the surface area, which is an important property for improving the life of the cutting tool, is improved.

[0024] In one embodiment of the present invention, a cutting tool (1) includes a rake face (2), a flank face (3), and a cutting edge therebetween, and said shot peening is performed at least on the rake face (2). Cracks that occur in cutting tools during metal cutting usually occur on the rake face side of the cutting tool, and these cracks limit the tool life. Therefore, improving the crack resistance of the rake face will increase the tool life of the cutting tool in metal cutting applications.

[0025] 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 surprisingly been found that cutting tools made by this method perform well with this ER.

[0026] In one embodiment of the invention, shot peening is performed with a heated cutting tool and the method includes a pre-shot peening step, where said cutting tool is heated. Heating the cutting tool before shot peening can be advantageous as it typically takes longer to heat than to apply the shot peening.

[0027] In one embodiment of the invention, the method further comprises the step of shot blasting at least a portion of the cutting tool, the step of shot blasting being performed after the shot peening, which is advantageous as the shot blasting imparts compressive stresses to the top of the coating, which in combination with the shot peening is advantageous for tool life.

[0028] Further objects and features of the present invention will become apparent from the following detailed description. [Brief description of the drawings]

[0029] [Figure 1] FIG. 1 is a general view of a cutting tool insert 1, which comprises a rake face 2, a flank face 3 and a cutting edge provided therebetween. [Diagram 2]1 is a general view of a cross section of a cutting edge, the edge radius ER is indicated and furthermore the cutting edge width A is indicated diagrammatically. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] definition "Cemented carbide" is a material that contains hard components dispersed in a continuous metal binder, where the hard components form a skeleton embedded in the continuous metal binder. The hard components primarily contain WC. This type of material combines high toughness from the metal binder with high hardness from the hard components, making it suitable as a substrate material for metal cutting tools.

[0031] "Composition of" or "content in" a cemented carbide means herein the average composition or average content in a cemented carbide substrate. For example, since a cutting tool is at least a few mm in size, a gradient in a surface region, e.g. 15-30 μm from the surface to the bulk of the substrate, with a locally higher metal binder content, does not change the average composition of the cemented carbide substrate of the cutting tool.

[0032] The "metal binder" of a cemented carbide can contain other elements that are dissolved in the metal binder during sintering, such as W and C from WC. Other elements can also be dissolved in the binder depending on what other types of hard constituents are present.

[0033] By "cutting tool" is meant herein a cutting tool for metal cutting applications, for example an insert, an end mill, or a drill. The field of application can be turning, milling, or drilling.

[0034] "ER" is an edge radius value intended to indicate edge sharpness. A higher ER value represents a rougher cutting edge profile, while a lower ER value represents a sharper cutting edge.

[0035] ER is defined herein as the value calculated according to: - Place the cutting tool on a flat surface on its seat or on a corresponding surface of the cutting tool. - Align the first surface along the side of the cutting tool perpendicular to the flat surface, in contact with the edge, for example measuring along the flank 3 of the cutting tool 1. - aligning a second surface parallel to said flat surface and intersecting said first surface at an intersection point, said second surface being measured at a tangent point tangential to an edge, e.g. said second surface is aligned along the rake face 2 of a cutting tool 1.

[0036] The value "ER" is equal to the distance between the intersection of the first and second surfaces and the point of contact between the first surface and the cutting tool proximate the edge, see FIG.

[0037] "Shot blasting" as used herein refers to a process using abrasive particles where material is removed from a treatment surface, typically by abrasion. Shot blasting is well known in the art of cutting tools and is known to introduce residual stresses, for example, in coatings on cutting tools.

[0038] "Shot peening" as used herein means that the surface of a cutting tool is subjected to a medium that contains particles, so-called beads, which are non-abrasive and typically circular. The media can be beads of hard material, e.g. oxide, steel, or cemented carbide.

[0039] The term "bulk" as used herein means the innermost (center) portion of the cutting tool.

[0040] The term "surface region" as used herein means the outer portion of the substrate that is affected by the shot peening process disclosed herein.

[0041] Further embodiments of the invention In one embodiment of the invention, the cemented carbide further comprises a cubic phase, sometimes referred to as gamma 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 cubic phase, in area %, is suitably 2-25%, preferably 3-15%. This can be measured in different ways, but one way is to carry out image analysis of either light optical microscopy images or scanning electron microscopy (SEM) photographs of cross sections of the substrate to calculate the average proportion of gamma phase.

[0042] In one embodiment of the invention, the cemented carbide comprises a cubic phase and a binder phase-rich surface zone free of cubic phase. The thickness of the surface zone is suitably 2-100 μm, preferably 3-70 μm, more preferably 8-35 μm. The thickness is determined by measurements on SEM or LOM images of a cross section of the substrate. These measurements should be made in an area where the substrate surface is reasonably flat, i.e. not close to the edge, at least 0.3 mm from the cutting edge or nose, etc., to obtain a true value. The boundary between the surface zone and the bulk is determined by the presence or absence of a cubic phase, which is usually quite distinct, 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 bulk. "Binder-rich" means in this specification that the content of the binder phase in the surface zone is suitably 1.05-1.65 times, preferably 1.1-1.5 times, the content of the binder phase in the bulk. The binder phase content in the surface zone is suitably measured at a depth half the total thickness / depth of the surface zone. Any measurements made in the bulk should be made in an area that is not too close to the surface zone. This means that any measurements made on the bulk microstructure herein should be made at a depth of at least 200 μm from the surface.

[0043] A surface zone free of cubic phase means herein that the surface zone is free of cubic phase particles or contains very few, i.e. less than 0.5% by area, of cubic phase particles.

[0044] In one embodiment of the invention, the cutting tool is provided with a coating, which may be a color layer or a wear-resistant coating.

[0045] In one embodiment of the present invention, the coating has a thickness of 2 to 20 μm, preferably 5 to 10 μm.

[0046] In one embodiment of the invention, the cutting tool comprises a coating, the thickness of the coating in the area of ​​hardness measurement being between 3 and 12 μm, preferably less than 6 μm.

[0047] In one embodiment of the invention, the coating is a CVD coating or a PVD coating, preferably the coating comprises one or more layers selected from TiN, TiCN, TiC, TiAlN, Al2O3, and ZrCN. Preferably the coating is a CVD coating comprising a TiCN layer and an Al2O3 layer.

[0048] In one embodiment of the invention, the coating is a CVD coating comprising an inner TiCN layer and an outer α-Al2O3 layer.

[0049] In one embodiment of the invention, the cemented carbide substrate is provided with a wear resistant PVD coating, suitably a nitride, oxide, carbide or mixture thereof with one or more of Al, Si and elements selected from groups 4, 5 and 6 of the periodic table.

[0050] In one embodiment of the invention, the cutting tool comprises a rake face, a flank face and a cutting edge therebetween, said shot peening being performed at least on the rake face. Rake face peening is advantageous in that the work material impacts the cutting tool during the cutting operation and therefore the mechanism during peening that affects the substrate is applied at the rake face, which is applied at the relevant area or volume of the substrate. For many cutting tool geometries this means treating several cutting edges simultaneously, so applying shot peening on the rake face is even more advantageous.

[0051] In one embodiment of the present invention, shot peening is performed with ceramic beads, preferably beads comprising ZrO2, SiO2, and Al2O3.

[0052] In one embodiment of the present invention, shot peening is performed with peening media having an average diameter of 70-150 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 delivered from the media to the substrate becomes barely noticeable. The impact or energy from the beads during shot peening should not be too high, as this increases 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, as the technical effect is then not achieved. If the beads are too large, the risk of damaging the cutting edge increases. If the beads are too small, the energy and impact delivered from the media to the substrate becomes barely noticeable. The appropriate size of the beads is related to the material of the beads and is selected by the person skilled in the art.

[0053] In one embodiment of the invention, shot peening is performed with a heated cutting tool and the method includes a step prior to shot peening, where said cutting tool is heated.

[0054] In one embodiment of the invention, the method further comprises the step of shot blasting at least a portion of the cutting tool, preferably the portion including at least a portion of the cutting edge or a region proximate to the cutting edge.

[0055] In one embodiment of the invention, the shot blasting step is performed after the shot peening. Heating during shot peening can reduce some of the positive effects from shot blasting, such as the induction of residual stresses in the coating, and therefore by choosing to perform the shot peening before the shot blasting, both positive effects can be maintained.

[0056] In one embodiment of the invention, shot blasting and shot peening are performed on the same part of the cutting tool, which is advantageous during large scale production, for example, due to more effective loading of the cutting tool.

[0057] In one embodiment of the invention, the peening is performed with the shot direction perpendicular to the surface of the cutting tool. Perpendicular shot peening is advantageous in that the depth of the substrate affected is greatest when the heated shot peening is in this direction.

[0058] In one embodiment of the invention, the cutting tool 1 is an insert, preferably a milling insert or a turning insert.

[0059] The shot peening process according to the present invention may also be combined with other process steps known in the art of making cutting tools, such as, for example, brushing, abrading, wet blasting, dry blasting, etc. EXAMPLES

[0060] In the following, exemplary embodiments of the present invention are disclosed in more detail in comparison with the reference embodiment: A coated cutting tool (insert) was prepared and analyzed. EXAMPLES

[0061] (Sample Preparation) Cemented carbide substrates were prepared from the raw 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 particle size (FSSS) of WC was 4 μm. The elements Co, Cr, Fe, and Ni were mixed in the following order: 0.99 wt% Co, 2.02 wt% Cr3C2, 4.85 wt% Fe 0.4 Ni 0.4 Co 0.2 The amounts of each ingredient were based on the total dry powder weight. The amounts of Co, Ni, Fe, and Cr elements were calculated to target a CoCrFeNi metallic binder, i.e., 1:1:1:1 atomic ratio.

[0062] The substrate was prepared according to a conventional method, including mixing, milling, spray drying, pressing, and sintering. A cutting tool with insert shape CNMG120408-PM was formed.

[0063] During sintering, a cubic carbide-free zone of about 20 μm was formed in the surface zone of the substrate.

[0064] The cutting tool was coated by a CVD coating process to deposit the layers TiN / TiCN / α-Al2O3 / TiN. The total coating thickness was about 14 μm. The total thickness of the lower TiN and TiCN is about 9 μm. TIFF0007657220000003.tif59170

[0065] Total carbon content was determined by chemical analysis using a LECO WC-600 instrument. TIFF0007657220000004.tif38170

[0066] The coated cutting tool was shot peened at 500°C (Invention 1).

[0067] The shot peening of the samples was carried out in an AUER manual blast cabinet ST700PS machine. A blasting medium of ceramic beads with a spherical shape and an average diameter of about 100 μm (medium Microblast® B120) was used. The particle size of the ceramic beads is 63-125 μm. The ceramic beads have a composition of 60-70% ZrO2, 28-33% SiO2, and <10% Al2O3. The shotgun pressure was set at 5 bar, the working time was set at 20 seconds, the nozzle diameter was 8 mm, and the separation distance was 100 mm. The peening was applied perpendicular to the rake face of the cutting tool. In the case of heated shot peening, the cutting tool was heated by an induction coil heater before shot peening, and the temperature of the cutting tool was measured by a temperature sensor. The induction heater was a Rimac induction heater of 1.5 kW.

[0068] In addition, a cutting tool coated as described above was prepared by only shot blasting, i.e., without shot peening, and is hereinafter referred to as Reference 1.

[0069] The cutting edge of the cutting tool after these post-treatments had an ER of about 40 μm.

[0070] Vickers measurement Vickers impressions were made on the rake face of the cutting tool and on the cross section of the cutting tool. Vickers impressions can also be made on the flank side.

[0071] 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 with 9 μm diamonds dispersed in oil on paper, then 1 μm diamonds dispersed in oil.

[0072] The Vickers hardness of the polished samples was measured using a programmable hardness tester (KB30S by KB Pruftechnik). Measurements were calibrated to HV100 using test blocks from the Euro Products Calibration Laboratory (UK). Vickers hardness was measured according to ISO EN6507.

[0073] Vickers hardness measurements were performed by programming the hardness tester to make an indentation at a certain location. An indentation was then made using a specific load. At least two parallel HV100 indentations were made at a distance of at least 1.5 mm apart, and the results shown are average values.

[0074] The crack length at each corner of the Vickers indentation was analyzed and measured with an Olympus BX51M light optical microscope equipped with a camera and computer. The specimen and camera were aligned so that the diagonals of the Vickers indentation were horizontal and vertical on the computer screen. A magnification of at least 100x 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 measuring. The two diagonals of each indentation were measured and the crack was measured as the projection of the extended diagonal of the indentation from each corner of the indentation to the tip of the crack.

[0075] Residual Stress Measurement Using X-ray diffraction, the so-called sin 2 The residual stress of the aforementioned samples was determined by the Ψ method. In this method, the deviation in lattice spacing d (and therefore strain) is measured as a function of the sample tilt angle Ψ. The residual stress is calculated as the function of strain versus sin 2 It is obtained from the linear slope of the Ψ curve. Residual stress is converted from the strain value by using the X-ray elastic constants.

[0076] XRD measurements were performed using an IμS microfocus radiation source (CuK). αMeasurements were performed on a Davinci-designed Bruker DiscoverD8 diffractometer equipped with a 1 / 4 Euler cradle (radiation, λ = 1.5418 Å), a Vantec-500 area detector and a 1 / 4 Euler cradle. The (211) reflection of WC located at 117.32° 2θ was used for the strain measurements. Residual stress measurements were performed in 1-4 angular directions: Φ: 0°, 90°, 180°, 270°, and for each Φ direction, 10 equidistant Ψ angles (0°-50°) were measured with a measurement time of 400 s. A collimator with a diameter of 1.0 mm was used in all measurements.

[0077] The resulting residual stress was obtained from the strain data by using the X-ray elastic constants for WC, Bragg peak (211). The X-ray elastic constants were calculated from the Poisson's ratio ν=0.191 and Young's modulus=717.360 GPa.

[0078] The sample was attached to a sample holder with adhesive tape.

[0079] XRD data were analyzed with the software DIFFRAC EVA (Bruker) and High Score Plus (Malvern Panalytical). The software LEPTOS7 (Bruker) was used for residual stress analysis. TIFF0007657220000005.tif62170TIFF0007657220000006.tif56170

[0080] Although the present invention has been described in connection with various exemplary embodiments, it is understood that the invention is not limited to the disclosed exemplary embodiments, but is intended to encompass various modifications and equivalent arrangements within the scope of the appended claims. Moreover, it should be recognized that any disclosed form or embodiment of the present invention may be incorporated into any other disclosed or described or suggested form or embodiment as a matter of general design choice. Accordingly, the invention is limited only as indicated by the scope of the appended claims attached hereto.

Claims

1. A cutting tool comprising a substrate of cemented carbide, the cemented carbide comprising a hard component in a metal binder, the hard component comprising WC, the WC content in the cemented carbide being 80-95 wt.%, the cemented carbide having an Fe+Ni+Co+Cr content of 3-13 wt.%, the atomic ratio of which is 0.05<Fe / (Fe+Ni+Co+Cr)<0.35, the atomic ratio of which is 0.05<Ni / (Fe+Ni+Co+Cr)<0.35, the atomic ratio of which is 0.05<Co / (Fe+Ni+Co+Cr)<0.35, the atomic ratio of which is 0.05<Cr / (Fe+Ni+Co+Cr)<0.35, the cutting tool comprising a rake face, a flank face and a cutting edge therebetween, the crack resistance W being It is defined as P is the Vickers hardness indentation load 100 x 9.81 N; is the average crack length of each crack formed at the corner of the Vickers hardness indentation, and wherein W measured at the rake face of the cutting tool is at least 25% higher than W measured at a cross section in a bulk area of ​​the cutting tool, both measured in accordance with ISO EN 6507.

2. The compressive residual stress measured in the surface region on the rake face of the cutting tool is >2000 MPa, and the stress measurement is performed using X-ray diffraction and sin 2+ diffraction using the (211) reflection of WC. ２ The cutting tool according to claim 1 , which is made by the Ψ method.

3. 3. The cutting tool according to claim 1, wherein the relationship between the crack resistance measured on the rake face W(rake) and the crack resistance measured on the flank face W(flank) is W(rake) / W(flank)>1.

10.

4. 4. A cutting tool according to any one of claims 1 to 3, wherein the hardness of the surface of the cutting tool is >1500 HV100.

5. 5. The cutting tool according to claim 1, wherein the cemented carbide has atomic ratios of 0.2<Fe / (Fe+Ni+Co+Cr)<0.3, atomic ratios of 0.2<Ni / (Fe+Ni+Co+Cr)<0.3, atomic ratios of 0.2<Co / (Fe+Ni+Co+Cr)<0.3, and atomic ratios of 0.2<Cr / (Fe+Ni+Co+Cr)<0.

3.

6. A cutting tool according to any one of claims 1 to 5, wherein the average WC grain size is between 0.2 and 10 μm.

7. 7. The cutting tool of claim 1, wherein the cemented carbide further comprises one or more of Cu, W, Mo, Mn, Al, Si, Ta, Nb, Ti, Zr, Hf, V.

8. 8. A cutting tool according to any one of the preceding claims, wherein the cemented carbide substrate comprises a cubic phase, the cemented carbide substrate being provided with a surface zone free of said cubic phase, the surface zone having a thickness of 2 to 100 μm.

9. A cutting tool according to any one of claims 1 to 8, wherein the cemented carbide substrate is provided with a coating.

10. 10. The cutting tool of claim 1, wherein the hardness in the surface region and the hardness in the bulk region of the cutting tool are the same within a 10% deviation.

11. A cutting tool according to any one of the preceding claims, wherein the edge radius ER of at least a part of the cutting edge is between 10 μm and 50 μm.

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