Cutting tool and method for producing a cutting tool

Abstract

Cutting tool comprising a hard metal body (10) with a chip surface (14) and a flank surface (12) which intersects with the chip surface (14) to form a cutting edge (16), wherein the hard metal body (10) consists of: a tungsten carbide phase with a grain size distribution in the range of 1 µm to 12 µm; a co-binder phase in a proportion of 9 to 12 mass percent; a solid solution phase of carbides of zirconium and niobium (Zr,Nb)C; and cubic carbides in an amount ranging from 2% to 5% by volume; wherein the solid solution phase of (Zr,Nb)C is the only solid solution phase of the hard metal body (10); wherein niobium is present in a proportion of 0.8 to 1 mass percent and zirconium is present in a proportion of 0.5 to 0.7 mass percent in the hard metal body (10); where the cubic carbides consist of the carbides of the (Zr,Nb)C solid solution phase; wherein the hard metal body (10) has a coercive force (Hcs) in the range of 130 Oe to 150 Oe; wherein the hard metal body (10) has a hardness in the range of 1280 to 1380 HV30; wherein the hard metal body (10) has a density of 14.1 g / cm 3 up to 14.4 g / cm 3 has; wherein the hard metal body (10) does not comprise a binder-enriched zone; and wherein the hard metal body (10) has a mass ratio Nb / (Nb+Zr) ≥ 0.6 and wherein the hard metal body (10) has a multi-layer coating consisting of a TiCN layer adjacent to the hard metal body (10) followed by an outer layer of aluminum oxide (Al2O3), wherein the multi-layer coating was subjected to sandblasting after coating.

Description

[0001] The present invention relates to cutting tools comprising a hard metal body and to methods for producing a cutting tool comprising a hard metal body.

[0002] Cutting tools comprising cemented carbide bodies are used, both coated and uncoated, for machining various metals and alloys. An area of ​​intensive research and development continues to be the improvement of cutting tool resistance to wear and failure modes, including thermal deformation, fracture, and chipping. Considerable resources have been devoted to the development of wear- and refractory coatings for cutting tools. For example, TiC, TiCN, TiOCN, TiN, and Al2O3 have been deposited onto cemented carbides using chemical vapor deposition (CVD) and physical vapor deposition (PVD).

[0003] In addition, the properties of the underlying cutting tool substrate have been investigated. Cutting tool manufacturers have studied compositional changes in cemented carbide bodies and the resulting effects on cemented carbide properties, including hardness, wear resistance, thermal deformation resistance, toughness, density, and various magnetic properties. However, the improvement of one cemented carbide property is often accompanied by the deterioration of another. For example, increasing the deformation resistance of a cemented carbide body can lead to reduced toughness and thermal conductivity of the body. Japanese Patent Application Publication JP 2002-356734 A recognizes such a problem and describes a cemented carbide body with resistance to plastic deformation and increased hardness and thermal conductivity.According to JP 2002-356 734 A, these objectives are achieved by incorporating several different solid solution phases of carbides, nitrides and carbonitrides of metals from groups IVB, VB and VIB into the cemented carbide body.

[0004] US 2003 / 0 129 456 A1 describes a cemented carbide comprising a hard phase component comprising a tungsten carbide and at least one substance selected from carbides, nitrides and carbonitrides of the metals of groups 4a, 5a and 6a of the Periodic Table and a binder phase component comprising at least one of the metals of the iron group, wherein the surface area of ​​the cemented carbide has 90 to 98% of the minimum hardness compared to the internal hardness.

[0005] DE 103 56 470 A1 discloses a cemented carbide body comprising tungsten carbide, a binder phase comprising at least one metal of the iron group or an alloy thereof, and one or more solid-solution phases, each of which comprises at least one of the carbides and carbonitrides of, in combination, zirconium, niobium, and tungsten.

[0006] Nevertheless, improvements in cemented carbide substrates are needed to meet the increasing demands of metalworking applications, and compositional changes in cemented carbide bodies in attempts to provide cutting tools with improved performance require a careful balance between competing properties.

[0007] The object is achieved by a cutting tool comprising a hard metal body according to claim 1 and a method for producing a cutting tool comprising a hard metal body according to claim 3.

[0008] In one aspect, cutting tools having a cemented carbide body are described herein, which, in some embodiments, may exhibit improved resistance to wear and / or one or more failure modes. For example, in some embodiments, a cemented carbide body described herein exhibits increased resistance to thermal deformation without significant loss of toughness.

[0009] A cemented carbide body described herein comprises a tungsten carbide phase, a Co binder phase, a solid solution phase of carbides of zirconium and niobium (Zr,Nb)C, and cubic carbides in an amount ranging from 2 volume percent to 5 volume percent. Furthermore, the cubic carbides of the cemented carbide body consist of the zirconium and niobium carbides of the solid solution phase.

[0010] A cemented carbide body described herein further comprises a coating deposited thereon by physical vapor deposition (PVD), chemical vapor deposition (CVD), or a combination thereof. Groups of the periodic table described herein are identified according to their CAS designation. The coating is a multilayer coating.

[0011] A cemented carbide body described herein is in the form of a cutting tool for one or more metalworking applications. The cemented carbide body includes a rake face and a flank face that intersects with the rake face to form a cutting edge.

[0012] In another aspect, methods for producing cutting tools with cemented carbide bodies are described herein. According to the invention, the method for producing a cemented carbide body comprises providing a mixture consisting of a tungsten carbide powder, cobalt binder powder, and a powdered solid solution carbide of zirconium and niobium (Zr,Nb)C. A green compact is formed from the mixture and sintered to provide the cemented carbide body comprising a tungsten carbide phase, a binder phase, a solid solution phase of (Zr,Nb)C, and cubic carbides in an amount ranging from 2 volume percent to 5 volume percent, wherein the cemented carbide body has a coercive force in the range of 130 Oe to 150 Oe, and wherein the body does not comprise a binder-enriched zone.

[0013] These and other embodiments are described in more detail in the following detailed description. Fig.1 illustrates a cemented carbide body in the form of a cutting tool according to an embodiment described herein. Fig. 2 illustrates results of deformation tests of a cemented carbide body according to an embodiment described herein with respect to comparative cemented carbide bodies. Fig. 3 illustrates toughness test results of a cemented carbide body according to an embodiment described herein with respect to comparative cemented carbide bodies. Fig. 4 illustrates results of interrupted cut cutting tests of a cemented carbide body according to an embodiment described herein with respect to comparative cemented carbide bodies. Fig. 5 illustrates results of interrupted cut cutting tests of a cemented carbide body according to an embodiment described herein with respect to comparative cemented carbide bodies. Fig.6 illustrates results of milling tests of a cemented carbide body according to an embodiment described herein with respect to a comparative cemented carbide body.

[0014] Embodiments described herein will be more readily understood by reference to the following detailed description and the following examples, and their preceding and subsequent descriptions. However, elements, apparatus, and methods described herein are not limited to the specific embodiments set forth in the detailed description and examples. It is to be understood that these embodiments are merely illustrative of the principles of the present invention. Numerous modifications and adaptations will readily occur to those skilled in the art without departing from the scope of the claims.

[0015] In one aspect, cemented carbide bodies are described herein that, in some embodiments, may exhibit improved resistance to wear and / or one or more failure modes. For example, in some embodiments, a cemented carbide body described herein exhibits increased resistance to thermal deformation without significant loss of toughness.

[0016] A cemented carbide body described herein comprises a tungsten carbide phase, a Co binder phase, a solid solution phase of carbides of zirconium and niobium (Zr,Nb)C, and cubic carbides in an amount ranging from 2 volume percent to 5 volume percent.

[0017] Regarding the components of a cemented carbide body, a cemented carbide body described herein comprises a solid solution phase of carbides of zirconium and niobium (Zr,Nb)C. Because the solid solution phase is formed from carbides of zirconium and niobium, it does not comprise any additional metallic elements beyond trace or impurity amounts. Furthermore, the solid solution phase of (Zr,Nb)C is the only solid solution phase of the cemented carbide body. Therefore, a cemented carbide body described herein does not comprise any additional solid solution phases of carbides, nitrides, and / or carbonitrides of metals from Groups IVB, VB, and VIB of the Periodic Table. For example, a cemented carbide body described herein does not contain a solid solution phase comprising a carbide, nitride, and / or carbonitride of titanium, hafnium, vanadium, tantalum, tungsten, molybdenum, or chromium, or mixtures thereof.

[0018] According to the invention, niobium is present in a cemented carbide body described herein in an amount ranging from 0.8 mass percent to 1 mass percent. Additionally, zirconium is present in the cemented carbide body in an amount ranging from 0.5 mass percent to 0.7 mass percent. According to the invention, a cemented carbide body has a mass ratio of Nb / (Nb+Zr) greater than or equal to 0.6. In some embodiments, the mass ratio is greater than or equal to 0.7.

[0019] A cemented carbide body described herein also includes cubic carbides in an amount ranging from 2 volume percent to 5 volume percent. In some embodiments, cubic carbides are present in an amount ranging from 2.5 volume percent to 4 volume percent.

[0020] According to the invention, cubic carbides of the cemented carbide body consist of the carbides of niobium and zirconium of the solid solution phase (Zr,Nb)C. Therefore, cubic carbides of the cemented carbide body do not contain any additional metals from Groups IVB, VB, and VIB of the Periodic Table beyond trace or impurity amounts. For example, cubic carbides of the cemented carbide body do not contain titanium, tantalum, or mixtures thereof in more than trace or impurity amounts.

[0021] A cemented carbide body described herein also comprises a tungsten carbide (WC) phase. The particles of the tungsten carbide phase exhibit a grain size distribution in the range of 1 µm to 12 µm. In some embodiments, the particles of the tungsten carbide phase exhibit a particle size distribution in the range of 2 µm to 10 µm.

[0022] Furthermore, the binder phase of a cemented carbide body described herein comprises cobalt. Additional alloying elements, such as chromium and / or tungsten, may be present in the binder phase. The binder phase is present in the cemented carbide body in an amount ranging from 9 to 12 percent by mass.

[0023] According to the invention, a cemented carbide body described herein does not comprise a binder-enriched zone, including, among other things, a binder-enriched surface zone. For example, in some embodiments, a cemented carbide body does not comprise a binder-enriched surface zone that is free or substantially free of cubic carbides and / or the (Zr, Nb)C solid solution phase.

[0024] A cemented carbide body described herein further comprises a coating deposited thereon by physical vapor deposition (PVD), chemical vapor deposition (CVD), or a combination thereof. The coating is a multilayer coating. The multilayer coating consists of a TiCN layer adjacent to the cemented carbide body followed by an outer layer of aluminum oxide (Al2O3). In some embodiments, the TiCN layer is a medium-temperature TiCN (MT-TiCN) layer, while the aluminum oxide layer is an α-alumina layer, κ-alumina layer, or a mixture thereof. The multilayer coating has been subjected to one or more post-treatment processes such as gritblasting after coating.In some embodiments, a sandblasting treatment is administered in accordance with the disclosure of US 6,869,334 B1, which is hereby expressly incorporated by reference in its entirety.

[0025] A cemented carbide body described herein has a hardness (HV30) in the range of 1280 to 1380 HV30. Vickers hardness values ​​stated herein are determined according to ASTM E 384, "Standard Method for Knoop and Vickers Hardness of Materials," ASTM International.

[0026] Furthermore, according to the invention, a cemented carbide body described herein has a coercivity in the range of 130 Oe to 150 Oe. In some embodiments, a cemented carbide body has a coercivity in the range of 135 Oe to 150 Oe. Coercivity values ​​stated herein are determined according to ASTM B887, "Standard Test Method for Determination of Coercivity (Hcs) of Cemented Carbides," ASTM International.

[0027] In some embodiments, a cemented carbide body described herein has a magnetic saturation (Ms) in the range of 75% to 95%. In some embodiments, a cemented carbide body has a magnetic saturation in the range of 79% to 89%. In some embodiments, a cemented carbide body has a magnetic saturation in the range of 80% to 85%. Magnetic saturation values ​​reported herein are determined according to ASTM B 886, “Standard Test Method for Determination of Magnetic Saturation (Ms) of Cemented Carbides,” ASTM International. As is known to those skilled in the art, magnetic saturation values ​​can be determined based on a comparison to a nominally pure Co binder phase of percentages in µTm -3 / kg. See, for example, Roebuck, B. Magnetic Moment (Saturation) Measurements on Hardmetals, Int. J. Refractory Metals & Hard Materials, 14 (1996) 419-424.

[0028] In addition, a cemented carbide body described herein has a density in the range of 14.1 g / cm 3 up to 14.4 g / cm 3 .

[0029] A cemented carbide body described herein may have any combination of the above properties. For example, a cemented carbide body may comprise any of the above-specified values ​​for hardness, coercivity, magnetic saturation, and density.

[0030] The carbide body is shaped like a cutting tool. The carbide body comprises a rake face and a flank face that intersects with the rake face to form a cutting edge. Fig. 1 illustrates a hard metal body in the form of a cutting tool according to an embodiment described herein. As in Fig.As illustrated in Figure 1, the carbide body (10) comprises a flank surface (12) and a rake surface (14), wherein the flank surface (12) and the rake surface (14) intersect to provide a cutting edge (16). The carbide body (10) also comprises an opening (18) by means of which the body (10) can be attached to a tool holder.

[0031] In another aspect, methods for producing cutting tools with cemented carbide bodies are described herein. The method for producing a cemented carbide body comprises providing a mixture consisting of a tungsten carbide powder, binder powder comprising cobalt powder, and a powdered solid solution carbide of zirconium and niobium (Zr,Nb)C. A green compact is formed from the mixture and sintered to provide the cemented carbide body comprising a tungsten carbide phase, a binder phase, a solid solution phase of (Zr,Nb)C, and cubic carbides in an amount ranging from 0.5 volume percent to 6 volume percent. The tungsten carbide phase, the binder phase, the solid solution phase of (Zr,Nb)C, and the cubic carbides may have any of the properties specified above for such phases.For example, the solid solution phase of (Zr,Nb)C is the only solid solution phase of the cemented carbide body described here. Furthermore, the cubic carbides consist of the niobium and zirconium carbides of the solid solution phase.

[0032] In some embodiments of the methods described herein, metals are provided to the powdered mixture in amounts corresponding to their desired compositional percentages of the cemented carbide body. For example, in some embodiments, the binder powder comprising cobalt powder is provided to the mixture in an amount ranging from 9 mass percent to 12 mass percent.

[0033] Furthermore, in processes according to the invention, solid solution powder of carbides of niobium and zirconium (Zr,Nb)C is added to the mixture in an amount sufficient to provide a niobium content in the range of 0.8 mass percent to 1 mass percent and a zirconium content in the range of 0.5 mass percent to 0.7 mass percent. A (Zr,Nb)C solid solution powder for use in the process described herein has a mass ratio Nb / (Nb+Zr) greater than or equal to 0.6. In some embodiments, the mass ratio is greater than or equal to 0.7.

[0034] Tungsten carbide powder serves as the remainder of the mixture used to form cemented carbide bodies described herein.

[0035] The green compact may be sintered to provide a cemented carbide body described herein under any conditions not inconsistent with the objectives of the present invention. In some embodiments, for example, the green compact is vacuum sintered or sintered and hot isostatically pressed (HIP) at a temperature in the range of 1400°C to 1560°C. In some embodiments, the green compact is sintered for a time in the range of 15 minutes to 120 minutes. In some embodiments, the green compact is sintered for a time in the range of 15 minutes to 90 minutes or 30 minutes to 75 minutes.

[0036] In a process for producing a cemented carbide body, a coating is deposited on the cemented carbide body using PVD, CVD, or a combination thereof. The coating is a multilayer coating.

[0037] In another aspect, methods of cutting metal are described herein. In some embodiments, a method of cutting metal comprises providing a metal workpiece and cutting the metal workpiece with a cutting tool, the cutting tool comprising a cemented carbide body consisting of a tungsten carbide phase, a Co binder phase, a solid solution phase of carbides of zirconium and niobium (Zr,Nb)C, and cubic carbides in an amount ranging from 2 volume percent to 5 volume percent. In some embodiments of methods of cutting metal, the cemented carbide body can have any of the properties described herein for a cemented carbide body. In addition, the cemented carbide body further comprises a coating as described herein.

[0038] In some embodiments, the metal workpiece comprises unalloyed and alloyed steel, stainless steel, gray cast iron, gray ductile cast iron, and various high temperature alloys.

[0039] These and other embodiments are further illustrated by the following non-limiting examples. EXAMPLE 1Carbide body

[0040] Powder mixture (A) according to an embodiment described herein, having the metal composition parameters specified in Table I, was pressed into a green compact with the ANSI standard geometry CNMG120408 RP. As specified in Table I, (ZrNb)C solid solution powder was added to the mixture in an amount sufficient to provide a niobium content of 0.93 mass percent and a zirconium content of 0.62 mass percent. After the addition of 10.6 mass percent cobalt, tungsten carbide (WC) powder formed the remainder of the mixture. The green compact was vacuum sintered at a temperature in the range of 1400°C–1560°C for a period of 30–60 minutes to provide a cemented carbide body. Table I - Powder mixture of hard metal body (mass percent) Example Cobalt chrome Tantalum (TaC) Niobium / Zirconium* Tungsten (WC) A 10,6 - - 0,93 / 0,62 rest * As (ZrNb)C solid solution with mass ratio Nb / (Nb+Zr) ≥ 0.6

[0041] Powder mixtures (BE) with the metal composition parameters given in Table II were also pressed into green compacts with the insert geometry CNMG120408 RP and sintered analogously to powder mixture A to provide comparison cemented carbide bodies. Table II - Powder mixtures of comparative cemented carbide bodies (mass percent) Example Cobalt chrome Tantalum (TaC)* Niobium (NbC)* Zirconium (ZrC) Tungsten (WC) B 11,5 0,40 - - - rest C 10,0 0,35 - - - rest D 10,5 - 1,7 0,83 - rest E 10,5 - 1,1 0,27 - rest * Provides a (TaNb)C solid solution powder

[0042] As indicated in Table II, in Examples D and E, (TaNb)C solid solution powder was added to the mixture in an amount sufficient to provide the tantalum and niobium mass percentages. After the addition of 10.5 mass percent cobalt, WC powder formed the remainder of the powder mixture. For Examples B and C, WC powder also formed the remainder of the mixture after the addition of the cobalt and chromium mass percentages.

[0043] The cemented carbide body examples AE were coated by chemical vapor deposition (CVD) with a multilayer coating consisting of a titanium carbonitride (TiCN) inner layer and an α-alumina outer layer. The coating thickness for each example is given in Table III below. The cemented carbide body examples AE were then subjected to the various ASTM test methods specified herein, the results of which are also given in Table III. Table III - Properties of cemented carbide bodies Example Density (g / cm 3 ) Magnetic saturation (0.1 µTm -3 / kg) Coercive force (Oe) Hardness (HV30) Coating thickness (µm) A 14,10 181 143 1331 7,0 B 14,19 191 146 1316 7,7 C 14,33 167 143 1351 7,7 D 14,22 179 147 1321 8,8 E 14,35 181 148 1327 8,3 EXAMPLE 2 Deformation tests

[0044] Cemented carbide bodies produced according to Examples AE of Example 1 were subjected to a deformation turning test under the following conditions: Workpiece - 42CrMo4 (1.7225) Cutting speed - 270, 285, 300, 315 and 330 m / min Cutting time - 5 seconds per cutting speed Feed - 0.3 mm / rev Cutting depth - 2.5 mm Coolant - none Cutting insert holder - MCLNL3225P12

[0045] The average corner wear (mm) of the cemented carbide body examples AE at a cutting speed of 315 m / min over three repetitions is given in Table IV. The cutting speed of 315 m / min was reached after the cemented carbide body examples AE had undergone cutting speeds of 270, 285, and 300 m / min. In some cases, a cemented carbide cutting tool reached end of tool life (EDS) before or during the application of the cutting speed of 315 m / min. EDS was determined by plastic deformation due to thermal overload, which was indicated by corner wear ≥ 0.6 mm and / or coating flaking. Table IV - Average corner wear (mm) at a cutting speed of 315 m / min Example WIED1 WIED2 WIED3 Average A 0,295 0,293 0,364 0,320 B EDS 0,520 EDS >0,5 C 0,438 0,361 0,327 0,380 D 0,247 0,347 0,357 0,320 E 0,417 0,360 0,433 0,400

[0046] As indicated in Table IV, the cemented carbide body of Example A, having compositional parameters and properties described herein, exhibited the highest corner wear resistance, thereby exceeding Comparative Examples B, C, and E and equaling the performance of Comparative Example D.

[0047] Furthermore, the cemented carbide body of Example A showed desirable resistance to thermal deformation with respect to the comparative examples. As shown in Fig. As illustrated in Figure 2, the cemented carbide body of Example A showed significantly less thermal deformation at the cutting speed of 285 m / min compared to Examples B and C. For example, coating flaking was significant for Examples B and C, but virtually nonexistent for Example A. EXAMPLE 3 Toughness tests

[0048] Cemented carbide bodies produced according to Examples AE of Example 1 were subjected to a toughness turning test under the following conditions: Workpiece - CK60 (1.1221) Cutting speed - 100 m / min Feed - 0.4, 0.5, 0.6, 0.7, 0.8 mm / rev Impacts per feed - 100 Cutting depth - 2.5 mm Coolant - none Cutting insert holder - MCLNL3225P12

[0049] The results of the toughness tests of the cemented carbide body examples AE over two repetitions are shown in Fig. 3. The criteria for EDS were carbide body fracture and / or plastic deformation due to thermal overload, which was indicated by corner wear ≥ 0.6 mm and / or coating flaking. As in Fig. As shown in Figure 3, the cemented carbide body of Example A demonstrated toughness comparable to that of Comparative Examples BE. EXAMPLE 4Cutting test with interrupted cut

[0050] Cemented carbide bodies prepared according to Examples AE of Example 1 were subjected to an interrupted cut turning test under the following conditions: Workpiece - 42CrMo4 (1.7225) Cutting speed - 160 m / min Cutting time - Up to 4 minutes or until tool failure Feed - 0.3 mm / rev for 3 minutes, 0.35 mm / rev from 3-4 minutes Cutting depth - 3 mm Coolant - yes Cutting insert holder - MCLNL3225P12

[0051] Fig. Figure 4 illustrates the results of the interrupted cut tests, with the best performance of five repetitions for each of the examples AE. The EDS criteria were corner wear > 0.4 mm and / or plastic deformation due to thermal overload, which was demonstrated by coating flaking associated with corner wear ≥ 0.4 mm. As shown in Fig.As illustrated in Figure 4, the cemented carbide body of Example A showed the highest wear resistance. Fig. Figure 5 further illustrates the improved wear resistance properties of the cemented carbide body of Example A compared to Examples B and C. EXAMPLE 5Milling tests

[0052] The powder mixtures (A) and (BE) specified in Tables I and II of Example 1 were each pressed into a green compact with the ANSI standard geometry SEKN1203AFSN3 and vacuum sintered at a temperature in the range of 1400 °C-1560 °C for a period of 30-60 minutes to provide the cemented carbide body examples AE.

[0053] The cemented carbide body samples AE were coated with a multilayer coating consisting of a TiCN inner layer and an α-aluminum oxide outer layer, with a coating thickness of 9 µm for each sample. The cemented carbide body samples AE were then subjected to a face milling test under the following conditions: Workpiece - 42CrMo4V Cutting speed - 250 m / min Feed per tooth - 0.3 mm Axial cutting depth - 2.0 mm Radial cutting depth - 120 mm Coolant - none Machine - Heller PFH 12-1400 Tool adapter - SK 50

[0054] The average cutting length to EDS of the cemented carbide body examples AE over three repetitions is given in Table V. The EDS criteria were flank wear of more than 0.3 mm and / or plastic deformation due to thermal overload, which was evidenced by coating flaking associated with flank wear of more than 0.3 mm. Table V - Average cutting length (mm) before EDS Example WIED 1 WIED 2 WIED 3 Standard deviation Average A 1009 800 962 110 924 B 118 115 125 5 119 C 365 370 360 5 365 D 669 903 800 117 794 E 790 738 800 33 776

[0055] As indicated in Table V, the cemented carbide bodies of Example A, having compositional parameters described herein, had the longest cutting length and therefore showed improved resistance to thermal deformation without loss of toughness under the above severe milling conditions. Fig.Figure 6 further illustrates the improved performance of the cemented carbide body of Example A compared to the comparative cemented carbide body of Example E. At approximately the same cutting lengths of 800 mm, the cemented carbide body of Example E showed significant rake face coating flaking, crater wear, and deformation compared to the wear of Example A. EXAMPLE 6Milling tests

[0056] The milling test of Example 5 was repeated, with the only variation being a change in cutting speed from 250 m / min to 200 m / min. The test results are presented in Table VI. Table VI - Average cutting length (mm) before EDS Example WIED 1 WIED 2 WIED 3 Standard deviation Average A 4000 4000 4800 462 4267 B 932 485 400 286 606 C 1600 2800 2000 611 2133 D 2800 2800 4400 924 3333 E 2800 2800 4000 693 3200

[0057] As indicated in Table VI, the cemented carbide bodies of Example A, having compositional parameters described herein, had the longest cutting length and therefore showed improved resistance to thermal deformation without loss of toughness under the above severe milling conditions.

[0058] Various embodiments of the invention have been described in fulfillment of the various objects of the invention. It should be understood that these embodiments are merely illustrative of the principles of the present invention. Numerous modifications and adaptations will readily occur to those skilled in the art without departing from the scope of the following claims.

Claims

[1] Cutting tool comprising a hard metal body (10) with a chip surface (14) and a flank surface (12) which intersects with the chip surface (14) to form a cutting edge (16), the hard metal body (10) consisting of: a tungsten carbide phase with a grain size distribution in the range of 1 µm to 12 µm; a co-binder phase in a proportion of 9 to 12 mass percent; a solid solution phase of carbides of zirconium and niobium (Zr,Nb)C; and cubic carbides in an amount ranging from 2% to 5% by volume; wherein the solid solution phase of (Zr,Nb)C is the only solid solution phase of the hard metal body (10); wherein niobium is present in a proportion of 0.8 to 1 mass percent and zirconium is present in a proportion of 0.5 to 0.7 mass percent in the hard metal body (10); where the cubic carbides consist of the carbides of the (Zr,Nb)C solid solution phase; wherein the hard metal body (10) has a coercive force (Hcs) in the range of 130 Oe to 150 Oe; wherein the hard metal body (10) has a hardness in the range of 1280 to 1380 HV30; wherein the hard metal body (10) has a density of 14.1 g / cm 3 up to 14.4 g / cm 3 has; wherein the hard metal body (10) does not comprise a binder-enriched zone; and wherein the hard metal body (10) has a mass ratio Nb / (Nb+Zr) ≥ 0.6 and wherein the hard metal body (10) has a multi-layer coating consisting of a TiCN layer adjacent to the hard metal body (10) followed by an outer layer of aluminum oxide (Al2O3), wherein the multi-layer coating was subjected to sandblasting after coating. [2] Cutting tool according to claim 1 with a mass ratio Nb / (Nb+Zr) ≥ 0.

7. [3] A method for producing a cutting tool comprising a hard metal body (10) according to claim 1, comprising: providing a mixture consisting of tungsten carbide powder, cobalt binder powder and a powdered solid solution carbide of zirconium and niobium (Zr,Nb)C; forms a green pellet from the mixture and sintering the green compact to provide the hard metal body, which comprises a tungsten carbide phase, a Co binder phase and a solid solution phase of cubic carbides of (Zr,Nb)C in an amount in the range of 2 volume percent to 5 volume percent, wherein the hard metal body has a coercive force in the range of 130 Oe to 150 Oe. [4] A method according to claim 3, wherein the sintering comprises vacuum sintering or sintering and hot isostatic pressing (HIP). [5] A method according to claim 3 or 4, wherein the powdered solid solution carbide has a mass ratio Nb / (Nb+Zr) ≥ 0.

7. [6] A process according to any one of claims 3 to 5, wherein the green compact is sintered at a temperature in the range of 1400°C to 1560°C.

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