HARD METALS AND METHOD FOR PRODUCING THE SAME

Abstract

The invention concerns the field of hardmetal materials and relates to hardmetals such as those which can, for example, be used as cutting material for tools. The object of the present invention is to specify hardmetals which include a novel concept for the structural composition of the hardmetals. The object is attained with hardmetals which are at least made up of hard phases in particle form and metal binder arranged therebetween, wherein a high-entropy hard phase (HEH) is composed of at least four metals (Me) of the 4th and/or 5th and/or 6th subgroup of the PTE in the form of a solid solution of carbides, nitrides, carbonitrides, oxycarbides, and/or oxycarbonitrides of the metals, wherein the respective amounts of the metals in the HEH are essentially equal.

Claims

1. Hardmetals at least made up of hard phases in particle form and metal binder arranged therebetween, wherein a high-entropy hard phase (HEH), the content of which in the hardmetal according to the invention is at least 50 vol %, is composed of at least four metals (Me) of the 4th and/or 5th and/or 6th subgroup of the periodic table of elements (PTE) in the form of a solid solution of carbides, nitrides, carbonitrides, oxycarbides, and/or oxycarbonitrides of the metals, and wherein the respective amount x, y, and z in total of the carbon (C), nitrogen (N), and oxygen (O) in the carbides, nitrides, carbonitrides, oxycarbides, and/or oxycarbonitrides of the metals of the 4th and/or 5th and/or 6th subgroup of the PTE is in accordance with MeC.sub.xN.sub.yO.sub.z=0.7≤x+y+z≤1, and wherein the respective amounts of the metals of the 4th and/or 5th and/or 6th subgroup of the PTE in the at least four metals in the HEH are essentially equal or the amount of one or more of said metals differs therefrom by maximally 20 at. %, and wherein the carbides, nitrides, carbonitrides, oxycarbides, and/or oxycarbonitrides of the metals of the 4th and/or 5th and/or 6th subgroup of the PTE are present in each hard phase particle as a solid solution, and furthermore maximally 50 vol % of the hard phases have a different hard phase composition, and wherein as metal binders all metal binders known for hardmetals are present in the amounts of 0.1 to 40 vol %, in relation to the hardmetal, known for hardmetals.

2. The hardmetals according to claim 1 in which 50-100 vol %, advantageously 60-99 vol %, more advantageously 80-98 vol % of the hard phases are an HEH of at least four metals of the 4th and/or 5th and/or 6th subgroup of the PTE in the form of a solid solution of carbides, nitrides, carbonitrides, oxycarbides, and/or oxycarbonitrides.

3. The hardmetals according to claim 1 in which 0-50 vol %, advantageously 1 to 20 vol %, of additional hard phases in the hardmetal are composed of one, two, or three metals of the 4th and/or 5th and/or 6th subgroup of the periodic table of elements (PTE) in the form of a solid solution of carbides, nitrides, carbonitrides, oxycarbides, and/or oxycarbonitrides of the metals.

4. The hardmetals according to claim 1 in which the hard phases are composed of carbides or nitrides of the metals of the 4th and/or 5th and/or 6th subgroup of the PTE.

5. The hardmetals according to claim 1 in which the respective amount x, y, and z in total of the carbon (C), nitrogen (N), and oxygen (O) in the carbides, nitrides, carbonitrides, oxycarbides, and/or oxycarbonitrides with metals of the 4th and/or 5th and/or 6th subgroup of the PTE is in accordance with MeC.sub.xN.sub.yO.sub.z=0.9≤x+y+z≤1, advantageously with MeC.sub.xN.sub.yO.sub.z where x=0-1 and/or y=0-1 and/or z=0-0.2

6. The hardmetals according to claim 1 in which the amounts of the metals are present according to the following: HEH of a number of n metals of the 4th and/or 5th and/or 6th subgroup of the PTE with n=4 to 9, wherein in the case of n=4 to 6 the amounts of the respective metals can differ according to (1/n.Math.100) ±10 at. %, advantageously ±5 at. %, more advantageously ±2 at. %, and/or in the case of n=7 to 9 the amounts of the respective metals can differ according to (1/n.Math.100) ±5 at. %, advantageously ±2 at. %, and/or the amounts of n−3 (n minus 3) of the metals can also differ by respective amounts of >10 at. %, in relation to the total metal content in the HEH, wherein the amount of one of the metals can maximally be 70 at. %, advantageously 60 at. %, in relation to the total metal content of the HEH.

7. The hardmetals according to claim 1 in which each amount of a metal differs by maximally 20 at. % from the amount which results from the equal amounts for all metals with n metals.

8. The hardmetals according to claim 1 in which the hard phase HEH is present such that it is composed of five, six, seven, or more metals of the 4th and/or 5th and/or 6th subgroup of the PTE in the form of a solid solution of carbides, nitrides, carbonitrides, oxycarbides, and/or oxycarbonitrides.

9. The hardmetals according to claim 1 in which, in the HEH of at least four metals of the 4th and/or 5th and/or 6th subgroup of the PTE in the form of a solid solution of carbides, nitrides, carbonitrides, and/or oxycarbonitrides, the amount of the at least four metals of the 4th and/or 5th and/or 6th subgroup of the PTE in the form of carbides, nitrides, carbonitrides, and/or oxycarbonitrides is each essentially equal.

10. The hardmetals according to claim 1 in which Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W are present as metals of the hard phases.

11. The hardmetals according to claim 1 in which Co, Ni, Fe, Mn, Cu, Cr, Ti or mixtures thereof, such as low-carbon and high-carbon steels and high-entropy metal alloys, are present as metal binders.

12. The hardmetals according to claim 1 in which 5 to 32 vol % metal binder, in relation to the hardmetal, is contained in the hardmetals.

13. A method for producing hardmetals in which powders from at least four metals of the 4th and/or 5th and/or 6th subgroup of the periodic table of elements (PTE) in the form of carbides, nitrides, carbonitrides, and/or oxycarbonitrides are mixed and synthesized into an HEH powder or into HEH granules, and maximally 50 vol % additional hard phase powders or hard phase granules are subsequently added to the HEH powders or the granules of the HEH, and these hard phases are mixed with metal binder in powder form in an amount of 0.1 to 40 vol %, in relation to the hardmetal, and sintered to form hardmetal powder or hardmetal granules and, after a shaping, component parts.

14. The method according to claim 13 in which component parts are formed from the mixture with organic binders via a shaping process, the organic binders are removed, and the component parts are sintered.

15. The method according to claim 13 in which the shaping is realized by means of pressing, extruding, injection molding, CIP (cold isostatic pressing), and/or by means of additive shaping.

16. The method according to claim 13 in which the sintering occurs in a pressure-free or pressure-assisted manner by means of sinter hot isostatic pressing, hot isostatic pressing (HIP), hot pressing, or SPS.

17. The method according to claim 13 in which at least five or six or seven or more powders of metals of the 4th and/or 5th and/or 6th subgroup of the PTE in the form of carbides, nitrides, carbonitrides, and/or oxycarbonitrides are mixed and the mixture is synthesized with metal binders in situ during the sintering to form hardmetals containing HEH.

18. The method according to claim 13 in which four powders of metals of the 4th and/or 5th and/or 6th subgroup of the PTE in the form of carbides and/or nitrides are mixed and the mixture is synthesized with metal binders in situ during the sintering to form hardmetals containing HEH.

19. The method according to claim 13 in which 0-<50 vol %, advantageously 1 to 20 vol %, of powders from hard phases of one or two or three metals of the 4th and/or 5th and/or 6th subgroup of the PTE in the form of a solid solution of carbides, nitrides, carbonitrides, and/or oxycarbonitrides are used.

20. The method according to claim 13 in which the synthesis of the HEH powders is carried out from the reduction of oxides from metals of the 4th and/or 5th and/or 6th subgroup of the PTE into metals and the subsequent Co carburization and/or nitriding or occurs through a direct carburization and/or nitriding of the mixed oxides.

21. The method according to claim 13 in which maximally 50 vol % additional hard phase powders are added to HEH powder, and said hard phases are mixed with metal binder in powder form in an amount of 0.1 to 40 vol %, in relation to the hardmetal, and subsequently sintered to form partially or fully sintered hardmetal granules.

Description

EXAMPLE 1

[0099] A single-phase high-entropy hard phase HEH having the composition (Ta.sub.0.21Nb.sub.0.21Ti.sub.0.21V.sub.0.19W.sub.0.18)C produced from 20 at. % each of TaC, NbC, TiC, VC, and WC by means of a sintering at 1950° C. under vacuum and a subsequent comminution in a ball mill was milled with 14 vol % cobalt (HalfMicron, from UmiCore) in a ball mill in a solvent (heptane) and at a powder/grinding ball ratio of 1:20 for 48 h. Following the drying, bending fracture rods having the geometry 45×5×6 mm.sup.3 were pressed from the powder by means of uniaxial pressing at 200 MPa.

[0100] The samples were sintered at 1280° C. for 45 min in a SinterHIP furnace with an HIP pressure of 10 MPa.

[0101] The sample bodies proved to be completely densified under a light microscope. The porosity according to ISO 4505 corresponded to >A02, B00, C00. The Vickers hardness was determined to be 1620 HV10, and the fracture toughness (K.sub.1C) was calculated to be 8.5 MPa*m.sup.1/2 by means of the measurement of the crack lengths and using the formula from Shetty (Shetty 1985—Indentation fracture of WC—Co cermets).

[0102] Results of these studies for the density, porosity, magnetic saturation, coercive field strength, hardness, and fracture toughness are provided in Table 1.

TABLE-US-00001 TABLE 1 Density 9.71 g/cm.sup.3 Porosity according to ISO xx A00B00C00 Magnetic saturation 20.8 μTm.sup.3kg.sup.−1 Coercive field strength 14.3 kA/m Hardness 1620 HV10 Fracture toughness (Shetty) 8.5 MPa*m.sup.1/2

[0103] After the sintering, the structure was made up of the HEC hard-phase phase, an additional WC hard-phase phase with <5 mass %, and the cobalt binder.

[0104] The amounts of the hardmetal containing HEH determined by means of quantitative X-ray analysis (Rietveld analysis) and the lattice parameter determined for the HEH are thereby provided in Tab. 2.

TABLE-US-00002 TABLE 2 HEH lattice parameter a = 0.43639 +− 0.00003 nm Cobalt content 6.4 +− 2.0 mass % HEH content (cubic) 91.1 +− 1.5 mass %  WC content 2.4 +− 1.0 mass %

EXAMPLE 2

[0105] The milled powder mixture described in Example 1 of the HEH hard phase having the composition (Ta.sub.0.2Nb.sub.0.2Ti.sub.0.2V.sub.0.2W.sub.0.2)C was pressed and sintered with 16 vol % cobalt directly by means of a pressure-assisted sintering aggregate (SPS/FAST from the company FCT Systeme) at a temperature of 1200° C. and a dwell time of 3 min to form disks with a diameter of 20 mm and a height of 6 mm.

[0106] The sample bodies proved to be completely densified under a light microscope. The porosity according to ISO 4505 corresponded to >A02, B00, C00. The Vickers hardness was determined to be 1540 HV10, and the fracture toughness (K.sub.1C) was calculated to be 10.1 MPa*m.sup.1/2 by means of the measurement of the crack lengths and using the formula from Shetty (Shetty 1985—Indentation fracture of WC-Co cermets, see above reference).

[0107] Results of these studies for the density, porosity, magnetic saturation, coercive field strength, hardness, and fracture toughness are provided in Table 3.

TABLE-US-00003 TABLE 3 Density 9.68 g/cm.sup.3 Porosity according to ISO xx A00B00C00 Magnetic saturation 25.2 μTm.sup.3kg.sup.−1 Coercive field strength 11.1 kA/m Hardness 1540 HV10 Fracture toughness (Shetty) 10.1 MPa*m.sup.1/2

[0108] After the sintering, the structure was made up of the HEC hard-phase phase, an additional WC hard-phase phase with <5 mass %, and the cobalt binder enriched with W.

[0109] The amounts of the hardmetal containing HEH determined by means of X-ray analysis and the lattice parameter determined for the HEH are thereby provided in Tab. 4.

TABLE-US-00004 TABLE 4 HEH lattice parameter a = 0.43637 +− 0.00003 nm Cobalt content 11.5 +− 2.0 mass % HEH content (cubic) 85.5 +− 1.5 mass % WC content  3.1 +− 1.0 mass %

EXAMPLE 3

[0110] A single-phase high-entropy hard phase having the composition (Hf.sub.0.2Ta.sub.0.2Zr.sub.0.2Nb.sub.0.2V.sub.0.2)C produced from 20 at. % each of HfC, TaC, ZrC, NbC, and VC by means of a sintering at 1980° C. under vacuum and a subsequent comminution in a ball mill was milled with 16 vol % cobalt (HalfMicron, from UmiCore) in a ball mill in heptane and at a powder/grinding ball ratio of 1:20 for 48 h. Following the drying, the powder was pressed into bending fracture rods having the geometry 45×5×6 mm.sup.3 samples by means of uniaxial pressing at 200 MPa.

[0111] The samples were sintered at 1280° C. for 45 min in a SinterHIP furnace with an HIP pressure of 10 MPa.

[0112] The sample bodies proved to be completely densified under a light microscope. The porosity according to ISO 4505 corresponded to >A02, B00, C00. The Vickers hardness was determined to be 1520 HV10, and the fracture toughness (K.sub.1C) was calculated to be 8.9 MPa*m.sup.1/2 by means of the measurement of the crack lengths and using the formula from Shetty (Shetty 1985—Indentation fracture of WC—Co cermets, see above reference).

[0113] Results of these studies for the density, porosity, magnetic saturation, coercive field strength, hardness, and fracture toughness are provided in Table 5.

TABLE-US-00005 TABLE 5 Density 9.21 g/cm.sup.3 Porosity according to ISO xx A00B00C00 Magnetic saturation 21.9 μTm.sup.3kg.sup.−1 Coercive field strength 13.3 kA/m Hardness 1520 HV10 Fracture toughness (Shetty) 8.9 MPa*m.sup.1/2

[0114] After the sintering, the structure was made up of the HEC hard-phase phase, an additional (Hf,Ta)C hard-phase phase with <2 mass %, and the cobalt binder.

EXAMPLE 4

[0115] A single-phase high-entropy hard phase having the composition (Hf.sub.0.2Ta.sub.0.2Zr.sub.0.2Nb.sub.0.2Ti.sub.0.2)C.sub.0.84N.sub.0.14 produced from 20 at. % each of HfC, TaC, ZrC, NbC, and TiC.sub.0.3N.sub.0.7 by means of a sintering at 2000° C. under nitrogen and a subsequent comminution in a ball mill was milled with 8 vol % cobalt (HalfMicron, from UmiCore) and 8 vol % nickel (2800, from EuroTungsten) in a ball mill in heptane and at a powder/grinding ball ratio of 1:20 for 48 h. Following the drying, bending fracture rods having the geometry 45×5×6 mm.sup.3 samples were pressed from the powder by means of uniaxial pressing at 200 MPa.

[0116] The sample bodies proved to be completely densified under a light microscope. The porosity according to ISO 4505 corresponded to >A04, B00, C00. The Vickers hardness was determined to be 1720 HV10, and the fracture toughness (K.sub.1C) was calculated to be 7.7 MPa*m.sup.1/2 by means of the measurement of the crack lengths and using the formula from Shetty (Shetty 1985—Indentation fracture of WC—Co cermets, see above reference).

[0117] Results of these studies for the density, porosity, magnetic saturation, coercive field strength, hardness, and fracture toughness are provided in Table 6.

TABLE-US-00006 TABLE 6 Density 9.24 g/cm.sup.3 Porosity according to ISO xx A02B00C00 Magnetic saturation 19.1 μTm.sup.3kg.sup.−1 Coercive field strength 9.3 kA/m Hardness 1720 HV10 Fracture toughness (Shetty) 7.7 MPa*m.sup.1/2

EXAMPLE 5

[0118] A single-phase high-entropy hard phase HEH having the composition (Hf.sub.0.25Ta.sub.0.25Zr.sub.0.25Nb.sub.0.25)C.sub.0.975O.sub.0.025 produced from 25 at. % each of HfC.sub.0.9O.sub.0.1, TaC, ZrC, and NbC by means of a sintering at 2000° C. under vacuum and a subsequent comminution in a ball mill was milled with 16 vol % cobalt (HalfMicron, from UmiCore) in a ball mill in a solvent (heptane) and at a powder/grinding ball ratio of 1:20 for 48 h. Following the drying, bending fracture rods having the geometry 45×5×6 mm.sup.3 were pressed from the powder by means of uniaxial pressing at 200 MPa.

[0119] The samples were sintered at 1280° C. for 60 in min a SinterHIP furnace with an HIP pressure of 10 MPa.

[0120] The sample bodies proved to be completely sealed under a light microscope. The porosity according to ISO 4505 corresponded to >A02, B00, C00. The Vickers hardness was determined to be 1420 HV10, and the fracture toughness (K.sub.1C) was calculated to be 8.0 MPa*m.sup.1/2 by means of the measurement of the crack lengths and using the formula from Shetty (Shetty 1985—Indentation fracture of WC—Co cermets).

[0121] Results of these studies for the density, porosity, magnetic saturation, coercive field strength, hardness, and fracture toughness are provided in Table 7.

TABLE-US-00007 TABLE 7 Density 10.40 g/cm.sup.3 Porosity according to ISO xx A00B00C00 Magnetic saturation 21.1 μTm.sup.3kg.sup.−1 Coercive field strength 14.8 kA/m Hardness 1420 HV10 Fracture toughness (Shetty) 8.0 MPa*m.sup.1/2

[0122] After the sintering, the structure was made up of the HEC hard-phase phase, additional hard-phase phases containing Hf-Ta (in the form of an oxycarbide) with <5 mass %, and the cobalt binder.