EP2010687B1 - Hard metal body and method for producing the same - Google Patents

Description

The invention relates to the method defined in the claims for producing a cemented carbide body with a uniform structure, with a single- or multi-phase hard material phase

The invention further relates to the carbide body defined in the claims.

It is known that the grain size of hard metal bodies and their distribution in the hard metal are determined by many factors, including the starting materials, the composition and the production conditions, in particular the grinding and the sintering temperature. In the production of hard metal bodies by powder metallurgy, for example, the carbon balance of the hard metal approach plays a significant role. For carburized carbide alloys, for example, a lower growth tendency is generally observed than for carbides with stoichiometric or superstoichiometric carbon content. Additions of tantalum, vanadium, chromium or even titanium carbide can serve as Kom growth inhibitors for WC. However, the grain size and in particular the grain size distribution of a hard metal has a great influence on the mechanical properties. For example, coarse-grained WC-Co hard metals are generally tougher than fine-grained ones Wear resistance and hardness for it is higher. Mixed crystal phases in multi-carbide alloys can be used to improve toughness.

It is known in the prior art that reduces by additional carbides such as VC, Cr ₃ C ₂ , TaC, NbC, (Ta, Nb) C, or TiC, the grain growth of WC crystallites during sintering and an at least substantially uniform structure can be ensured can. The additional carbides are added either in the form of a WC pre-doped with additional carbides or during the production of the hard metal batch, ie during mixing and grinding. The aim is a uniform distribution of additional carbides as possible. The mixture produced represents a mixture of WC and the additional carbides, which, however, is still inhomogeneous. In particular, the additional carbides can not be incorporated into the crystal lattice of the WC on this production route. Furthermore, WC agglomerates pose a particular problem, since these agglomerates are difficult to break up by grinding and thus the additional carbides are distributed irregularly on the WC crystallites and do not reach all crystallite surfaces. This leads to an undesirable inhomogeneous grain growth of the cemented carbide.

The US-A 4,649,084 describes a method for improving the adhesion of an oxide coating to a WC-based substrate having a composition of WC, Co and at least one carbide, nitride or carbonitride of titanium and at least one carbide, nitride or carbonitride of tantalum, niobium or mixtures thereof. The substrate body is to be sintered in gaseous nitrogen at a temperature at or above the melting point of the cobalt phase for a sufficiently long period of time to cause the formation of a B1-phase enriched layer on the surface of the sintered substrate. Subsequently, the surface of the substrate is oxidized before the oxide wear layer is applied.

The US-A 3,971,656 describes a sintered metal alloy of a metal carbonitride and a binder in which the carbonitride has the form (Ti _x M _y ) (C _u N _v ) _z , where M is a metal of group VI of the periodic table and x + y = 1 and u + v = ₁ and 0.8 ≤ z ≤ 1.07.

In the publication " New Kappa Phases "by E. Reiffenstein et al., Institute of Physical Chemistry, University of Vienna, and Metallwerk Plansee AG Reutte, Tyrol, published 1966 in Mh. Chem., Vol. 97, H. 2/1966 it is stated that in combination there are M- (Mn, Fe, Co, Mi, Cu) -Al-C and W- (Mn, Fe) -Al-C complex carbides which join the kappa phases. The host lattice is related to the Mn ₃ Al ₁₀ type. In turn, a partial lattice occurs in the K carbides, which results from a concatenation of (T ₆ X) octahedra over corners. Aluminum proves to be as favorable for the formation of K phases as it is for η-carbides.

It is an object of the present invention to provide a method for producing a hard metal body and a hard metal body whose grain distribution is substantially homogeneous.

This object is achieved by the measures according to claims 1 and 12 and the dependent claims dependent thereon.

The present invention is based on the idea that the hard metal is produced by reactive sintering a powder mixture containing a W-Co-C phase in the form that the additional carbides incorporated in the crystal lattice of the W-Co-C phase, that is dissolved are or is homogeneously alloyed with these metals. The location of the W-Co-C phases in the ternary system is known in principle. These include, for example, the "M ₆ C" phase, which comprises the concentration range from W ₃ CO ₃ C to W ₄ CPO ₂ C (where M = W, Co), the phase M ₁₂ C (W ₆ Co ₆ C) and a phase close to the composition W ₉ CO ₃ C ₄ . It has been found that solubility of the ternary subcarbide for doping carbides is given to a suitable Total doping level to achieve in the finished sintered carbide. In the unit cell of the crystal lattice of the W-Co-C phases, additional carbides can be incorporated in a uniform distribution. The hard metal is formed by reactive sintering of a batch of a corresponding powder, for example W ₉ CO ₃ C ₄ together with carbon, which after the phase reaction

W ₉ CO ₃ C ₄ + 5C → 9 WC + 3 Co

responding. This cemented carbide has about 9 mass% Co when no additional phases are incorporated. The additional carbides are not included in the above reaction equation; The metals of the additional carbides are in W ₉ Co ₃ C ₄ as well as in all other W-Co-C phases either at the position of the W atoms and / or Co atoms in which these metals are substituted, or they are installed at other point locations in the crystal lattice. In the finished sintered cemented carbide, these metals can be deposited as free carbides in the cemented carbide, optionally on WC crystallites and / or they are dissolved in the binder phase.

Due to the fact that the metals of the additional carbides are incorporated into the unit cell of the ternary phases, they are already present at the points where WC forms in the ternary W-Co-C phase by reactions with carbon, in accordance with the above reaction equation The metals are separated by a distance of less lattice planes so that they occur in the best possible distribution. Hereby, an optimum effect of the doping carbides is achieved not only with respect to the inhomogeneous grain growth to be suppressed, but also ensures economical use since the doping carbides are added only to the extent necessary. In particular, an overdoping of such additional carbides in the hard metal and thus embrittlement of the hard metal can thus be prevented.

Unlike the prior art, a starting powder is used which not only has pure W-Co-C phases to which a growth inhibitor such as Cr ₃ C _{2 is} added, but from the outset an alloyed W-Co-C Phase used in which individual tungsten or cobalt atoms by Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, Ni, Fe, Sc, Y, La, Ce, Re, Ru, Rh, Pt such that these metals are contained in a ternary W-Co-C phase in dissolved form. As a result, inhomogeneous distributions of additional carbides are avoided from the outset. The growth inhibitors are located in the same lattice as the tungsten, which reacts with WC in the presence of carbon.

At least one of the metals Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, of which in particular V, Cr or Ta, and at least one of the metals Sc, Y, La, Ce, Re, Ru, Rh, Pt are preferred contained in dissolved form.

Preferably, the starting mixture contains an amount of said ternary W-Co-C phase which corresponds to at least 10% by volume of the WC-sintered cemented carbide body.

The carbon necessary for the reaction sintering can be added to the batch in solid form as graphite, carbon black or another carbon modification (carbon nanotubes, Buckminster fullerenes) or in the form of another organic or inorganic carbon donor. In the context of the present invention, it is also possible that a part of the carbon required for reactive sintering is added by gas phase treatment with a carbon-containing gas in the pre-sintering or sintering process.

For the preparation of the ternary in principle ternary W-Co-C phase in the starting mixture is a further development of the invention, a selection of W, WC, W ₂ C, tungsten oxides, Co, WCo and C, the desired total composition, in particular the 10 vol % of alloyed ternary phase corresponds, with at least two of the metals Ti, Zr, Hf, V, Nb, Ta, Cr, Mo or at least two oxides, carbides, oxicarbides, carbonitrides or oxicarbonitrides of these metals or an organic compound of these metals such Acetate, oxalate or citrate or another inorganic compound such as a fluoride or chloride and mixed by subsequent annealing in bulk or compressed form at temperatures up to a maximum of 1900 ° C for up to 168 hours under vacuum, inert gas, C-containing Treated gases or hydrogen. According to the invention, the starting mixture can be processed by reaction with carbon either by C-containing gases and / or by addition of carbon in solid form to a powder of the composition WC + Co + doping carbides by a controlled temperature control, preferably in a corresponding total composition necessary for the carbide to be produced ,

During sintering, known sintering cycles, which are tuned to a controlled uniform nucleation of the WC during heating, can be used, wherein the temperature is kept constant in the heating phase, the cooling phase and / or after reaching the maximum sintering temperature in hold times over periods ≥ 5 min or the temperature change is reduced. The starting mixture may additionally contain Al. The same applies to the powders according to claims 9 to 11 as explained for the above method.

End product is a hard metal body with a hard material phase of 60 to 100% by mass of WC (proportion of the hard material phase), up to 40% by mass (proportion of the hard material phase ) of a carbide, nitride, carbonitride or oxycarbonitride of at least one of the metals Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, wherein at least 10% by volume of the WC have been formed by reaction of a ternary W-Co-C phase with carbon and this ternary phase before sintering at least two of the metals Ti, Zr, Hf , V, Nb, Ta, Cr, Mo, Fe, Ni, Sc, Y, La, Ce, Re, Ru, Rh, Pt in dissolved form and a binder phase of 4-20 mass% (hard metal content) of Co or Co with up to 50 mass% (proportion of the binder phase) Fe, Ni and / or Cr.

Nitrogen may also be present in bound form in the powdery starting mixture, in particular as nitride or carbonitride. This nitrogen has a further refining effect in the further production of the cemented carbide body in the finished product.

• Zunächst wurden die Löslichkeiten von V, Ta und Cr, sowohl an heißgepressten Proben als auch an unterkohlten Co-reichen Legierungen des Systems W-Co-C-V-Cr-Ta mittels Hochleistungs-Mikrosondenanalyse unter Verwendung chemisch analysierter, externer Standards ermittelt. Die heißgepressten Proben hatten einen Subcarbidphasenanteil von >95% und wiesen Spuren von freiem VC, Cr₃C₂ und TaC auf, um das Erreichen der Löslichkeitsgrenze für die entsprechenden Metalle in der Subcarbidphase sicherzustellen.

In a first exemplary embodiment, the following procedure was used to produce an alloyed subcarbide powder:

• First, the solubilities of V, Ta and Cr on both hot-pressed samples and carburized Co-rich alloys of the W-Co-CV-Cr-Ta system were determined by high performance microprobe analysis using chemically analyzed external standards. The hot pressed samples had a sub-carbide phase content of> 95% and had traces of free VC, Cr ₃ C ₂ and TaC to ensure reaching the solubility limit for the corresponding metals in the subcarbide phase.

For the subsequent production of the alloyed powder just below (about 10rel%) the solubility limit for V, Ta and Cr, in addition to tungsten carbide, tungsten and cobalt powder, tantalum, vanadium and chromium carbide powder, 0.9 mass% Ta, 0, 4% by mass of VC and 0.4% by mass of Cr ₃ C _{2 are} weighed into a mixture of the formula (W, Ta, V, Cr) _2.51 Co _0.82 C, homogenized in the planetary _{ball mill} in cyclohexane for 20 minutes by means of carbide grinding bodies and ground. After drying, cylindrical molds were pressed at a pressure of 150 MPa and placed in a graphite crucible. It was then heated to 950 ° C under vacuum at a rate of 10 ° C / min, then to 1300 ° C at a rate of 5 ° C / min where the temperature was held for 30 min. At the end of this holding plateau was the addition of 2 x 10 ³ Pa Ar as inert gas. The mixture was then heated to 1350 ° C at a rate of 5 ° C / min and cooled to a holding plateau of 45 min at a rate of first 5 ° C / min, from 950 ° C of 10 ° C / min. The sintered compacts were crushed and the powder pieces ground. This powder was mixed with carbon black and processed in a sintering process to carbide.

In a second embodiment for producing alloyed subcarbide powder, for the production of an alloyed phase (W, Ta, V, Cr) _2.51 Co _0.82 C tungsten carbide, tungsten, cobalt, tantalum carbide, vanadium carbide and chromium carbide powder were weighed in Ta content based on the total Weighing 0.9% by mass and the V and Cr content in each case 0.4% by mass. The powders were homogenized in the planetary ball mill in cyclohexane for 20 minutes using carbide grinding media and ground. The dried and sieved powder mixture was placed in a molybdenum boat under a hydrogen atmosphere at a rate of 5 ° C / min heated to 1350 ° C and held the temperature there for 100 min. The cooling rate was initially 12 ° C / min, from 800 ° C 3 ° C / min. The result was a X-ray single-phase powder of (W, Ta, V, Cr) _2.51 Co _0.82 C.

In a third embodiment for producing rare earth-alloyed subcarbide powder, the following proportions were weighed into a mixture of tungsten carbide, tungsten and cobalt powders, tantalum, vanadium and chromium carbide powders and yttrium nitride: 0.6 mass% TaC, 0.3 Mass% VC, 0.3 mass% Cr ₃ C ₂ and 0.1 mass% YN, again using the general formula (W, Ta, V, Cr, Y) _2.51 Co _0.82 C. YN donates Y by elimination of nitrogen, which dissolves as well as V, Ta, and Cr in the alloyed subcarbide phase. This mixture was homogenized in the planetary ball mill in cyclohexane for 20 minutes using Harlmetallmahlkörpern and ground. The dried and sieved powder mixture was heated in a molybdenum boat under hydrogen atmosphere at 5 ° C / min to 1350 ° C and held the temperature there for 100 min. The cooling curve was initially 12 ° C / min, from 800 ° C 3 ° C / min.

Exemplary embodiments for hard metal production Sintering hard metals with carbon black addition, Example 1

To the above-described powders (W, Ta, V, Cr, Y) _2.51 Co _0.82 C or QN, Ta, V, Cr) _2.51 Co _0.82 C, soot was weighed out so that after sintering a molar [W + V + Ta + Cr] / [C] ratio of 1 was achieved. By means of test sintering and measurement of the specific saturation magnetization, the carbon doping was set exactly. The mixture was homogenized in the Tromrnelmühle under cyclohexane with hard metal Mahlkörpem 20 h and ground. After drying the powder, cylindrical molds were pressed at a pressure of 150 MPa, placed in a graphite crucible, and heated to 1280 ° C under vacuum at a rate of 5 ° C / min. The temperature was held there for 30 min and added 20 mbar Ar as protective gas at the end of this holding plateau. It was then heated at a rate of 5 ° C / min to 1400 ° C and cooled at a holding plateau of 30 min at a rate of 5 ° C / min.

Sintering hard metals with carbon black addition, Example 2

To the powder (W, V, Cr) _2.51 Co _0.82 C was soot weighed, TiC and (Ta, Nb) C, so that after sintering a molar [W + Ti + Nb + Ta] / [C] ratio of about 1 and a proportion of 5 mass% TiC and 10 mass% (Ta, Nb) C, calculated on the total carbide batch, was to be expected. The mixture, which was aimed at the production of P-hard metals, was homogenized, deagglomerated and ground in the drum mill under cyclohexane with hard metal grinding bodies for 20 hours. After drying the powder, cylindrical molds were pressed at a pressure of 150 MPa, placed in a graphite crucible and heated under vacuum at 1290 ° C at a rate of 5 ° C per minute. The temperature was held there for 30 min and at the end of this holding plateau 20 mbar Ar was added as a protective gas. It was then heated at a rate of 5 ° C / min to 1450 ° C and cooled to a holding plateau of 45 min at a rate of 5 ° C per minute. In the microstructure, in addition to WC and Co, a homogeneous cubic phase (Ti, Ta, Nb, Cr, W, V) C appeared.

Sintering hard metals with carbon black addition, Example 3

To the above-described powders (W.Ta, V, Cr) _2.51 Co _0.82 C so much carbon black was weighed in that after sintering, including test sintering, a molar [W + V + Cr] / [C] ratio of about 1 and a spec. Saturation magnetization of 88% of that of pure Co was achieved. The mixture was homogenized in the drum mill under cyclohexane using hard metal grinding bodies for 20 hours and ground. After drying the powder, cylindrical molds were pressed at a pressure of 150 MPa, placed in a graphite crucible and heated to 930 ° C under vacuum at a rate of 5 ° C / min. There, a holding plateau of 45 minutes was inserted and then also heated at a rate of 5 ° C / min to 1280 ° C on. The temperature was held there for 30 min and added at the end of this holding plateau 20mbar Ar as a protective gas. It was then heated at 5 ° C / min to 1400 ° C and cooled to a holding plateau of 30 min at a rate of 5 ° C / min.

Sintering hard metals with carbon black addition, Example 4

To the above-described powders (W, Ta, V, Cr) _2.51 Co _0.82 C, soot was weighed out to set a molar [W + V + Cr] / [C] ratio of 0.95. The mixture was homogenized in the drum mill under cyclohexane using hard metal grinding bodies for 20 hours and ground. After drying the powder, cylindrical molds were pressed at a pressure of 150 MPa, placed in a graphite crucible and heated to 600 ° C under vacuum at a rate of 5 ° C / min. From 600 ° C 700mbar nitrogen were introduced into the sintering furnace and further heated at the same heating rate to 1280 ° C. The temperature was held there for 30 minutes. At the end of this holding plateau, the atmosphere was pumped to a rotary pump vacuum (about 0.01 mbar) and then filled to 100 mbar Ar. It was then heated at a rate of 5 ° C / min to 1400 ° C and cooled at a holding plateau of 30 min at a rate of 5 ° C / min.

Sintering of hard metals with gaseous carbon addition, Example 5

From the ground powder (W, Ta, V, Cr) _2.51 Co _0.82 C described above, green compacts having a quantity of soot significantly below the [W + V + Cr] / [C] ratio of 1 were compacted by means of pressing aids, pressed and placed in a graphite crucible. With addition of a methane / Ar mixture was heated at a rate of 5 ° C / min to 1280 ° C, wherein the Ar / methane ratio was successively increased. The temperature was maintained at 1280 ° for 30 minutes. At the end of this holding plateau pure Ar atmosphere was present. At a rate of 5 ° C / min was further heated to 1400 ° C and cooled after a holding plateau of 30 min at 5 ° C / min.

Properties of the hard metals according to the invention

The hard metals produced all had a reduced grain size and an increased crack toughness according to Palmqvist-Shetty or increased hardness compared to hard metals, which were manufactured from conventional powder formulations. Comparing the hard metals with the conventional ones with identical hardness, this cracking strength K _{1c was} increased by at least 20%; If one compares with the same fracture toughness, the Vickers hardness HV30 was increased by 300-350 HV units (ISO 3878).

The substances and processes described are equally suitable for improving the properties of ultrafine to coarse carbide carbides as well as for improving hard metals with a high proportion of cubic phases (P and M hard metals).

The improved characteristics are due to a more uniform hard metal structure resulting from a uniform distribution of the grain growth inhibiting metals V, Ta and / or Cr. In addition, the significantly improved properties are due to the uniform distribution of Co, which originates entirely from the subcarbide in the cited embodiments. Only by using alloyed subcarbide phases in the approach, this distribution is ideal, since W, Co and the grain growth inhibitors are dissolved in the same crystal lattice of the precursor. The addition of rare earth elements such as Y additionally increases the connection of the interfaces of the WC to Co. The use of nitrogen already in the heating phase and even in the presence of the open-pore structure of the green compacts additionally refines the hard metal structure. This indicates a solution of nitrogen in the alloyed subcarbide phases, which can already be achieved in powder production.

Hard metal of Cr + V + Ta-doped subcarbide phase (Example 6)

Tungsten carbide, tungsten, cobalt, tantalum carbide, vanadium carbide and chromium carbide powders having average grain sizes in the range of 0.6-1.7 microns were weighed into a powder of total composition Co _0.82 (W _2.4 Ta _0.02 V _0.04 Cr _0.04 ) _2.51 C. The starting mixture was homogenized in the planetary ball mill in cyclohexane for 20 min and ground. The dried and sieved powder mixture was heated in a molybdenum boat under hydrogen atmosphere at 5 ° C / min to 1350 ° C and held the temperature there for 100 min. Up to 800 ° C was cooled at 11 ° C / min, then at 3 ° C / min.

To the powder, soot was weighed to obtain a stoichiometric amount of carbon, this mixture was homogenized and ground in the planetary ball mill in hard metal grinding bowls using tungsten carbide balls in cyclohexane for 20 minutes. After drying and granulation were washed with a Pressure of 150 MPa cylindrical molds pressed in a carbide die placed in a graphite crucible.

These green compacts were heated under vacuum at 10 ° C / min to 1280 ° C, the temperature was held there for 30 min and at the end of this holding plateau 20mbar argon was added. The mixture was then further heated at 5 ° C./min to 1400 ° C. and cooled to a holding plateau of 30 min at 5 ° C./min. Metallographically, a typical hard metal microstructure WC + Co resulted, in which additionally a small amount of fine TaC particles could be recognized. Additional Ta as well as all added V and Cr are in dissolved form in the binder.

The hardness HV30 of this cemented carbide was 1690 and the fracture toughness according to Palmqvist / Shetty was 10.6 MPa.m ^-1/2 .

Carbide of Cr + V-doped Subcarbidphase (Example 7)

Tungsten carbide, tungsten, cobalt, tantalum carbide, vanadium carbide and chromium carbide powders of average grain sizes in the range 0.6-1.7 microns were weighed into a powder of total composition Co _0.82 (W _2.42 V _0.04 Cr _0.04 ) _2.51 C. The mixture of the starting powders was homogenized in the planetary ball mill in cyclohexane for 20 min and ground. The dried and sieved powder mixture was heated in a molybdenum boat under hydrogen atmosphere at 5 ° C / min to 1350 ° C and held the temperature there for 100 min. Up to 800 ° C was cooled at 11 ° C / min, then at 3 ° C / min.

To the thus-obtained powder, carbon black was weighed to a theoretical (W, Cr, V) / C ratio of 0.94, homogenized and ground in the planetary ball mill in hard metal grinding jars using hard metal balls in cyclohexane for 20 minutes. After drying, cylindrical molds were pressed in a carbide die at a pressure of 150 MPa and placed in a graphite crucible. The green compacts were heated at 5 ° C / min to 930 ° C. There, a holding plateau of 45 min was inserted and then also heated at 5 ° C / min to 1280 ° C on. Here, the temperature was maintained for 30 min and then 20mbar argon added as a protective gas. At 5 ° C / min was further heated to 1400 ° C and cooled to a holding plateau of 30min at 5 ° C / min. The metallographic preparation gave a typical biphasic Hard metal structure WC + Co, the alloying elements V and Cr are in dissolved form in the co-binder.

The hardness HV30 of this cemented carbide was 1430 and the fracture toughness according to Palmqvist / Shetty 15.5 MPa.m ^-1/2 .

Claims (12)

1. Method for producing a hard metal body having a microstructure of which the anisotropic WC crystallites make up less than 20% of the total number of WC crystallites,

   - having a hard material phase which contains 60% by mass to 100% by mass WC, up to 40% by mass of a free carbide, nitride, carbonitride or oxycarbonitride of one of the elements Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and

   - having a binder phase of Co or of Co and up to 50% by mass Ni, Fe or Cr which has a proportion of 4-20% by mass of the overall hard metal,
   in which method a powdery starting mixture corresponding to the desired composition is made up and subjected to reactive sintering in the presence of carbon,
   characterized
   in that the powdery starting mixture has at least one in principle ternary W-Co-C phase, in which at least two of the metals Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, Ni, Fe, Sc, Y, La, Ce, Re, Ru, Rh, Pt are present in dissolved form.
2. Method according to Claim 1, characterized in that one of the metals Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, preferably V, Cr or Ta, and at least one of the metals Sc, Y, La, Ce, Re, Ru, Rh, Pt are present in dissolved form and/or in that a quantity of said in principle ternary W-Co-C phase which corresponds to at least 10% by volume of the WC in the sintered hard metal body is present in the starting mixture.
3. Method according to Claim 1 or 2, characterized in that the carbon required for reactive sintering is admixed to the batch in solid form of graphite, carbon black or some other carbon modification or some other organic or inorganic carbon donor or mixtures of said substances and/or in that some of the carbon required for reactive sintering is added by gas-phase treatment with a carbon-containing gas during the presintering or sintering process.
4. Method according to one of Claims 1 to 3, characterized in that, to produce the in principle ternary W-Co-C phase in the starting mixture, a selection of W, WC, W₂C, tungsten oxides, Co, W_xCo_y and C which corresponds to the desired overall composition, in particular to the 10% by volume proportion of alloyed, ternary W-Co-C phase, is mixed with at least two of the metals Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, Fe, Ni, Sc, Y, La, Ce, Re, Ru, Rh, Pt or at least two oxides, carbides, oxycarbides, carbonitrides or oxycarbonitrides of said metals or two organic compounds of said metals such as acetate, oxalate or citrate or a further inorganic compound such as a fluoride or chloride, or contains at least two of the aforementioned metals in dissolved form, and is treated by subsequent annealing in a loose bulk bed or compacted form at temperatures of up to at most 1900°C for up to 168 hours under a vacuum, protective gas, C-containing gases or hydrogen, preferably in such a manner that the starting mixture is processed by reactions with carbon either by C-containing gases and/or by the addition of carbon in solid form to form a powder of the composition WC + Co + doping carbide or to form a powder WC + Co(Me), where Co(Me) indicates a Co alloy of at least two of the elements Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, Fe, Ni, Sc, Y, La, Ce, Re, Ru, Rh, Pt, by a controlled temperature management, preferably in a required overall composition corresponding to the hard metal to be produced.
5. Method according to one of Claims 1 to 4, characterized in that nitrogen is present in the powdery starting mixture in bonded form, in particular as a nitride or carbonitride.
6. Method according to one of Claims 1 to 5, characterized in that the temperature is kept constant in holding times over periods of time ≥ 5 min or the change in temperature is reduced during the sintering in the heating phase, the cooling phase and/or after the maximum sintering temperature has been reached.
7. Method according to one of Claims 1 to 6, characterized in that Al is additionally present in the starting mixture.
8. Method according to one of Claims 1 to 7, characterized in that the sintering is carried out using conventional vacuum sintering cycles, sintering cycles with a reducing atmosphere or protective gas atmosphere or conventional sintering HIP cycles up to temperatures of 1500°C, wherein heating and cooling rates of 2-15°C/min are observed and at least one isothermal temperature section may be present in the temperature range of 1100 to 1350°C with a duration of 10 to 100 min during the heating.
9. Method according to one of Claims 1 to 8, characterized by the use of sintering cycles up to temperatures of 1500°C, which is adapted for the reaction sintering in such a manner as to take into account a controlled, uniform nucleation of WC or a controlled disintegration of the W-Co-C phase during heating in such a manner that the section of the sintering cycle in which the subcarbide phase disintegrates, preferably in the range of 750 to 1100°C, is undertaken with a heating rate lower than 2°C/min, preferably at 0.1 to 2°C/min, or one or more additional holding times, preferably with a duration of 10 min to 2 h, are set therein.
10. Method according to one of Claims 1 to 9, characterized in that, in addition to the alloyed ternary powder according to Claims 4 to 6, an additional proportion of at least one of the metals Al, Co, Ni, Fe, Sc, Y, La, Ce, Re, Ru, Rh, Pt or a carbide, oxide, carbonitride or oxycarbonitride of the metals Al, Co, Ni, Fe, Sc, Y, La, Ce, Re, Ru, Rh, Pt is introduced into the batch.
11. Method according to one of Claims 1 to 10, characterized in that the sintering is carried out by using a nitrogen atmosphere or a nitrogen-containing atmosphere preferably at a pressure of 1 to 7 x 10⁴ Pa, preferably in the range of 800 to 1200°C, in which the solid-state reaction of the W-Co-C phase takes place and therefore this reaction and the carbon balance of the hard metal can be influenced.
12. Hard metal body having a 4 to 20% by mass binder phase which preferably contains Co or Co and up to 50% by mass, in particular 0.5 to 50% by mass, Fe, Ni and/or Cr, and also a hard material phase which contains up to 40% by mass, preferably 5% by mass to 25% by mass, of a carbide, nitride, carbonitride or oxycarbonitride of at least one of the metals Ti, Zr, Hf, V, Ta, Cr, Mo, remainder WC, characterized in that at least 10% by volume of the WC has formed by reaction of an in principle ternary W-Co-C phase with carbon, wherein this ternary W-Co-C phase contains at least two of the metals Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, Fe, Ni, Sc, Y, La, Ce, Re, Ru, Rh, Pt in dissolved form before the sintering.