WO1998021147A1

WO1998021147A1 - Method for producing oxygen-containing hard materials and their use

Info

Publication number: WO1998021147A1
Application number: PCT/EP1997/006137
Authority: WO
Inventors: Lutz-Michael Berger; Andreas Krell; Eckart Langholf
Original assignee: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
Priority date: 1996-11-09
Filing date: 1997-11-06
Publication date: 1998-05-22
Also published as: DE19646333A1; DE19646333C2

Abstract

The invention relates to the area of and concerns a method for producing oxygen-containing hard materials, which can be used for instance in bearings. The invention has the task of providing a simple method for producing oxygen-containing hard materials with stoichiometric and substoichiometric compositions. According to the invention, this is done by grinding with carbon and homogenizing an oxide of the metals of the IV and V subgroup of the PTE, or mixtures of oxides of the metals of the IV, V and VI subgroup, or one or more metals of the IV and/or V subgroup or of the IV and V and VI or of the IV and VI or of the V and VI subgroup and one or more oxides of the metals of the IV, V and VI subgroup, the powder mixture being heated continuously or discontinuously at a temperature of up to 2,500 °C.

Description

Process for the production of oxygen-containing hard materials and their use

Technical field

The invention relates to the field of ceramics and hard metals and relates to a method for producing oxygen-containing hard materials which are used in composite materials, e.g. for bearings, for indexable inserts, as an abrasive or as a magnetic head substrate.

State of the art

Numerous, simple and also complicated processes for producing hard materials from carbides, nitrides or carbonitrides are known. There are hard materials with defined compositions or purity (US 5,314,656, DE 42 16 802, DE 41 25 505, EP 391 150, EP 440 157) and / or defined morphology, preferably of a spherical type (US 5,417,952, US 5,380,688, DE 38 48 036 ) and / or with narrow grain size distributions of fine or coarse grains (EP 0 693 456, EP 543 751, EP 447 388, DD 287 959).

For the synthesis of hard materials (carbides, nitrides and carbonitrides) from one or more metals of IV., V. and VI. Subgroup of the Periodic Table of the Elements (PSE), essentially three methods are known.

The first basic process relates to the direct carburization / nitration of metals and their hydrides. This process has the disadvantage that it is very difficult to carry out and this also leads to a strong agglomeration of the reaction products. Long periods of time are needed to destroy the agglomerates

CONFIRMATION COPY Grinding necessary. In addition, the metallic starting materials to be used are relatively expensive.

As a second method, deposition processes, e.g. CVD known, which are mainly used for surface coating. In the coating of hard metals, occasionally oxide-containing titanium layers have become known (EP 537 741, JP 02057616, JP 02015159, JP 01197364, JP 61272343, JP 53-60808). These oxide-containing layers increase the oxidation resistance, hardness and abrasion resistance of cutting tools. Larger amounts of hard materials cannot be produced with this process.

The carbothermal reduction of the oxides of the metals by carbon is known as the third method. This process is known as the simplest and most economically effective process, but it also has disadvantages in terms of purity, grain size and their distributions or grain shape of the hard materials.

EP 693 456 specifies a process for producing spherical nitride and / or carbonitride powder of titanium, in which the oxide of the metal is intimately mixed with carbon and then reacted at temperatures between 1400 ° C. and 2000 ° C. The reaction space is then evacuated and the reaction mixture is then flooded several times with a nitrogen-containing atmosphere at a pressure of 5 to 100 kPa and temperatures between 2000 and 2400 ° C. and evacuated again.

The composition of this powder is at 11, 7% Cg _it; <0.05% Cf _re j; 9.1% N; 0.12% O given. A stoichiometry of x + y + z = 0.986 (with x = 0.589, y = 0.393, z = 0.0045) can be calculated from this.

Due to the very long dwell times of the synthesis (4 - 5 h) and subsequent repeated evacuation and flooding, the generation becomes coarse, spherical Carbonitride powder described The reaction products were ground with carbide balls damp (in gasoline) for 30 min after cooling in an Attntor. It can be assumed that the distribution of the grain sizes, which according to the definition given there, has a narrow grain size range if the values between d | o ^unc '^ 90 smaller than 20 μm, due to the very long meals being reached in the attentor. No information was given on the grain distributions. At the same time, however, it can be assumed that a spherical grain shape is not achieved by the long meals, rather a powder is added split-edged grain shape and possibly produced with a broad grain spectrum The average grain sizes are in a range> 2 μm, preferably> 3 μm

The disadvantage of this method is essentially that a stochiometric composition is to be achieved, the oxygen content in the hard material being assumed to be as low as possible <0.5% by weight. Such an oxygen content leads to a z value when converted into stochiometric information of at most 0.05, the stochiometric composition is essentially achieved by the long synthesis times and the high temperatures that are used in this process

A process is described in US Pat. No. 5,417,952 in which titanium dioxide powder with a very small grain size is coated by means of a carbon-containing atmosphere in the temperature range from 200 ° C. to 1000 ° C. In a second step, the carbon is released at temperatures between 1200 ° C. and 1600 ° C. under a nitrogen-donating atmosphere and nitrogen and a stochiometric carbonite TιC _x Ny with x + y = 1 and x> 0 and y <1 generated The grain sizes generated with this method lie in a range from 0.05 μm to 0.2 μm

A process is described in US Pat. No. 5,380,688 for the production of as fine as possible, oxygen-free hard material powder provides carbothermal reduction, which are between 100 K s and 100 000 000 K / s and can only be achieved in a reactor provided for this purpose. Oxides of the metals and carbon (preferably carbon black) are mixed and then at a heating rate, preferably between 10,000 K / s and 100,000,000 K / s heated to temperatures between 1400 ° C and 2400 ° C. The dwell times in the reaction space required for the carbothermal reductions range from 0.2 s to 0.5 h depending on the reduction carried out. For the carbothermal reduction of Titanium oxide requires average holding times of 2 mm to 2.75 mm and temperatures of 1550 ° C to 1950 ° C and stoichiometric TiC is formed

No. 5,314,656 describes a process for the production of TICQ 5N0 5, which is characterized by two successive steps. In the first step, a substochiometric carbide TiCrj 5 is produced, which in a nitrogen-containing atmosphere is converted into a stochiometric carbonitride (x + y = 1 in a second step ) The transition metal (in the example titanium) is mixed with carbon in a molar ratio 2 1 and implemented in a nitrogenous atmosphere by means of self-propagating high-temperature synthesis (SHS). The detection of the composition of the cubic phase (substochiometric TiCj ^) was determined by the determination of the lattice parameter. The determination of the composition via the lattice parameter of the cubic phase is an inadequate method. Conclusions regarding the composition of the cubic phase can only be derived from chemical analysis

DD 287 959 describes the formation of low-oxygen, coarse substochiometric carbides, which coarsen at temperatures above 2000 ° C. Subsequently, carbonitrides with a composition MeC _x N _v with y> 0, 1 and x + y> 0.7. Overall, the method is aimed at achieving stoichiometric or near-stoichiometric compositions, an intermediate sub-stoichiometry being accepted in the course of the method. This can also be seen from the exemplary embodiments given.

It is known that such materials were produced from the individual components for physicochemical investigations in the pseudoternary system TiC - TiN - TiO. The TiO was produced in an additional synthesis step from TiO 2 and Ti (Mh. Chemie, 103 [4], 1972, 1130-1137; Zh. Prikl. Khim. 44 [7] 1971, 1646-1648). Elsewhere, a slightly oxygen-contaminated titanium carbide, TiO not described synthesis and metallic titanium were used for the synthesis in the Ti-C-O system (Izv. Akad. Nauk. SSSR, Neorg. Mater. 6 [8], 1970, 1405-1408).

It is also known that oxycarbides are formed during the carbothermal reduction of TiÜ2 with carbons (with a mixture in a molar ratio of 1: 3); these are stoichiometric with contents of z <0.4% in the reaction in an inert atmosphere. Stoichiometric oxycarbonitrides are formed in a nitrogenous atmosphere (Int. J. Refractory Metals & Hard Materials 12 [4] 1993-94, 161-172). A disadvantage of the described TiO2: carbon molar ratios of 1: 3 is that the synthesis products typically have a high free carbon content> 2%.

The disadvantage of the known methods is that hard materials with a stoichiometric composition which are as free from oxygen as possible have been produced, which can reduce the higher free carbon contents only by long holding times, high synthesis temperatures or by further reactions. Presentation of the invention

The object of the invention is then to provide a simple process for the production of oxygen-containing hard materials in a stochiometric and substochiometric composition

The object is achieved by the invention specified in the claims

In the process according to the invention for the production of oxygen-containing hard materials in a stochiometric or substochiometric composition, an oxide of the metals of the IV and V subgroup of the PSE, or mixtures of the oxides of the metals of the IV, V and VI subgroup of the PSE, or one or more metals of the IV and / or V subgroup of PSE or IV and V and VI or IV and VI or V and VI subgroup of PSE and one or more oxides of metals from IV, V and VI subgroup of PSE, ground with carbon and homogenized , where a molar ratio corresponding to the stochiometric composition Me (C _x N _v O _z ) with x + y + z «1 and z> 0.1 and Me = metals of the IV and / or V subgroup of the PSE or of the IV and V and VI or the IV and VI or the V and VI subgroup of the PSE, or according to the substochiometric composition Me (C _x N _y O _z ) with x + y + z <0.95 and z> 0.05 and Me = metals of IV and / or V subgroup of the PSE or IV and V and VI or the IV and VI or the V and VI subgroup of the PSE is set, the powder mixture is heated continuously or discontinuously to a temperature of up to 2500 ° C., the holding times for discontinuous heating in the respective stages being between 1 mm and 5 h , and the powder mixture is then cooled to room temperature after one or more holding times or in the case of discontinuous heating In the method according to the invention, an inert and / or nitrogen-containing and / or hydrogen-containing and / or carbon-containing and / or other reducing atmosphere is advantageously set as an atmosphere or a vacuum during heating and / or during the holding time and / or during cooling.

There are particular advantages if, after grinding, the powder mixture is first heated in a reducing atmosphere to a temperature between 1150 ° C. and 1600 ° C., then kept at this temperature for up to 1 h and then cooled to room temperature, and then this powder mixture is in the Vacuum heated to a temperature between 1350 ° C and 1800 ° C, held there for 2 h and then cooled back to room temperature.

It is also expedient if, after grinding, the powder mixture is first heated to a temperature of up to 2000 ° C. in a reducing or inert atmosphere, then kept at this temperature for up to 3 hours and then this powder mixture is vacuumed to a temperature above 1600 ° C. preferably between 2000 ° C and 2500 ° C, heated, held there for 5 h and then cooled again to room temperature.

According to an advantageous embodiment of the method according to the invention, a carbon with a proportion of oxygen in the range from 0.1 to 25% by mass is used as carbon.

There are particular advantages if a carbon with a proportion of oxygen in the range from 5 to 20% by mass is used as carbon.

There are also advantages if a molar ratio R _x : C = 1: 1 to 1: x + p is achieved in order to set a stoichiometric oxygen-containing or a substoichiometric oxygen-containing composition, where R one or more metals of subgroup IV, and / or V of PSE or metals of

IV and V and VI or the IV and VI or the V and VI subgroup of the PSE and one or more oxides of these metals, or mixtures of the oxides of these metals or an oxide of these metals, and x = 2 for oxides of the IV subgroup of the PSE, x = 2.5 for oxides of the V subgroup of the PSE, x = 3 for oxides of the VI subgroup of the PSE or, in the case of oxide mixtures, the sum of all x of all individual oxides, and p is the sum of the oxides and metals contained in the starting mixture

There are also advantages if a molar ratio R _x C = 1 1 to 1 (x + p-0.05) is set in order to set a stoichiometric oxygen-containing or a substoichiometric oxygen-containing composition, where R is one or more metals of IV, and / or V. Subgroup of PSE or metals of IV and V and VI or IV and VI or V and VI subgroup of PSE and one or more oxides of these metals, or mixtures of the oxides of these metals or an oxide of these metals, and x = 2 for oxides the IV subgroup of the PSE, x = 2.5 for oxides of the V subgroup of the PSE, x = 3 for oxides of the VI subgroup of the PSE or, in the case of oxide mixtures, the sum of all x of all individual oxides and p the sum of the oxides and metals contained in the starting mixture is

It is also advantageous if a molar ratio R _x C = 1 1 to 1 (x + p-0.15) is set to adjust a stoichiometric oxygen-containing or a substoichiometric oxygen-containing composition, where R is one or more metals of IV, and / or V subgroup of PSE or metals of IV and

V and VI or the IV and VI or the V and VI subgroup of the PSE and one or more oxides of these metals, or mixtures of the oxides of these metals or an oxide of these metals, and x = 2 for oxides of the IV subgroup of the PSE, x = 2.5 for oxides of the V subgroup of the PSE, x = 3 for oxides of the VI subgroup of the PSE or, in the case of oxide mixtures, the sum of all x of all individual oxides, and p is the sum of the oxides and metals contained in the starting mixture It is furthermore advantageous if a molar ratio R _x : C = 1: 1 to 1: 2.95 is achieved in order to set a stoichiometric oxygen-containing or a sub-stoichiometric oxygen-containing composition, where R is an oxide of a metal of subgroup IV of the PSE and x = 2 is.

There are particular advantages if a molar ratio R _x : C = 1: 1 to 1: 2.85 is achieved to adjust a stoichiometric oxygen-containing or a sub-stoichiometric oxygen-containing composition, where R is an oxide of a metal of subgroup IV of the PSE and x = 2 is.

It is also advantageous if a molar ratio R _x : C = 1: 1 to 1: 3.45 is realized in order to set a stoichiometric oxygen-containing or a sub-stoichiometric oxygen-containing composition, where R is an oxide of a metal from subgroup V of the PSE and x = 2.5 is.

Here, too, there are particular advantages if a molar ratio R _x : C = 1: 1 to 1: 3.35 is achieved in order to set a stoichiometric oxygen-containing or a substoichiometric oxygen-containing composition, where R is an oxide of a metal from subgroup V. of the PSE and x = 2.5.

According to the invention, the hard materials produced according to the invention are used in composite materials for bearings, for indexable inserts, as an abrasive or as a magnetic head substrate.

The oxygen-containing hard materials are advantageously used in composite materials made of oxygen-containing hard materials and oxides, in particular for a black ceramic. It is also advantageous if oxygen-containing hard materials according to claim 12 with an average grain size of> 5 μm are used for coating steels.

The invention is based on the surprising finding that a previously unknown sub-stoichiometry can be set for the oxygen-containing hard materials produced according to the invention and that a stoichiometric composition can also be produced in this way.

Since it has previously been generally assumed that the use of hard materials with higher oxygen contents in composite materials leads to a severe deterioration in the properties, it was surprising that this did not occur when the oxygen-containing hard materials according to the invention were used. On the contrary, it has been shown that not only have the properties not deteriorated, but they have partially improved and other advantages have arisen.

Oxygen-containing hard materials according to the present invention are to be understood as meaning oxicarbides, oxynitrides, oxicarbonitrides, mixed oxyarbides, mixed oxynitrides and mixed oxycarbonitrides.

Another advantage of the oxygen-containing hard materials produced according to the invention is that even coarser-grained starting powders can be used for their production without this having any negative effects on the use of the hard materials.

In addition, sintered ceramics with a relatively dense, fine-grained structure and comparatively high hardness can be produced from coarse-grained, oxygen-containing hard materials. Furthermore, the process according to the invention produces oxygen-containing hard materials which have a relatively low proportion of free carbon, which has a very advantageous effect on the process implementation, since higher temperatures, long synthesis times and / or subsequent additional reactions can be avoided.

With regard to the problem of substoichiometry in the production of hard materials by carbothermal reduction, it can be said that, surprisingly, in our own experiments it was found that the carbon content in the resulting hard material initially settled to a certain level, while the oxycarbide produced lost more and more oxygen. A sub-stoichiometry is formed, the size of which depends on the temperature, time, pressure and atmosphere. During this process period, carbon and oxygen are not exchanged in a 1: 1 ratio in the resulting cubic hard material. This means that the carbothermal reduction can be carried out in such a way that an oxygen-containing hard material with a desired stoichiometry or sub-stoichiometry is produced by stopping the reduction at a certain point in time. At what point in time which sub-stoichiometry is reached, the person skilled in the art can easily deduce from the known reaction equations.

Surprisingly, such oxygen-containing hard materials produced according to the invention not only cause no deterioration in properties when used in sintered ceramics, as would be expected according to the general expert opinion, but sometimes even improvements in properties.

A two-stage process is used to produce fine-grained hard material powder, in particular <2 μm. In the first process step, the starting powder mixture is heated to a temperature between 1150 ° C. and 1600 ° C. in a reducing atmosphere and held there for 1 hour. This powder mixture is then heated in a vacuum to a temperature between 1350 ° C. and 1800 ° C., held for 2 hours and then cooled to room temperature. This has resulted in a very fine-grained hard material powder with a comparatively high oxygen content and a low free carbon content.

By changing the molar ratios of the starting materials with a view to reducing the available carbon in the starting mixture, the free carbon content of the end product is advantageously influenced and reduced overall.

If the aim is to produce a coarser hard material powder with average grain sizes of> 2 μm according to the invention, the starting powder mixture is to be heated to a temperature of up to 2000 ° C. in a first synthesis step under a reducing or inert atmosphere and held there for 3 hours. The powder mixture is then heated under vacuum to temperatures above 1600 ° C., preferably between 2000 ° C. and 2500 ° C., held there for up to 5 hours and then cooled to room temperature. The desired grain growth takes place primarily in the second stage.

Coarser hard material powder, in particular with an average grain size of> 5 μm, is used, for example, in the coating of steels. This coating is carried out by means of laser entry. The use of this coarser hard material powder is advantageous in this method because the hard material grains are not melted during the coating and thus improve the surface strength and wear resistance of the steels. Best way to carry out the invention

The invention is explained in more detail using several exemplary embodiments.

example 1

216 g of TiÜ2 and 84 g of carbon black, which corresponds to a molar ratio of 1: 2.6, are homogenized in a roller mixer. This is followed by a 15-hour dry grinding in a ball mill in stainless steel containers and with hard metal balls (diameter approx. 10 mm) with a mass ratio of 1 5

Temperature treatment is carried out in an oven with graphite heating elements with 30 g portions stuffed in graphite crucibles. The furnace is heated to a temperature of 1500 ° C. at a heating rate of 50 K / min and then to a temperature of 1600 ° C. at 20 K / min. During the heating process, 100 l / h of argon are flowed through the furnace. The pressure at the end of the holding time is 8.5 x 10 ^-2 MPa. The temperature is kept at 1600 ° C. for 15 minutes and the furnace is evacuated during this time. The mixture is then heated to 2000 ° C. under constant evacuation at a heating rate of 20 K / min and held there for 60 min. At the end of the holding time, the pressure is 5.5 x 10 ^{~ 5} MPa. By lowering the graphite crucible into a cooling chamber, the samples are quickly cooled to room temperature. The resulting agglomerated hard material powder is comminuted in a vibrating disc mill at 1400 rpm for 60 s.

This process resulted in an oxygen-containing hard material powder with the composition TiCrjjsOo i, which has 0.12% by mass of free carbon and has a surface area (BET) of 0.97 m 2 / g. The average grain size is 4.1 μm. Example 2

207 g TiO 2 and 93 g activated carbon (14% oxygen), which corresponds to a molar ratio of 1: 3, are homogenized in a roller mixer. This is followed by a 15-hour dry grinding in a ball mill in stainless steel containers and with hard metal balls (diameter approx. 10 mm) with a mass ratio of 1: 5. The temperature treatment is carried out in an oven with graphite heating elements with 20 g portions stuffed in graphite crucibles. The furnace is heated to a temperature of 1600 ° C. at a heating rate of 50 K / min and held there for 30 minutes. Throughout the synthesis, 100 l / h of argon are flowed through the furnace. By lowering the graphite crucible into a cooling chamber, the samples are quickly cooled to room temperature. The resulting agglomerated hard material powder is comminuted in a vibrating disc mill at 1400 rpm for 60 s.

This process results in an oxygen-containing hard material powder of the composition

emerged, which has 0.07 mass% free carbon and has a surface area (BET) of 3.0 m2 / g.

Example 3

207 g TiO 2 and 93 g activated carbon (14% oxygen), which corresponds to a molar ratio of 1: 3, are homogenized in a roller mixer. This is followed by a 15-hour dry grinding in a ball mill in stainless steel containers and with hard metal balls (diameter approx. 10 mm) with a mass ratio of 1: 5. The temperature treatment is carried out in an oven with graphite heating elements with 20 g portions stuffed in graphite crucibles. With a heating rate of 50 K / min the furnace is heated to a temperature of 1500 ° C and then heated at 20 K / min to a temperature of 1600 ° C. During the heating process, 100 l / h of argon are flowed through the furnace. The oven is evacuated for 15 minutes at a temperature of 1600 ° C. The mixture is then heated to 1800 ° C. under constant evacuation at a heating rate of 20 K / min and held there for 30 minutes. By lowering the graphite crucible into a cooling chamber, the samples are quickly cooled to room temperature.

emerged, which has 0.07 mass% free carbon and has a surface area (BET) of 1.5 m ² / g. The mean grain size is 1.75 μm (d _{1 5 | 9} o _{/ o} = 0.24 μm, d ₈₄ o / ₀ = 7.47 μm).

Example 4

77.1 g TiO 2 and 177.1 g tungsten and 45.8 g graphite, which corresponds to a molar ratio of 1: 3.95 (x = 2; p = 2), are homogenized in a roller mixer. This is followed by a 15-hour dry grinding in a ball mill in stainless steel containers and with hard metal balls (diameter approx. 10 mm) with a mass ratio of 1: 5. The temperature treatment is carried out in an oven with graphite heating elements with 20 g portions stuffed in graphite crucibles. The furnace is heated to a temperature of 1800 ° C. at a heating rate of 20 K / min. During the heating process, 100 l / h of helium are flowed through the furnace. The temperature is maintained at this temperature for 120 minutes and then the samples are cooled in the cooling chamber.

This process has resulted in an oxygen-containing hard material powder of the composition (Ti.WJCrj ygOo g, which has 0.1% by mass of free carbon and has a surface area (BET) of 2.0 m ² / g. Example 5

166.1 g ZrÜ2 and 179.2 g Nb2θs and 104.7 g carbon black, which corresponds to a molar ratio of 1: 6.45 (x = 4.5; p = 2), are homogenized in a roller mixer. This is followed by a 15-hour dry grinding in a ball mill in stainless steel containers and with hard metal balls (diameter approx. 10 mm) with a mass ratio of 1: 5. The temperature treatment is carried out in an oven with graphite heating elements with 20 g portions stuffed in graphite crucibles. The furnace is heated to a temperature of 1700 ° C at a heating rate of 50 K / min. During the heating process, 100 l / h of hydrogen are passed through the furnace. The temperature is maintained at this temperature for 120 minutes and then the samples are cooled in the cooling chamber. The samples are then heated under vacuum to a temperature of 1600 ° C. at a heating rate of 50 K / min and held at this temperature for 60 min. The pressure at the end of the holding time is 6 x10 " ⁵ MPa.

This process has resulted in an oxygen-containing hard material powder of the composition (Zr, Nb) Co _ι 83θθ, 15, which has 0.09 mass% of free carbon and a surface area (BET) of 1.0 m ² / g.

Claims

claims

1. Process for the production of oxygen-containing hard materials in a stoichiometric or substoichiometric composition, in which an oxide of the metals of the IV. And V. subgroup of the PSE, or mixtures of the oxides of the metals of the IV., V. and VI. Sub-group of the PSE, or one or more metals of the IV. And / or V. Sub-group of the PSE or the IV. And V. and VI. or the IV. and VI. or the V. and VI. Sub-group of the PSE and one or more oxides of the metals of IV., V. and VI. Subgroup of the PSE, ground with carbon and homogenized, with a molar ratio corresponding to the stoichiometric composition

with x + y + z «1 and z> 0.1 and Me = metals of the IV. and / or V. subgroup of the PSE or of the IV. and V. and VI. or the IV. and VI. or the V. and VI. Subgroup of the PSE, or according to the substoichiometric composition Me (C _x N _v O _z ) with x + y + z <0.95 and z> 0.05 and Me = metals of the IV. And / or V. subgroup of the PSE or the IV. and V. and VI. or the IV. and VI. or the V. and VI. Sub-group of the PSE is set, the powder mixture is heated continuously or discontinuously to a temperature of up to 2500 ° C, the holding times for discontinuous heating in the respective stages being between 1 min and 5 h, and the powder mixture subsequently or with discontinuous heating after one or several holding times is cooled to room temperature.

2. The method according to claim 1, in which an inert and / or nitrogen-containing and / or hydrogen-containing and / or carbon-containing and / or a reducing atmosphere other than atmosphere or a vacuum during heating and / or during the holding time and / or during cooling is set .

3. The method according to claim 1 and 2, wherein the powder mixture after grinding first in a reducing atmosphere to a temperature between 1150 ° C and Heated to 1600 ° C, held there for 1 h and then cooled to room temperature, and then this powder mixture was heated in vacuo to a temperature between 1350 ° C and 1800 ° C, held there for 2 h and then cooled to room temperature.

4. The method according to claim 1 and 2, wherein the powder mixture after grinding is first heated in a reducing or inert atmosphere to a temperature up to 2000 ° C and held there for 3 h, and then this powder mixture in vacuo to a temperature above 1600 ° C, preferably between 2000 ° C and 2500 ° C, heated, held there for 5 h and then cooled to room temperature.

5. The method according to claim 1, in which a carbon with a proportion of oxygen in the range of 0.1 to 25% by mass is used as carbon.

6. The method according to claim 5, in which a carbon with a proportion of oxygen in the range from 5 to 20% by mass is used as carbon.

7. The method according to claim 5 and 6, in which a molar ratio R _x : C = 1: 1 to 1: x + p is set to adjust a stoichiometric oxygen-containing or a sub-stoichiometric oxygen-containing composition, wherein R one or more metals of IV. and / or V. Subgroup of PSE or metals of IV. and V. and VI. or the IV. and VI. or the V. and VI. Sub-group of the PSE and one or more oxides of these metals, or mixtures of the oxides of these metals or an oxide of these metals, and x = 2 for oxides of the IV. Sub-group of the PSE, x = 2.5 for oxides of the V. sub-group of the PSE, x = 3 for oxides of VI. Subgroup of the PSE or, in the case of oxide mixtures, the sum of all x of all individual oxides, and p is the sum of the oxides and metals contained in the starting mixture.

8. The method according to claim 5 and 6, in which a molar ratio R _x : C = 1: 1 to 1: (x + p-0.05) is set to adjust a stoichiometric oxygen-containing or a substoichiometric oxygen-containing composition, wherein R is a or several metals of IV. and / or V. subgroup of PSE or metals of IV. and V. and VI. or the IV. and VI. or the V. and VI. Sub-group of the PSE and one or more oxides of these metals, or mixtures of the oxides of these metals or an oxide of these metals, and x = 2 for oxides of the IV. Sub-group of the PSE, x = 2.5 for oxides of the V. sub-group of the PSE, x = 3 for oxides of VI. Subgroup of the PSE or, in the case of oxide mixtures, the sum of all x of all individual oxides, and p is the sum of the oxides and metals contained in the starting mixture.

9. The method according to claim 5 and 6, in which a molar ratio R _x : C = 1: 1 to 1: (x + p-0.15) is set to adjust a stoichiometric oxygen-containing or a substoichiometric oxygen-containing composition, wherein R is a or several metals of IV. and / or V. subgroup of PSE or metals of IV. and V. and VI. or the IV. and VI. or the V. and VI. Sub-group of the PSE and one or more oxides of these metals, or mixtures of the oxides of these metals or an oxide of these metals, and x = 2 for oxides of the IV. Sub-group of the PSE, x = 2.5 for oxides of the V. sub-group of the PSE, x = 3 for oxides of VI. Subgroup of the PSE or, in the case of oxide mixtures, the sum of all x of all individual oxides, and p is the sum of the oxides and metals contained in the starting mixture.

10. The method according to claim 8, in which a molar ratio R _x : C = 1: 1 to 1: 2.95 is set to adjust a stoichiometric oxygen-containing or a substoichiometric oxygen-containing composition, wherein R is an oxide of a metal of subgroup IV of the PSE and x = 2.

11. The method according to claim 9, in which a molar ratio R _x : C = 1: 1 to 1: 2.85 is set to adjust a stoichiometric oxygen-containing or a substoichiometric oxygen-containing composition, wherein R is an oxide of a metal of subgroup IV of the PSE and x = 2.

12. The method according to claim 8, in which a molar ratio R _x : C = 1: 1 to 1: 3.45 is set to adjust a stoichiometric oxygen-containing or a substoichiometric oxygen-containing composition, wherein R is an oxide of a metal of subgroup V. of the PSE and x = 2.5.

13. The method according to claim 9, in which a molar ratio R _x : C = 1: 1 to 1: 3.35 is set to adjust a stoichiometric oxygen-containing or a substoichiometric oxygen-containing composition, wherein R is an oxide of a metal of subgroup V. of the PSE and x = 2.5.

14. Use of oxygen-containing hard materials produced according to claim 1 in a stoichiometric or substoichiometric composition in composite materials, for bearings, for indexable inserts, as an abrasive or as a magnetic head substrate.

15. Use of oxygen-containing hard materials according to claim 14, in composite materials made of oxygen-containing hard materials and oxides, in particular for a black ceramic.

16. Use of oxygen-containing hard materials according to claim 14 with an average grain size of> 5 microns for the coating of steels.