WO1998021147A9

WO1998021147A9 - Method for producing oxygen-containing hard materials and their use

Info

Publication number: WO1998021147A9
Application number: PCT/EP1997/006137
Authority: WO
Filing date: 1997-11-06
Publication date: 1998-08-27

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 preparation of oxygenated hard materials and their use

Technical area

The invention relates to the field of ceramics and hard metals and relates to a process for the production of oxygenated hard materials used in composite materials, e.g. can be used 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 the production of 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 spherical type (US 5,417,952, US 5,380,688) and / or with narrow particle 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 method relates to the direct carburization / nitration of the metals and their hydrides. This process has the disadvantage that its process is very difficult and this also leads to a strong agglomeration of the reaction products. To destroy the agglomerates are long times the

ADJUSTED SHEET (RULE 91) Grinding necessary. In addition, the metallic starting materials to be used are relatively expensive.

As a second method, deposition processes such as e.g. CVD known, which are used essentially for surface coating. Occasionally oxide-containing titanium layers have become known in the coating of the hard metals (EP 537 741, JP 02057616, JP 02015159, JP 01197364, JP 61272343, JP 53-60808). By means of these oxide-containing layers, the oxidation resistance, hardness and abrasion resistance of cutting tools is increased. Larger amounts of hard materials can not be produced by this method.

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

EP 693 456 discloses a process for the production of 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. Subsequently, the reaction space is evacuated and the reaction mixture is then repeatedly flooded at a pressure of 5 to 100 kPa and temperatures between 2000 and 2400 ° C with nitrogen-containing atmosphere and evacuated again.

The composition of this powder is at 11, 7% C _ges; <0.05% Cf _re j; 9.1% N; 0.12% 0 indicated. From this a stoichiometry of x + y + z = 0.986 (with x = 0.589, y = 0.393, z = 0.0045) can be calculated.

Due to the very long holding times of the synthesis (4-5 h) and subsequent repeated evacuation and flooding, the production becomes coarser, more spherical Carbonitride powder described The reaction products were cool after cooling in an Attntor with hard metal balls wet (in gasoline) 30 min It is assumed that the distribution of the grain sizes, which according to the definition given there has a narrow Komgroßenbereich when the values between d _| o and dgo are less than 20 microns, due to the very long meals in Attntor be achieved Information on the grain distributions were not made at the same time, however, is assumed that a spherical grain shape is not achieved by the long meals, but rather a powder with late -angular grain shape and optionally produced with a broad grain spectrum The average grain sizes egen in a range> 2 microns, preferably> 3 microns

The disadvantage of this method is essentially given by the fact that a stochiometπsche composition is to be achieved, the oxygen content in the hard material as low as <0.5% by weight should take such an oxygen content leads in the conversion into stochiometπsche information to an z value of not more than 0.05, the stoichiometric composition is achieved essentially by the long synthesis times and the high temperatures used in this process

No. 5,417,952 describes a process in which titanium dioxide powder of very small grain size is coated by means of a carbon-containing atmosphere in the temperature range 200 ° C. to 1000 ° C. In a second step, the nitrogen is released under nitrogen-emitting atmosphere at temperatures between 1200 ° C. and 1600 ° C. and nitrogen incorporated and a stochiometπsches Carbonitπd TιC _x N _v with x + y = 1 and x> 0 and y <1 generated The grain sizes produced by this method are in a range of 0.05 .mu.m to 0.2 .mu.m

For the production of very finely divided, oxygen-free hard material powder, a process in US 5,380,688 is given, the heating rates in the carbothermic reduction, which ranges between 100 K / s and 100 000 000 K / s and can be achieved only in a dedicated reactor Here, oxides of 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 retention times in the reaction space required for the carbothermic reductions depending on carried out reduction in the time range of 0.2 s to 0.5 h for the carbothermic reduction Titanium oxide requires a mean hold time of 2 min to 2.75 mm and temperatures of 1550 ° C to 1950 ° C, resulting in stoichiometric TiC

US Pat. No. 5,314,656 describes a process for the preparation of TICQ _, 5NO 5, which is characterized by two successive steps. In the first step, a substoichiometric carbide TιCo _: 5 is produced, which in nitrogen-containing atmosphere is converted in a second step into a stochiometric carbonitride (x + y In this case, the transition metal (titanium in the example) is mixed with carbon in a molar ratio of 2 1 and reacted in a nitrogen-containing atmosphere by means of self-propagating high-temperature synthesis (SHS) The proof of the composition of the cubic phase (sub-stochiometric TICQ 5) was determined by the determination of the lattice parameter Determination of the composition over the lattice parameter of the cubic phase is an inadequate method. Secured conclusions about the composition of the cubic phase can only be obtained from the chemical analysis

DD 287 959 describes the formation of oxygen-poor coarse substoichiometric carbides which coarsen at temperatures above 2000 ° C. Subsequently, at temperatures of <2000 ° C. and a nitrogen-containing atmosphere, carbonitrides with a composition MeC _x N _v with y> 0.1 and x + y> 0.7. Overall, the method is directed to achieving stoichiometric or stoichiometric compositions, with intermediate sub stoichiometry being accepted in the process. This can also be taken from the specified embodiments.

It is known that for physicochemical investigations in the pseudotemonic system TiC - TiN - TiO such materials were prepared from the individual components. In this case, the TiO was prepared in an additional synthesis step from T1O2 and Ti (Mh. Chemie, 103 [4], 1972, 1130-1137; Zh. Prikl. Khim. 44 [7] 1971, 1646-1648). Elsewhere, for the synthesis in the Ti-C-0 system, a slightly oxygen-contaminated titanium carbide, non-synthesized TiO 2, and metallic titanium were used (Izv Akad Nauk SSSR, Neorg., Mater. 6 [8], 1970, 1405-1408 ).

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

The disadvantage of the known methods is that as oxygen-free as possible stoichiometric composition of hard materials were prepared which can reduce the higher levels of free carbon only by long holding times, high synthesis temperatures or by further reactions. Presentation of the invention

The object of the invention is to provide a simple process for the production of oxygen-containing hard materials in stoichiometric and substoichiometric composition.

The object is achieved by the invention specified in the claims.

In the method according to the invention for the production of oxygen-containing hard materials in a stoichiometric or substoichiometric composition, an oxide of the metals of the IV. And V. subgroup of the PSE, or mixtures of the oxides of the metals of IV., V. and VI. Subgroup of the PSE, or one or more 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. Subgroup 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, wherein a molar ratio corresponding to the stoichiometric composition Me (C _x NyO _z ) with x + y + z "1 and z> 0.1 and Me = metals of the IV and / or V. Subgroup of PSE or 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 _y 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. 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 at discontinuous heating in the respective stages between 1 min and 5 h, and the powder mixture then or in discontinuous heating after one or several holding times is cooled to room temperature. Advantageously, in the method according to the invention an inert and / or nitrogen-containing and / or hydrogen-containing and / or carbon-containing and / or another reducing atmosphere is set as the atmosphere or a vacuum during heating and / or during the holding time and / or during cooling.

Particular advantages arise when the powder mixture is heated after grinding first in a reducing atmosphere to a temperature between 1150 ° C and 1600 ° C, then held at this temperature for 1 h and then cooled to room temperature, and then this powder mixture in 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 the powder mixture is first heated after milling in a reducing or inert atmosphere to a temperature up to 2000 ° C, then held at this temperature for 3 h and then this powder mixture in a vacuum 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 weight is used as the carbon.

Particular advantages arise when the carbon is a carbon with a proportion of oxygen in the range of 5 to 20 wt .-% is used.

Advantages also result if a molar ratio R _x : C = 1: 1 to 1: (x + p) is realized for adjusting a stoichiometric oxygen-containing or a substoichiometric oxygen-containing composition, where R

7

ADJUSTED SHEET RULE 91 one or more metals of the IV., and / or V. subgroup of the PSE or metals of the

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 VI. Subgroup of the PSE or in oxide mixtures is the sum of all x of all individual oxides, and p is the sum of the oxides and metals contained in the starting mixture.

Likewise, there are advantages if a molar ratio R _x : C = 1: 1 to 1: (x + p-0.05) is set to adjust a stoichiometric oxygen-containing or 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 VI. Subgroup of the PSE or in oxide mixtures is 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 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, wherein R is one or more metals of IV. , and / or V. subgroup of the PSE or metals of the IV

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 VI. Subgroup of the PSE or in oxide mixtures is 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 also advantageous if for adjusting a stoichiometric oxygen-containing or a stoichiometric oxygen-containing

Composition a molar ratio R _x : C = 1: 1 to 1: 2.95 is realized, wherein

R is an oxide of a metal of the IV. Subgroup of the PSE and x = 2.

Particular advantages arise when setting a stoichiometric oxygen-containing or a stoichiometric oxygen-containing

Composition a molar ratio R _x : C = 1: 1 to 1: 2.85 is realized, wherein

R is an oxide of a metal of the IV. Subgroup of the PSE and x = 2.

It is also advantageous if, for adjusting a stoichiometric oxygen-containing or a substoichiometric oxygen-containing composition

Molar ratio R _x : C = 1: 1 to 1: 3.45 is realized, wherein

R is an oxide of a metal of the 5th subgroup of the PSE and x = 2.5.

Again, there are particular advantages, if for setting a stoichiometric oxygen-containing or a stoichiometric oxygen-containing composition, a molar ratio R _x : C = 1: 1 to 1: 3.35 is realized, where R is an oxide of a metal of the V. subgroup 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, indexable inserts, as abrasives or as magnetic head substrate.

Advantageously, the oxygen-containing hard materials are used in composite materials of oxygen-containing hard materials and oxides, in particular for a black ceramic.

ADJUSTED SHEET (RULE 91) It is likewise advantageous if oxygen-containing hard materials according to claim 12 having an average particle size of> 5 μm are used for coating steels.

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

Since it has hitherto generally been assumed that the use of hard materials with higher oxygen contents in composite materials causes a pronounced deterioration of the properties, it was surprising that this did not occur when using the oxygen-containing hard materials according to the invention. On the contrary, it has been shown that the properties have not only not gotten worse, but they have partly improved and there are other benefits.

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

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

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

With regard to the problem of Unterstöchiometrie in the production of hard materials by carbothermic reduction is to say that it was surprisingly found in our own experiments that the carbon content in the resulting hard material first levels to a certain level, while the oxycarbide produced loses more and more oxygen. Thus, it forms a sub-stoichiometry whose size depends on the temperature, time, pressure and atmosphere. During this process period, therefore, in the resulting cubic hard material, carbon and oxygen are not exchanged in the ratio 1 1. This means that the carbothermal reduction can be conducted to produce an oxygen-containing hard material having a desired stoichiometry or sub-stoichiometry by stopping the reduction at a certain point in time. At which point in time which substoichiometry has been reached, the person skilled in the art can readily derive from the known reaction equations.

Surprisingly, such oxygenated hard materials produced according to the invention, when used in, for example, sintered ceramics, not only cause no deterioration in properties, as would have been expected according to the general expert opinion, but in some cases even improvements in the properties.

For the production of fine-grained hard material powder, in particular <2 .mu.m, a two-stage process is used. In the first process step, the starting powder mixture is heated after grinding in a reducing atmosphere to a temperature between 1150 ° C and 1600 ° C and held there for 1 h. Subsequently, this powder mixture is heated in a vacuum to a temperature between 1350 ° C and 1800 ° C, held until 2 h and then cooled to room temperature. This results in a very fine-grained hard material powder with a comparatively high oxygen content and low free carbon content.

By varying 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 final product is advantageously influenced and reduced overall.

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

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

In the following, the invention will be explained in more detail with reference to several exemplary embodiments.

example 1

216 g of TiO 2 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 about 10 mm) with a mass ratio of 1 5. Die

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

By this method, an oxygen-containing hard powder of the composition

i, which has 0.12 mass% free carbon and a surface area (BET) of 0.97 m ² / g. The average particle size is 4.1 μm. Example 2

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

By this method, an oxygen-containing hard powder of composition TiCrj 62 ^ 0 37 was formed, which has 0.07 wt .-% free carbon and a surface (BET) of 3.0 m ² / g.

Example 3

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

By this method, an oxygen-containing hard powder of composition TiCn 60 ^ 0 30 was formed, which has 0.07 wt .-% free carbon and a surface (BET) of 1, 5 m ² / g. The average particle size is 1.75 μm (d _{1 5 9} o _{/ o} = 0.24 μm, d _{84 1} o _{/ o} = 7.47 μm).

Example 4

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

By this method, an oxygen-containing hard powder of the composition (Ti.WJCojgOo g was formed which has 0.1 mass% of free carbon and has a surface area (BET) of 2.0 m / g. Example 5

166.1 g of ZrO2 and 179.2 g of Nb2θs and 104.7 g of carbon black, which corresponds to a molar ratio of 1: 6.45 (x = 4.5, p = 2), are homogenized in a roller mixer. Subsequently, a 15-hour dry grinding in a ball mill in stainless steel containers and with hard metal balls (diameter about 10 mm) with a mass ratio of 1: 5. The temperature treatment is carried out in a furnace with graphite heating elements with stuffed into Graphittiegeln subsets of 20 g. With a heating rate of 50 K / min, the furnace is heated to a temperature of 1700 ° C. During heating, the furnace is flowed through with 100 l / h of hydrogen. This temperature is maintained for 120 minutes and then cooled in the cooling chamber, the samples. Thereafter, the samples are 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 hold time is 6 x 10 " ⁵ MPa.

By this method, an oxygen-containing hard material powder of the composition (Zr, Nb) Co _ι 83θθ, 15 formed which has 0.09 wt .-% free carbon and a surface (BET) of 1, 0 m ² / g.

Claims

claims

1. A process for the preparation 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 IV., V. and VI. Subgroup of the PSE, or one or more 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. Subgroup 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 Me (C _x N _y O _z ) with x + y + z "1 and z> 0.1 and Me = metals of the IV. or V. Subgroup of PSE or IV. and V. and VI. or the IV. and VI. or the V. and VI. Subgroup of the PSE, or according to the stoichiometric composition

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. 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 at discontinuous heating in the respective stages between 1 min and 5 h, and the powder mixture then or in discontinuous heating after one or several holding times is cooled to room temperature.

2. The method of claim 1, wherein an inert and / or nitrogen-containing and / or hydrogen-containing and / or carbonaceous and / or another reducing atmosphere is set as the atmosphere or a vacuum during heating and / or during the holding time and / or cooling ,

3. The method of claim 1 and 2, wherein the powder mixture after grinding first in a reducing atmosphere to a temperature between 1150 ° C and 1600 ° C, where it is held for 1 h and then cooled to room temperature, and then heated this powder mixture 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 of claim 1 and 2, wherein the powder mixture is heated after grinding first in a reducing or inert atmosphere to a temperature of 2000 ° C and held there for 3 h, and then this powder mixture in a vacuum 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 of claim 1, wherein the carbon used is a carbon with a proportion of oxygen in the range of 0.1 to 25 wt .-%.

6. The method according to claim 5, wherein the carbon is a carbon with a proportion of oxygen in the range of 5 to 20 wt .-% is used.

7. The method of claim 5 and 6, wherein for adjusting a stoichiometric oxygen-containing or a stoichiometric oxygen-containing composition, a molar ratio R _x : C = 1: 1 to 1: x + p is set, wherein 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 VI. Subgroup of the PSE or in oxide mixtures is 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 of claim 5 and 6, wherein for adjusting a stoichiometric oxygen-containing or a substoichiometric oxygen-containing composition, a molar ratio R _x : C = 1: 1 to 1: (x + p-0.05) is set, wherein R is an or several metals of the IV., and / or V. subgroup of the 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 VI. Subgroup of the PSE or in oxide mixtures is 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 of claim 5 and 6, wherein for adjusting a stoichiometric oxygen-containing or a substoichiometric oxygen-containing composition, a molar ratio R _x : C = 1: 1 to 1: (x + p-0.15) is set, wherein R is an or several metals of the IV., and / or V. subgroup of the 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 VI. Subgroup of the PSE or in oxide mixtures is 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 of claim 8, wherein for adjusting a stoichiometric oxygen-containing or a stoichiometric oxygen-containing composition, a molar ratio R _x : C = 1: 1 to 1: 2.95 is set, wherein R is an oxide of a metal of the IV. Subgroup of the PSE and x = 2.

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

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

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

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

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

16. Use of oxygenated hard materials according to claim 14 with a mean particle size of> 5 microns for coating steels.