WO2000078693A2

WO2000078693A2 - Utilization of a coating provided with fiber-reinforced ceramic material and methods for producing the same

Info

Publication number: WO2000078693A2
Application number: PCT/EP2000/005555
Authority: WO
Inventors: zur Förderung der angewandten Forschung e.V. Fraunhofer-Gesellschaft
Original assignee: Hirsch, Kurt; Kaiser, Mathias; Greiner, Axel; Bill, Joachim; Aldinger, Fritz
Priority date: 1999-06-19
Filing date: 2000-06-16
Publication date: 2000-12-28
Also published as: DE19928173A1

Abstract

The invention relates to the utilization of a coating which is provided with fiber-reinforced ceramic material and which has an additional coating comprised of oxides and/or nitrides and/or of mixed compounds consisting of oxides and nitrides (oxynitrides) of at least one chemical element contained in the ceramic material, especially silicon and carbon. The additional layer serves as a wear protective layer for reducing the wear on surfaces which are subjected to high levels of thermal or oxidative stress, especially inner linings of ovens and oven doors, heat shields on missiles, or the like. By using such a wear protective layer, the wear and the erosion of the fiber-reinforced ceramic material is substantially reduced at the onset of a thermally oxidative stress which, for example, occurs when opening a hot oven door or when a space missile enters the earth atmosphere. The invention also relates to methods for producing such a coating.

Description

Use of a fiber-reinforced ceramic coating and process for its manufacture

The invention relates to the use of a coating with ceramics with high strength, which contains a further layer of nitrides and / or oxides and / or mixed compounds of oxides and nitrides (oxynitrides) of at least one chemical element contained in the ceramic.

In many areas, technical components on their surface must be protected against high thermal loads, e.g. in the aerospace industry for space reentry objects, high-speed missiles, high-temperature propulsion systems for rockets or supersonic engines, in fire and disaster control technology, e.g. with immobile objects as well as with mobile fire fighting, rescue and clearing vehicles, or in the industrial area, e.g. for high temperature resistant furnaces and reactors. Such components are protected from heat by cladding or coatings, and those made of fiber-reinforced ceramic have proven particularly useful. The latter usually consists of silicon carbide ceramic reinforced with carbon fibers or of polymers, in particular polytetrafluoroethylene (US Pat. No. 4,016,322), which are carbonized when exposed to temperature.

Carbon fiber reinforced silicon carbide ceramic is characterized on the one hand by its high temperature resistance, where in the so-called rhombohedral-hexagonal high-temperature modification (α-SiC) dissociates at about 2300 ° C. On the other hand, silicon carbide ceramics have a high hardness (Mohs hardness «9.6) and consequently a high strength and a high density (D« 3.2 g / cm ³ ). Ceramic heat shields, for example for space reentry bodies, are often formed from several insulating tiles, which consist of a plate-shaped carrier and a layer of fiber-reinforced ceramic applied thereon and are applied to the reentry body to form a closed surface (DE 195 13 906).

To improve the properties of fiber-reinforced ceramics, it is known to coat the reinforcing fibers, in particular carbon fibers, with metal oxides, the

The proportion of fibers coated in this way can be up to 55% by volume, based on the total volume of the fiber-reinforced ceramic (US Pat. No. 4,962,070).

Furthermore, heat shields with a layered structure of ceramic layers arranged between metallic foils are known. US 4 925 134 describes such a structure, wherein ceramic fibers made of aluminum oxide and silicon dioxide are arranged between several metal foils. US Pat. No. 4,877,689 shows a heat protection surface with ceramic layers of silicon carbide arranged between nickel, chromium and aluminum foils.

With high thermal and oxidative loading of fiber-reinforced ceramics, such as occurs, for example, when the door of a high-temperature furnace is opened or when spacecraft enter the earth's atmosphere, such heat protection ^surfaces tend to burn up and thus erode by being oxidized and / or Sublimation slow be removed.

DE 37 83 520 T2 describes a ceramic sintered body reinforced with whiskers for use in engine parts, heat exchangers, cutting tools, ball bearings and as inert biomaterials. The main component of the ceramic matrix of the sintered body is either a ceramic oxide or a mixture of a ceramic oxide with at least one substance from the group consisting of hard carbides, nitrides and borides. The ceramic whiskers also consist of nitrides, carbides and / or oxides, such as TiN, TiC, B ₄ C, A1 ₂ 0 ₃ , Zr0 ₂ , SiC, Si ₃ N. In order to increase the wear resistance, corrosion resistance and in particular the fracture toughness of such composite materials reinforced with whiskers, it is provided on the one hand that the whiskers are coated with a thin, maximum 0.1 μm thick surface layer of a chemically more resistant material than the whisker material, on the other hand a 0.05 to 20 μm thick coating layer of the chemically more resistant material, in particular A1 ₂ 0 ₃ , TiN or TiC, is applied to the ceramic sintered body.

DE 43 29 551 AI is a method for producing high-temperature resistant reflectors, mirrors, antennas or the like, in particular for orbital use, can be removed, objects of this type having a surface-smoothing, reflective layer made of silicon or silicon carbide, carbon, silicon oxide, silicon nitride or from Gold, silver, nickel, copper or alloys thereof are applied by physical vapor deposition (PVD), chemical vapor deposition (CVD) or flame spraying. The objects in turn have a support structure made of fiber-reinforced materials, such as carbon-fiber-reinforced carbon, carbon-fiber-reinforced silicon carbide, silicon carbide-fiber-reinforced silicon carbide or mixtures of such materials. The coating of these objects, which are generally used only once, is used exclusively to optimize the electromagnetic properties and is therefore referred to as a reflection layer. It is used in particular to achieve a high level of mirror component rigidity, whereby primarily large-area and three-dimensional mirror structures are to be achieved.

The object of the invention is to propose a new use for a coating of the type mentioned at the beginning. It is also directed to methods for producing such a coating.

According to the invention, this object is achieved when using a coating of the type mentioned at the outset in that the further layer serves as a wear protection layer to reduce the erosion on surfaces which are subjected to high thermal and / or oxidative loads.

Surprisingly, it has been found that the nitrides, oxides or oxynitrides of at least one wear protection layer contained in the ceramic protect the fiber-reinforced ceramic against oxidation and sublimation and thus against erosion and erosion by essentially protecting it from contact with oxygen or Nitrogen is preserved both in atomic and in particular in molecular form, on the other hand, by largely inhibiting oxidation of the ceramic with oxygen or nitrogen, which also releases heat of reaction, ensures lower thermal stress and thus higher thermal fatigue strength. In this way, it becomes possible, in particular, to use expensive, multi-use objects with a heat protection surface or cladding made of fiber-reinforced ceramic, for example rockets, manned spacecraft, To provide high-temperature reactors and high-temperature furnaces, such as melting furnaces and in particular furnace doors, etc., in a simple and inexpensive manner, perfect heat protection while protecting the fiber-reinforced ceramic provided for this purpose.

The mode of operation of the wear protection layer used to reduce the erosion and erosion of the ceramic is explained below:

When thermal and oxidative stressing of ceramic surfaces of the aforementioned type occurs, thermal stress begins, e.g. immediately when a spacecraft enters the earth's atmosphere or when the door of a high-temperature furnace is opened

Erosion, as long as the concentration of the atmospheric gases relevant for the oxidative attack (0 ₂ , N ₂ ) on the surface is greatest or as long as the concentration of the reaction products formed on the surface is still low. By sublimation and oxidation of the fiber-reinforced ceramic, solid and gaseous reaction products such as CN, SiO, Si, CO, C0 ₂ etc. are generally formed under the prevailing conditions, so that an increased concentration of these reaction products is established directly on the surface which counteract further oxidation on the surface by the atmospheric gases. The gases must first diffuse through the reaction products in order to react with the fiber-reinforced ceramic in deeper layers. This results in a chemical that depends on the kinetics

Balance one. The nitrides, oxides and / or oxynitrides of at least one wear protection layer containing a chemical element contained in the ceramic or also consisting entirely of at least one of the substances mentioned ensures in particular at the beginning of the thermally oxidative stress. to reduce the erosion and erosion of the fiber-reinforced ceramic, since the reaction products which usually only form during the oxidative attack of the ceramic and which inhibit the oxidation are already present in the wear protection layer and do not have to be released by oxidation of the fiber-reinforced ceramic that the ceramic is largely protected from erosion and erosion at the beginning of the load and only after the wear protection layer has been removed, after the chemical equilibrium, which is dependent on the kinetics, has already been established and the inhibiting substances of the wear protection layer are formed anew by oxidation of the ceramic is exposed to oxidative attack. Furthermore, the sublimation on the surface of the fiber-reinforced ceramic is largely prevented or at least reduced at the beginning of the stress, since the wear protection layer inhibits the exothermic oxidation from the beginning and therefore no additional heat of reaction is released. The wear protection layer thus anticipates the formation of a self-protection layer typical of the ceramic base material.

The wear protection layer, which can be reapplied to the fiber-reinforced ceramic to be protected, for example, before each thermal stress, considerably increases the service life of the ceramic in a simple and inexpensive manner. The wear protection layer is e.g. also suitable for surfaces which are formed by a plurality of ceramic insulating tiles which form an essentially closed surface (DE 195 13 906).

The thickness of the wear protection layer can be between 1 μm and 500 μm, in particular between approximately 10 μm and approximately 50 μm, depending on the requirements for thermal resistance. Studies have shown that layer thicknesses In the range from 1 μm to 30 μm, the erosion of the surface of the fiber-reinforced ceramic can be significantly reduced at the beginning of thermal stress.

In a preferred embodiment, fiber-reinforced, in particular carbon fiber-reinforced ceramics are used which contain at least 25% by mass of silicon carbide (SiC) and whose wear protection layer contains silicon nitrides and / or silicon oxides and / or silicon oxynitrides and / or silicon oxide carbides.

Various methods can be used to produce such a coating. The wear protection layer can thus be applied to the fiber-reinforced ceramic by means of a PVD process (physical vapor deposition) known per se. This addresses processes for the production of thin layers in which the coating material, namely nitrides and / or oxynitrides and / or oxides, is vacuum-cleaned by at least one chemical element contained in the ceramic, in particular silicon and carbon, by purely physical methods Gas phase is transferred and deposited on the surface of the fiber-reinforced ceramic to be protected. Essentially, three different process variants are possible: On the one hand, the coating material can be vapor-deposited on the surface in a high vacuum, with the transition either from the solid to the liquid to the gaseous state or directly from the solid to the gaseous state by means of electrical resistance - Parking heaters, electron or laser bombardment, arc vaporization or the like. is heated. Instead, sputtering is also possible, in which a solid target consisting of the respective coating material is atomized in a vacuum with high-energy ions, for example noble gas ions, in particular argon ions, with, for example, an ion source Noble gas plasma is used. Finally, a target consisting of the respective coating material can also be bombarded with ion beams under vacuum, converted into the gaseous state and deposited on the surface of the fiber-reinforced ceramic. Of course, the aforementioned PVD processes can also be combined, the wear protection layer being applied, for example by plasma-assisted vapor deposition.

According to a further method known per se, the wear protection layer is applied to the fiber-reinforced ceramic by means of a CVD (Chemical Vapor Deposition) method. In contrast to the PVD process, chemical reactions take place in the CVD process (gas phase separation). Here, the gas components generated at temperatures of about 200 to 2000 ° C by means of thermal, plasma, photon or laser activated gas phase deposition are mixed with an inert carrier gas, e.g. Argon, usually transferred to a reaction chamber in which the chemical reaction takes place. The educated

Solid components are deposited on the surface of the fiber-reinforced ceramic. The volatile reaction products are removed with the carrier gas.

The wear protection layer can also be applied by means of known thermal spray processes by means of jet, liquid, gas or electrical gas discharge, such as laser, melt bath, flame, detonation, high-speed, arc, plasma spraying or the like. (H.-D. Steffens, J. Wilden: "Modern Coating Process", 2nd revised edition, DGM Informationsgesellschaft, ISBN 3-88355-233-2, 1992) are applied to the fiber-reinforced ceramic, whereby they are preferably applied by means of a plasma spraying process becomes. Here, a fixed target is created by applying a high-frequency electromagnetic field combined ionization of a gas, for example air, oxygen, nitrogen, hydrogen, noble gases etc., heated by means of a plasma torch and converted into the gas phase. The target can consist, for example, of silicon nitride, oxynitride and / or oxide and can be converted physically into the gas phase and deposited on the surface of the fiber-reinforced ceramic. The target can also consist of silicon and can be deposited on the surface of the fiber-reinforced ceramic by reaction with the ionized gas - in this case oxygen and / or nitrogen - as silicon nitride, oxynitride, and / or oxide.

According to another method, it is provided that the wear protection layer is applied by plasma polymerization and subsequent thermal treatment of the plasma polymer. To generate the plasma, such solid or liquid mono-, di-, oligo- or polymers are preferably atomized by means of noble gases ionized by high-frequency energy, which have chemical elements contained in the fiber-reinforced ceramic forming the heat protection surface or cladding. If the ceramic consists in particular of silicon compounds, for example of silicon carbide, then organosilicon compounds, for example polysiloxanes, polymethylsiloxanes, hexamethyldisiloxane (HMDSO), nitrogen-containing borosiloxanes, silazanes or polysilazanes or the like. , used to generate the plasma. Other organic compounds, in particular titanium, zirconium, aluminum, are also conceivable. The monomers or monomer fragments released during the atomization repolymerize on the surface of the fiber-reinforced ceramic to form a crosslinked polymer with the formation of a firmly adhering thin layer. In the subsequent thermal treatment, which is carried out, for example, at a temperature between 700 ° C. and 1500 ° C., the polymer layer is formed with the formation of nitrides, oxynitrides and / or oxides, ceramized in particular silicon nitrides, oxynitrides and / or oxides. The thermal treatment is carried out in particular under reduced pressure and / or under an inert gas atmosphere, the polymer layer being split thermolytically or pyrolytically. In order to specifically control the formation of nitrides, oxynitrides or oxides during the thermolysis, it is preferred in a preferred embodiment that oxygen and / or nitrogen is added during the thermal treatment.

Another method provides that the wear protection layer is applied by infiltrating a polymer and / or prepolymer solution into the surface of the fiber-reinforced ceramic to be protected and then the polymer is thermally treated. For infiltration, the ceramic of the heat protection surface is e.g. slowly immersed in the polymer solution (dip coating) and infiltrated with the solution by capillary action of its pores. The layer thickness can be controlled via the immersion or extraction speed, the residence time in the solution and the viscosity of the solution. The viscosity is adjusted, for example, via the concentration of the polymer in the polymer solution, for example to infiltrate porous ceramics. a concentration of the polymer in the solvent of up to about 30% by mass is selected, while the concentration of the polymer in the solvent is preferably set up to about 10% by mass to produce crack-free layers on the ceramic surface. The polymer solution can also be infiltrated under pressure (pressure infiltration) or under vacuum (vacuum infiltration). As polymers or

The above-mentioned organosilicon compounds are also suitable for prepolymers. The thermal treatment is carried out in the manner described above. According to a further method, it is provided that the wear protection layer by infiltrating polymerizable alcoholates (alkoxides) containing functional groups of at least one chemical element contained in the ceramic into the surface of the fiber-reinforced ceramic to be protected, crosslinking the alcoholates to form polymers and subsequent thermal treatment of the polymers formed is applied to the fiber-reinforced ceramic. Such a process is known for the production of glass ceramics from metal alcoholates (V. Gottardi

(Editor): Glasses an glass ceramics from gels, Proc. Int. Workshop on Glass and Glass Ceramics from Gels, Padua 1981, in: J. Non-cryst. Solids 48, 1982). According to the invention, alcoholates of at least one chemical element contained in the ceramic, for example silicon alcoholates, are used for the wear protection layer. The optionally organically modified alcoholates applied to the surface to be protected are converted into an inorganic network, for example by controlled hydrolysis and condensation of the alcoholates. The alcoholates act as basic condensing agents. Alternatively, cocondensation can be carried out with other metal alcoholates, for example titanium, zirconium, aluminum alcoholates etc., or with organic nitrogen compounds. The polymerizable groups fixed to the organic network are then crosslinked, for example thermally or by high-frequency electromagnetic radiation, for example ultraviolet (UV). The generally inorganic / organic copolymer obtained is converted by thermal treatment to form a stable wear protection layer composed of nitrides, oxynitrides and / or oxides of the chemical elements of the alcoholates used. The thermal treatment is also carried out in the manner described above. The invention is explained in detail below on the basis of exemplary embodiments with reference to the diagrams. Show it:

Fig. 1 is a diagram of the time behavior of the

Erosion rate of a carbon fiber reinforced silicon carbide ceramic at two different surface temperatures without wear protection layer (1,2) and with an approximately 15 μm thick wear protection layer made of SiC nitrides (3) and

2 shows a diagram of the course over time of the surface temperature of a carbon fiber-reinforced silicon carbide ceramic without wear protection layer (4) and with two different wear protection layers (5, 6)

Fig.l shows the erosion rate in mg / s of a heat shield made of carbon fiber reinforced silicon carbide ceramic without a wear protection layer at 1870 K (1) and at 1950 K (2) as a function of time. At the beginning of the thermal or oxidative stress, a high erosion occurs on the heat shield due to the formation of an oxide layer on the ceramic surface and after about 30 minutes reaches an almost constant asymptotic equilibrium value (7) of about 0.16 mg / s.

2 shows the surface temperature profile of a heat shield consisting of carbon fiber reinforced silicon carbide ceramic as a function of time with experimentally simulated space reentry conditions. posed. At the beginning of the thermal or oxidative stress, the uncoated heat shield (4) has a high temperature rise to approximately 1800 ° C., which is caused, among other things, by the heat of reaction released during the surface oxidation of the ceramic. After an oxide layer has formed on the ceramic surface after about 5 minutes, the surface temperature drops to an almost constant asymptotic equilibrium value (8) of about 1600 to 1650 ° C.

As can be seen in curve 3 in FIG. 1, an approximately 15 μm thick wear protection layer of the ceramic with SiC nitrides reduces the erosion rate which increased at the beginning of the thermal or oxidative stress to a value approximately corresponding to the equilibrium value (7). so that a low, essentially constant erosion rate is obtained over the entire time of the thermal-oxidative load.

The wear protection layer can be applied, for example, by infiltrating a polymer solution into the ceramic (dip coating) and subsequent thermal treatment of the polymer applied in this way to form the nitrides.

Accordingly, the surface temperature (FIG. 2) is reduced by approximately 250 ° C. by a wear protection layer on the ceramic surface (5, 6) at the beginning of the thermal or oxidative stress. While (5) shows the temperature curve on a ceramic surface with an approximately 15 μm thick wear protection layer made of silicon oxide applied by PVD or CVD processes, (6) shows the temperature curve on a ceramic surface with a dip coating with polymethylsiloxane and subsequent Thermolysis applied wear protection layer made of silicon oxide.

Example 1:

A heat shield made of carbon fiber-reinforced silicon carbide ceramic is provided with a wear protection layer in accordance with one of the following design variants, which ensures increased temperature resistance and reduced erosion of the ceramic.

a) Thermal evaporation of silicon dioxide (Si0 ₂ ) using an electron beam evaporator (PVD process):

A quartz target (Si0 ₂ ) is vacuumed using a

Electron beam heated to sublimation of Si0 ₂ and the gaseous Si0 ₂ deposited on the surface of the ceramic heat shield. An Si0 ₂ wear protection layer with a layer thickness of about 10 to 100 μm forms on the ceramic in a short time.

b) Reactive thermal evaporation of silicon monoxide

(SiO) with the addition of oxygen and / or nitrogen (CVD process):

An SiO target is thermally evaporated in a vacuum. By adding oxygen, a wear protection layer consisting of SiO _x can be set to 1.5 ≤ x ≤ 2. By addition of nitrogen and Sauer - -Stickstoffgemische material with a variable ratio or oxynitride composed of silicon nitride wear protection layer can be applied to the ceramic ^¬ the. c) Direct sputtering of silicon dioxide (Si0 ₂ ) with argon

(PVD process):

A quartz target (Si0 ₂ ) is atomized by bombardment with argon ions in a vacuum and deposited on the ceramic. In this way, very dense layers are obtained in particular.

d) Reactive sputtering of silicon with argon (CVD process):

A silicon target is atomized by bombardment with argon ions in a vacuum. By adding oxygen and / or nitrogen in a controlled manner, wear protection layers of SiO _x with 1.5 ≤ x ≤ 2 or of silicon nitride or oxynitride are obtained.

e) Thermally activated vapor deposition from volatile silicon compounds (CVD process):

Volatile silicon compounds, eg silanes, are thermally transferred to the gas phase in a vacuum and deposited on the ceramic by controlled addition of oxygen and / or nitrogen as SiO _x with 1.5 ≤ x ≤ 2, silicon nitride or oxynitride.

f) Plasma-activated vapor deposition from volatile silicon compounds (CVD method):

Volatile silicon compounds, for example silanes or silicon-organic compounds, such as hexamethyldisiloxane (HMDSO), are converted into the gas phase in a vacuum by means of a plasma, for example an argon plasma, and by controlled addition of oxygen and / or nitrogen as SiO _x with 1.5 ≤ x <2, silicon nitride or oxini- trid deposited on the ceramic.

Example 2:

A heat shield made of carbon fiber reinforced silicon carbide ceramic is made by plasma polymerization with a plasma polymer made of an organosilicon compound, e.g. HMDSO, coated with a layer thickness of about 50 microns. With the controlled addition of oxygen and / or nitrogen, the plasma polymer is ceramized by thermolysis at about 800 ° C.

Example 3:

A heat shield consisting of liquid-phase-siliconized carbon fiber-reinforced carbon (C / C-SiC material) is desiliconized (freed from elemental silicon) and by infiltration with an organosilicon, preceramic polymer solution or mixtures of several such polymers in a solution and subsequent thermal treatment of the Coated polymer layer. For a porous ceramic, a polymer concentration in the solution of up to about 30% by mass is set. Polymethylsiloxane is selected as the preceramic polymer and a solution of 30% by mass and 5% by mass of polymethylsiloxane in ethanol is prepared in each case. The ceramic is first immersed in the 5% by mass ethanolic polymethylsiloxane solution by means of dip coating with immersion and extraction speeds of 2.7 cm / min in each case in order to obtain a crack-free wear protection layer. The ceramic coated in this way is thermolyzed in a quartz deflection tube for one hour at about 800 ° C. to ceramize the polymer layer to form silicon oxide under an argon atmosphere. The heating and cooling rate is about 1.8 K / min each. Then the ceramic is used to reduce the porosity dipped several times into the 30% by mass ethanolic polymethylsiloxane solution and the polymer layer was again pyrolyzed in the manner described. The course of the surface temperature of a ceramic coated in this way under experimentally simulated space travel re-entry conditions as a function of time is shown in curve (6) in FIG. 2.

Example 4:

A heat shield consisting of carbon fiber reinforced silicon carbide ceramic is infiltrated with organically modified silicon alcoholates (silicon alkoxides) containing polymerizable functional groups, hydrolysis and condensation of the silicon alcoholates to form an inorganic network and UV-initiated crosslinking of the polymerizable groups attached to the inorganic network with an inorganic / coated organic copolymer. The latter is ceramized according to Example 3 to form silicon oxide.

Claims

claims

1. Use of a coating with fiber-reinforced ceramic, which has a further layer of nitrides and / or oxides and / or mixed compounds of oxides and nitrides (oxynitrides) of at least one chemical element contained in the ceramic, characterized in that the further layer as Wear - protective layer to reduce the burn-off on thermally and / or oxidatively highly stressed surfaces.

2. Use of a coating according to claim 1, characterized in that the thickness of the wear protection layer is between approximately 1 µm and approximately 500 µm.

3. Use of a coating according to claim 2, characterized in that the thickness of the wear protection layer is between about 10 microns and about 50 microns.

4. Use of a coating according to one of claims 1 to 3, characterized in that the fiber-reinforced ceramic contains at least 25 mass .-% silicon carbide (SiC) and the wear protection layer silicon nitride and / or silicon oxide and / or silicon oxynitride and / or silicon oxide carbide.

5. A method for producing a coating according to one of claims 1 to 4, characterized in that the wear protection layer is applied to the fiber-reinforced ceramic by means of a PVD process (Physical Vapor Deposition).

6. A process for producing a coating according to one of claims 1 to 4, characterized in that the wear protection layer is applied to the fiber-reinforced ceramic by means of a CVD process (Chemical Vapor Deposition).

7. A method for producing a coating according to one of claims 1 to 4, characterized in that the wear protection layer by means of a thermal

Spraying process is applied to the fiber-reinforced ceramic.

8. The method according to claim 7, characterized in that the wear protection layer is applied to the fiber-reinforced ceramic by means of a plasma spraying process.

9. A method for producing a coating according to one of claims 1 to 4, characterized in that the wear protection layer is applied to the fiber-reinforced ceramic by plasma polymerization and subsequent thermal treatment of the plasma polymer.

10. A method for producing a coating according to any one of claims 1 to 4, characterized in that the wear protection layer by infiltrating a polymer and / or prepolymer solution into the surface of the fiber-reinforced ceramic to be protected and then thermal treatment of the by infiltration. brought polymer is applied to the fiber-reinforced ceramic.

11. A process for producing a coating according to one of claims 1 to 4, characterized in that the wear protection layer by infiltrating alcohols containing polymerizable functional groups from at least one chemical element contained in the ceramic into the surface to be protected fiber-reinforced ceramic, crosslinking of the alcoholates to form polymers and subsequent thermal treatment of the polymers formed is applied to the fiber-reinforced ceramic.

12. The method according to any one of claims 9 to 11, characterized in that the thermal treatment is carried out at a temperature between 700 ° C and 1500 ° C.

13. The method according to any one of claims 9 to 12, characterized in that the thermal treatment is carried out under reduced pressure.

14. The method according to any one of claims 9 to 12, characterized in that the thermal treatment is carried out under an inert gas atmosphere.

15. The method according to any one of claims 9 to 14, characterized in that oxygen and / or nitrogen is added in the thermal treatment.