Process and device for coating silicon carbide fibers

Abstract

In a process for coating silicon carbide fibers with a titanium-based alloy by plasma spraying, the titanium-based alloy is sprayed onto the silicon carbide fibers by way of an electrode-free high-pressure plasma. The high-pressure plasma is generated in a microwave- or radiowave-transparent working tube with a gas inlet opening and a gas outlet opening by ignition of a process gas which has been introduced into the working tube at a pressure p≧1 bar. The plasma is maintained by absorption of microwaves or radiowaves and is passed into the working space as a plasma jet through a nozzle arranged at the gas outlet opening of the working tube.

I claim:  
     
         1 . A process for coating silicon carbide fibers with a titanium-based alloy by plasma spraying, the titanium-based alloy being sprayed onto the silicon carbide fibers by way of an electrode-free high-pressure plasma, comprising: 
 generating the high-pressure plasma in a microwave- or radiowave-transparent working tube with a gas inlet opening and a gas outlet opening by ignition of a process gas which has been introduced into the working tube at a pressure p≧1 bar,    maintaining the plasma by absorption of microwaves or radiowaves, and    passing the plasma into the working space as a plasma jet through a nozzle arranged at the gas outlet opening of the working tube.    
     
     
         2 . The process according to  claim 1 , wherein the process gas for generating the high-pressure plasma contains hydrogen.  
     
     
         3 . The process according to  claim 1 , wherein the titanium-based alloy is fed to the process gas in the form of a liquid precursor, a solid precursor, or both a liquid and solid precursor.  
     
     
         4 . The process according to  claim 3 , wherein the liquid precursor is titanium tetrachloride.  
     
     
         5 . The process according to  claim 3 , wherein the solid precursor is a titanium-based alloy powder.  
     
     
         6 . The process according to  claim 2 , wherein the process gas contains a mixture of hydrogen and an inert gas.  
     
     
         7 . The process according to  claim 2 , wherein the titanium-based alloy is fed to the process gas in the form of a liquid precursor, a solid precursor, or both a liquid and solid precursor.  
     
     
         8 . The process according to  claim 7 , wherein the liquid precursor is titanium tetrachloride.  
     
     
         9 . The process according to  claim 7 , wherein the solid precursor is a titanium-based alloy powder.  
     
     
         10 . A device for carrying out a process according to one of the preceding claims, comprising at least two high-pressure plasma torches, each of the high-pressure plasma torches producing one plasma jet without using electrodes, the plasma torches being arranged symmetrically with respect to one another in such a manner that the plasma jets meet at least at one point through which the silicon carbide fibers which are to be coated are guided.  
     
     
         11 . The device according to  claim 10 , wherein three of said high-pressure plasma torches are arranged in such a manner that they are at angles of 120° with respect to one another.