Method of manufacturing an oxidation-resistant component of a molybdenum base alloy

Abstract

The present invention relates to a method of producing a component of an Mo base alloy which is protected against high-temperature oxidation, and a correspondingly produced component. The method comprises: provision of a semifinished part composed of a Mo base alloy, provision of an Si-containing slip or of a Si-containing powder, application of the slip to the semifinished part and diffusion annealing of the semifinished part together with the applied slip to form a Si-containing outer layer or transfer of at least part of the silicon present in the powder via the gas phase to the semifinished part by means of a diffusion heat treatment of the semifinished part together with the Si-containing powder which is arranged at a distance from the semifinished part.

1 .- 13 . (canceled) 
     
     
         14 . A method of producing a component of a Mo base alloy which is protected against high-temperature oxidation, wherein the method comprises:
 provision of a semifinished part composed of a Mo base alloy,   provision of a Si-containing slip which comprises powder of at least one of Mo, W, B, Ta, Cr, Fe, Ti and alloys thereof or of a Si-containing powder which comprises a mixture of Si and Al 2 O 3  powders,   (a) application of the slip to the semifinished part and diffusion annealing of the semifinished part together with the applied slip to form a Si-containing outer layer or   (b) transfer of at least part of the silicon present in the powder via a gas phase to the semifinished part by a diffusion heat treatment of the semifinished part together with the Si-containing powder which is arranged at a distance from the semifinished part but in a vicinity of the semifinished part.   
     
     
         15 . The method of  claim 14 , wherein a molybdenum silicide or molybdenum disilicide layer is formed on at least part of the surface of the component as a result of the diffusion annealing or the diffusion heat treatment. 
     
     
         16 . The method of  claim 14 , wherein after the diffusion annealing or the diffusion heat treatment conditioning of the component by a high-temperature oxidation at a temperature above 900° C. is carried out. 
     
     
         17 . The method of  claim 16 , wherein the conditioning is carried out at a temperature of from 1000° C. to 1400° C. for from 2 hours to 100 hours. 
     
     
         18 . The method of  claim 14 , alternative (b), wherein the powder for transferring the silicon via the gas phase comprises one or more halogens. 
     
     
         19 . The method of  claim 18 , wherein the powder comprises one or more of NH 4 F, NH 4 Cl, and NaF. 
     
     
         20 . The method of  claim 14 , alternative (b), wherein the powder for transferring the silicon via the gas phase is arranged in a vessel underneath the semifinished part. 
     
     
         21 . The method of  claim 14 , alternative (b), wherein the diffusion heat treatment is carried out at a temperature above 900° C. 
     
     
         22 . The method of  claim 21 , wherein the diffusion heat treatment is carried out at a temperature of from 1000° C. to 1300° C., with a hold time at the temperature of from 0.5 to 5 hours. 
     
     
         23 . The method of  claim 21 , wherein the diffusion heat treatment is carried out under a protective gas atmosphere. 
     
     
         24 . The method of  claim 14 , alternative (a), wherein the slip comprises Si powder or Si-containing powder, a solvent and a binder. 
     
     
         25 . The method of  claim 24 , wherein the binder comprises a polyvinyl alcohol and/or a resin. 
     
     
         26 . The method of  claim 14 , alternative (a), wherein the slip comprises powder of at least one of aluminum oxide, zirconium oxide, yttrium oxide, hafnium oxide, neodymium oxide, silicon carbide, silicon nitride. 
     
     
         27 . The method of  claim 14 , alternative (a), wherein the slip comprises powder particles having an average or maximum particle size of from 0.5 to 100 μm. 
     
     
         28 . The method of  claim 14 , alternative (a), wherein the slip is applied by dipping the semifinished part into the slip, spraying the slip onto the semifinished part or printing the slip onto the semifinished part. 
     
     
         29 . The method of  claim 14 , alternative (a), wherein the slip is applied by onto the semifinished part by screen printing or template printing. 
     
     
         30 . The method of  claim 14 , alternative (a), wherein the diffusion annealing is carried out at a temperature above 900° C. 
     
     
         31 . The method of  claim 30 , wherein the diffusion annealing is carried out at a temperature of from 1000° C. and 1400° C., with a hold time at the temperature of from 1 minute to 3 hours. 
     
     
         32 . A component of a Mo base alloy which is protected against high-temperature oxidation, wherein the component is produced by the method of  claim 14 . 
     
     
         33 . The component of  claim 32 , wherein the component is a component of a turbomachine.