Coated substrates and methods of producing the same

Abstract

Coated substrates and methods of producing the same are provided. In an exemplary embodiment, a method of coating a substrate includes brazing a first bond coat layer to the substrate, where the substrate includes a ceramic material. A second bond coat layer is plasma sprayed overlying the first bond coat layer to form a composite bond coat with the first bond coat layer positioned between the second bond coat layer and the substrate. An environmental barrier coating layer is applied overlying the second bond coat layer such that the first and second bond coat layers are positioned between the substrate and the environmental barrier coating layer.

What is claimed is: 
     
         1 . A method of coating a substrate comprising:
 brazing a first bond coat layer to the substrate, wherein the substrate comprises a ceramic material;   plasma spraying a second bond coat layer overlying the first bond coat layer to form a composite bond coat, wherein the first bond coat layer is positioned between the second bond coat layer and the substrate; and   applying an environmental barrier coating layer overlying the second bond coat layer such that the first bond coat layer and the second bond coat layer are positioned between the substrate and the environmental barrier coating layer.   
     
     
         2 . The method of  claim 1  wherein brazing the first bond coat layer comprises brazing the first bond coat layer to the substrate wherein the substrate comprises a silicon based monolithic ceramic or ceramic matrix composite. 
     
     
         3 . The method of  claim 1  wherein brazing the first bond coat layer comprises brazing the first bond coat layer to the substrate wherein the substrate comprises silicon nitride. 
     
     
         4 . The method of  claim 1  wherein brazing the first bond coat layer to the substrate comprises brazing the first bond coat layer wherein the first bond coat layer comprises from about 5 mole percent to about 40 mole percent of a first additional material, wherein the first additional material comprises one or more of a metal and a silicide. 
     
     
         5 . The method of  claim 1  wherein brazing the first bond coat layer to the substrate comprises brazing the first bond coat layer wherein the first bond coat layer comprises from about 5 mole percent to about 40 mole percent of a first additional material selected from the group consisting of a transition metal silicide and combinations of transition metal silicides. 
     
     
         6 . The method of  claim 1  wherein brazing the first bond coat layer comprises brazing the first bond coat layer to the substrate wherein the first bond coat layer comprises silicon from about 60 mole percent to about 95 mole percent. 
     
     
         7 . The method of  claim 1  wherein brazing the first bond coat layer comprises brazing the first bond coat layer wherein the first bond coat layer comprises silicon and a first additional material at a eutectic point. 
     
     
         8 . The method of  claim 1  wherein brazing the first bond coat layer comprises heating the first bond coat layer and the substrate at a temperature of from about 1,300 degrees centigrade to about 1,400 degrees centigrade. 
     
     
         9 . The method of  claim 1  wherein brazing the first bond coat layer comprises heating the first bond coat layer in a brazing atmosphere free of an oxidizing agent. 
     
     
         10 . The method of  claim 1  wherein plasma spraying the second bond coat layer comprises plasma spraying the second bond coat layer overlying the first bond coat layer wherein the second bond coat layer comprises from about 60 to about 100 mole percent silicon. 
     
     
         11 . The method of  claim 1  wherein plasma spraying the second bond coat layer comprises plasma spraying the second bond coat layer wherein the second bond coat layer comprises from about 0 to about 40 mole percent of a second additional material, wherein the second additional material is selected from the group consisting of a transition metal silicide and combinations of transition metal silicides. 
     
     
         12 . The method of  claim 1  wherein plasma spraying the second bond coat layer comprises plasma spraying the second bond coat layer such that the second bond coat layer directly contacts the first bond coat layer. 
     
     
         13 . The method of  claim 1  wherein applying the environmental barrier coating layer comprises applying the environmental barrier coating layer wherein the environmental barrier coating layer comprises an oxide ceramic. 
     
     
         14 . A method of coating a substrate comprising:
 forming a composite bond coat overlying the substrate, wherein the substrate comprises a ceramic material, the composite bond coat comprises a first bond coat layer having a first surface roughness R a1 , and the composite bond coat comprises a second bond coat layer having a second surface roughness R a2  greater than the first surface roughness R a1 , and wherein surface roughness measured in R a  is an arithmetic average of an absolute value of vertical deviations from a mean line; and   applying an environmental barrier coating layer to the composite bond coat such that the composite bond coat is positioned between the substrate and the environmental barrier coating layer.   
     
     
         15 . The method of  claim 14  further comprising:
 forming the second bond coat layer with the second surface roughness R a2  that is about two or more times greater than the first surface roughness R a1  for the first bond coat layer. 
 
     
     
         16 . The method of  claim 14  wherein forming the composite bond coat comprises:
 forming the first bond coat layer in direct contact with the substrate; and 
 forming the second bond coat layer overlying the first bond coat layer. 
 
     
     
         17 . The method of  claim 14  wherein forming the composite bond coat comprises:
 brazing the first bond coat layer to the substrate; and 
 plasma spraying the second bond coat layer overlying the first bond coat layer. 
 
     
     
         18 . The method of  claim 14  wherein forming the composite bond coat comprises forming the composite bond coat overlying the substrate, wherein the substrate comprises from about 80 to about 100 weight percent of a silicon based ceramic material. 
     
     
         19 . A substrate comprising:
 a first bond coat layer overlying the substrate, wherein the substrate comprises a silicon based ceramic material, and wherein the first bond coat layer has a first surface roughness;   a second bond coat layer overlying the first bond coat layer such that the first bond coat layer is positioned between the substrate and the second bond coat layer, wherein the second bond coat layer has a second surface roughness greater than the first surface roughness; and   an environmental barrier coating layer overlying the second bond coat layer such that the first bond coat layer and the second bond coat layer are positioned between the substrate and the environmental barrier coating layer.   
     
     
         20 . The substrate of  claim 19  wherein:
 the first bond coat layer comprises from about 60 mole percent to about 95 mole percent silicon, and the first bond coat layer comprises from about 5 mole percent to about 40 mole percent of a first additional material wherein the first additional material comprises one or more of a metal and a silicide; and 
 the second bond coat layer comprises from about 60 mole percent to about 100 mole percent silicon.