Diffusion barrier and protective coating for turbine engine component and method for forming

Abstract

A turbine engine component comprising a substrate made of a nickel-base or cobalt-base superalloy, a non-metallic oxide or nitride diffusion barrier layer overlying the substrate, and a protective coating overlying the barrier layer, the protective coating comprising at least one platinum group metal selected from the group consisting of platinum, palladium, rhodium, ruthenium and iridium. The diffusion barrier layer may be a deposited or thermally grown oxide material, especially aluminum oxide. The protective coating may be heat treated to increase homogeneity of the coating and adherence with the substrate. The component typically further comprises a ceramic thermal barrier coating overlying the protective coating. Also disclosed are methods for forming a protective coating system on the turbine engine component by forming the non-metallic oxide or nitride diffusion barrier layer on the substrate and then depositing the platinum group metal on top of the barrier layer.

1 . A method for forming a protective coating system on a turbine engine component, the method comprising: 
 a) providing a substrate made of a nickel-base or cobalt-base superalloy;    b) forming a non-metallic oxide or nitride diffusion barrier layer on the substrate; and    c) depositing a protective coating comprising at least two platinum group metals selected from the group consisting of platinum, palladium, rhodium, ruthenium and iridium on the barrier layer, said protective coating comprising at least about 40% by weight of platinum or rhodium, or mixtures thereof.    
     
     
         2 . The method of  claim 1  wherein the diffusion barrier layer is a thermally grown oxide material.  
     
     
         3 . The method of  claim 2  wherein the thermally grown oxide layer is promoted by depositing a layer of aluminum, aluminide, chromide, or platinum group metal on the substrate, followed by an oxidation step.  
     
     
         4 . The method of  claim 3  wherein the diffusion barrier layer is aluminum oxide having a thickness of from about 0.05 to about 10 microns.  
     
     
         5 . The method of  claim 1  wherein the substrate surface is roughened by grit blasting, etching, peening, grooving, or combinations thereof, prior to forming the diffusion barrier layer by a low pressure plasma spray, air plasma spray or high velocity oxy-fuel process.  
     
     
         6 . The method of  claim 1  wherein the diffusion barrier layer is aluminum oxide having a thickness of from about 0.5 to about 5 microns.  
     
     
         7 . The method of  claim 6  wherein the protective coating has a thickness of from about 10 to about 60 microns.  
     
     
         8 . The method of  claim 6  wherein the protective coating comprises at least about 50% by weight of platinum or rhodium, or mixtures thereof.  
     
     
         9 . The method of  claim 8  wherein the protective coating comprises at least three metals selected from the group consisting of platinum, palladium, rhodium, ruthenium, and iridium.  
     
     
         10 . The method of  claim 9  wherein the platinum group metals are sequentially deposited.  
     
     
         11 . The method of  claim 1  wherein the platinum group metal is deposited using an electroplating step.  
     
     
         12 . The method of  claim 1  wherein the platinum group metal is deposited by ion plasma deposition.  
     
     
         13 . The method of  claim 1  wherein the protective coating is heat treated at a temperature of from about 900° C. to about 1200° C. for from about 1 to about 8 hours.  
     
     
         14 . A method for forming a protective coating system on a turbine engine component, the method comprising: 
 a) providing a substrate made of a nickel-base or cobalt-base superalloy;    b) forming a non-metallic oxide or nitride diffusion barrier layer on the substrate;    c) depositing a protective coating comprising at least one platinum group metal selected from the group consisting of platinum, palladium, rhodium, ruthenium and iridium on the barrier layer; and    d) forming a ceramic thermal barrier coating over the protective coating.    
     
     
         15 . The method of  claim 14  wherein the diffusion barrier layer is a thermally grown oxide material.  
     
     
         16 . The method of  claim 15  wherein the thermally grown oxide layer is promoted by depositing a layer of aluminum, aluminide, chromide, or platinum group metal on the substrate, followed by an oxidation step.  
     
     
         17 . The method of  claim 14  wherein the diffusion barrier layer is aluminum oxide having a thickness of from about 0.05 to about 10 microns.  
     
     
         18 . The method of  claim 17  wherein the protective coating comprises at least two metals selected from the group consisting of platinum, palladium, rhodium, ruthenium and iridium.  
     
     
         19 . The method of  claim 18  wherein the protective coating has a thickness of from about 10 to about 60 microns, and comprises at least about 50% by weight of platinum or rhodium, or mixtures thereof.  
     
     
         20 . A method for forming a protective coating system on a turbine engine component, the method comprising: 
 a) providing a substrate made of a nickel-base or cobalt-base superalloy;    b) forming a non-metallic oxide or nitride diffusion barrier layer on the substrate;    c) depositing a protective coating comprising at least about 40% by weight of a platinum group metal selected from the group consisting of platinum, palladium, rhodium, ruthenium and iridium, and mixtures thereof, on the barrier layer; and    d) forming a ceramic thermal barrier coating over the protective coating.