LASER INDUCED, FINE GRAINED, GAMMA PHASE SURFACE FOR NiCoCrAlY COATINGS PRIOR TO CERAMIC COAT

Abstract

A process for forming a thermal barrier coating on a part comprising depositing an aluminum containing bond coat on the part, the bond coat comprising a surface; cleaning the surface to remove oxides and debris from the surface of the bond coat; forming a gamma phase layer proximate the surface of the bond coat; forming an aluminum oxide layer on the surface of the bond coat; and depositing a ceramic topcoat on the aluminum oxide layer on the bond coat.

What is claimed is: 
     
         1 . A process for forming a thermal barrier coating on a part comprising:
 depositing an aluminum containing bond coat on the part, said bond coat comprising a surface;   cleaning said surface to remove oxides and debris from the surface of the bond coat;   forming a gamma phase layer proximate the surface of the bond coat;   forming an aluminum oxide layer on said surface of said bond coat; and   depositing a ceramic topcoat on the aluminum oxide layer on the bond coat.   
     
     
         2 . The process according to  claim 1 , wherein said cleaning comprises exposing the surface to an energy beam focused on the surface of the bond coat and forming a liquid from the bond coat proximate the surface. 
     
     
         3 . The process according to  claim 2 , further comprising:
 rapidly cooling the liquid into said gamma phase layer; and   forming an alpha aluminum oxide proximate said surface.   
     
     
         4 . The process according to  claim 2 , wherein said energy beam produces high intensity, short duration energy beam pulses. 
     
     
         5 . The process according to  claim 1 , further comprising:
 inhibiting a non-alpha aluminum oxide layer from growing responsive to said gamma phase layer proximate said surface.   
     
     
         6 . The process according to  claim 1 , further comprising:
 distributing the aluminum in the bond coat uniformly, so that the alpha aluminum oxide layer is even and has reduced internal stresses.   
     
     
         7 . The process according to  claim 1 , wherein said gamma phase layer proximate the surface comprises a supersaturated aluminum content and low aluminum diffusivity properties. 
     
     
         8 . The process according to  claim 1 , further comprising:
 growing an initial alpha-alumina scale during the cleaning step.   
     
     
         9 . The process according to  claim 1 , wherein the gamma phase layer comprises a thickness of about  1 . 5  microns. 
     
     
         10 . The process according to  claim 1 , wherein said gamma phase layer proximate the surface of the bond coat is an aluminum diffusion inhibitor. 
     
     
         11 . The process according to  claim 8 , wherein said gamma phase layer impedes fast aluminum oxidation at the surface. 
     
     
         12 . The process according to  claim 8 , wherein the gamma phase layer allows for a very thin initial alpha-alumina scale to grow during said cleaning step.