Corrosion-resistant layered coatings

Abstract

In general, the present invention provides coating systems and processes for applying a selected coating system on a metallic substrate. The coating system includes two or more coating layers. A first layer comprises a MCrAl(Y, Hf)-type coating. The MCrAl(Y, Hf) coating is overlaid with a second coating composition that includes a metallic composition different from the MCrAl(Y, Hf) coating composition and includes one or more of: a platinum, silicon containing composition; a platinum, silicon, aluminum containing composition; a platinum, silicon, chromium containing composition; an aluminum, silicon containing composition; and an aluminum, silicon, chromium containing composition; each optionally combined with one or more of chromium, hafnium, lanthanum, manganese, yttrium and mixtures of these metals. Additionally the platinum in the metallic compositions can be exchanged in whole or in part by another noble metal. The resulting coating composition is subsequently heat treated to provide a diffused multilayer corrosion-resistant coating.

1 - 36 . (canceled) 
     
     
         37 . A method of preparing a diffused coating on a metallic article, said method comprising the steps of:
 coating the metallic article substrate with a first layer comprising an MCrAl(Y, Hf) alloy, wherein M is selected from the group consisting of: Co, Ni, Fe and mixtures thereof;   electrophoretically depositing a second layer composition over the first layer, in a single step, said second layer composition comprising platinum, silicon, chromium and aluminum; and   heat treating the coated metallic article to provide a diffused coating on the metallic article.   
     
     
         38 - 41 . (canceled) 
     
     
         42 . The method of  claim 37  and further comprising depositing an aluminide or noble metal aluminide third layer over the diffused coating, wherein the noble metal is selected from the group consisting of: platinum, palladium, ruthenium, rhodium, and mixtures or alloys thereof; 
     
     
         43 . A method of preparing a diffused coating on a metallic substrate, said method comprising the steps of:
 coating the metallic substrate with a first layer comprising an MCrAl(Y, Hf) alloy, wherein M is selected from the group consisting of: Co, Ni, Fe and mixtures thereof; and   electrophoretically depositing a second layer over the first layer, in a single step, said second layer comprising a metallic composition different from the MCrAL(Y, Hf) alloy, and wherein the metallic composition comprises a noble metal selected from the group consisting of: platinum, palladium, ruthenium, rhodium, and mixtures or alloys thereof; and one or more of Si, Al, or Co powders; and one or more of the metals selected from the group consisting of: hafnium, lanthanum, manganese, and yttrium; and   heat treating the coated metallic article to provide a diffused coating on the metallic article.   
     
     
         44 - 46 . (canceled)