Thermo-mechanical characterizations of coatings for HP turbines

Abstract

Three different coatings were studied in this work : vacuum plasma-sprayed NiCoCrAIYTa, electrolytically deposited NiCoCrAIYTa and Ni-Pt aluminide diffusion coatings. These three coatings were deposited on AM3 single crystal alloy. The tensile properties of coated single crystal test specimens were investigated. Ductile to Brittle Transition Temperatures (DBTT) were determined from tensile tests. All the coatings were examined before and after testing. All the tested coatings induce a ductile/brittle transition. Strain rate has a great influence on the transition temperature. The comparison between plasma-sprayed deposition and electrodeposition illustrates the strong influence of coating microstructure. In every case, NiCoCrAIYTa coatings were more ductile, and then less detrimental, than aluminide coatings.