Microstructure and oxidation resistance of Pd+Zr and Pd+Hf co-doped aluminide coatings deposited on Mar-M247 nickel superalloy

Abstract

Pd+Zr and Pd+Hf co-doped aluminide coatings were deposited on the Mar-M247 nickel superalloy by the palladium electroplating followed by zirconizing-aluminizing or hafnizing-aluminizing processes. Both coatings consisted of two zones, the outer and the interdiffusion one build of the ?-(Ni,Pd)Al phase. Hafnium and zirconium formed inclusions that precipitated at the border of the zones and close to the surface (only in the Zr+Pd modified coating). Oxidation resistance of the Pd+Zr co-doped aluminide coating was significantly better than the Pd+Hf co-doped one. Hafnium content in the Pd+Hf co-doped coating could exceed the border value.