Factors affecting the microstructure of platinum-modified aluminide coatings during a vapor phase aluminizing process

Platinum (Pt)-modified aluminide coatings were developed by electroplating a thin layer of Pt followed by an industrial vapor phase aluminizing process. The goal of this work was to systematically investigate the effect of critical coating process parameters (such as the electroplated Pt thicknesses, Al contents in Cr–Al nuggets, diffusion heat treatments) and substrates on the final Pt-modified aluminide coatings. Surface morphology and cross-section microstructure of the developed coatings were inspected and compared by using Optical Microscope, Scanning Electron Microscope (SEM) equipped with energy dispersive spectroscopy (EDS). Experimental results showed that the Al and/or Pt increase shall favor the formation of ξ-PtAl2 phase; transformation of ξ-PtAl2 into β-(Ni,Pt)Al phase can be obtained via a heat treatment process; Cr, Co elements in the studied Ni-base superalloy substrates did not show significant influence on coating outer layer microstructure; while substrate elements affect the microstructure of the coating interdiffusion layer.