Microstructural evolution of silicon-platinum modified aluminide coatings on superalloy GTD-111

The microstructure evolution of (Si,Pt)-modified aluminide coatings has been investigated. Coatings were prepared by slurry silico-aluminizing of different thicknesses of platinum-electroplated GTD-111 Ni-based superalloy. Microstructure and phase characterizations were conducted by means of SEM, EDX, XRD and EPMA. The composition of the coating's outer layer altered from single β-(Ni,Pt)Al phase to two phase β-NiAl + PtAl2 by increasing the initial Pt thickness. Silicon diffusion into the coating is shown to be less in the presence of the PtAl2 phase. Furthermore, refractory metal-containing precipitates in the outer two phase layer of the platinum modified coating were replaced by silicides in the corresponding (Si,Pt)-modified aluminide coating.