Microstructural studies of effect of Ni and Ni-20-Cr particles plasma sprayed on to stainless steel substrates

Plasma spray processing is a coating spray technology in the family of thermal spray processes, in which powder particles are simultaneously heated and accelerated in a gas kept in a plasma state using an electric arc. In this study, pure Ni and Ni-20-Cr powders were plasma sprayed onto polished stainless steel substrates at room temperature. Detailed microstructural investigation of the splat-substrate interface was carried out by using scanning electron microscopy (SEM), focused ion beam (FIB) microscopy and transmission electron microscopy (TEM). The additions of Cr promoted better adherence of the splat to the substrate and modified splat formation by reducing splashing. Chromium addition also increased the portion of disk-shaped splats. More intriguingly, energy dispersive spectroscopy (EDS) mapping, performed in the TEM, showed inter-diffusion and/or inter-mixing between the splat and the substrate, whereby ‘jet’ of iron-based material, presumably from the substrate were observed to be intimately intermixed into the interior of the nickel splat.