FIB assisted study of plasma sprayed splat–substrate interfaces: NiAl–stainless steel and alumina–NiAl combinations

This paper deals with the splat–substrate and intersplat interfaces of splats produced from Ni–5 wt.% Al and alumina based ceramic powders. The cross section of the splat–substrate interface was studied using a focused ion beam (FIB) assisted Field Emission Scanning Electron Microscope (FE-SEM). The metallic splat showed good interfacial integrity apart from a few interfacial pores resulting from entrapped gases and edge curl resulting from quenching stresses. The ceramics showed generally well adherent interfaces for both single and multilayer splats. Good adherence of both alumina splats was attributed to the improved wettability provided by the bond coat. One kind of alumina splats, namely, those obtained from agglomerated nanostructured powder was found to be free from crack and edge curl. This was attributed to the presence of a glassy phase in this splat, which can absorb quenching stresses.