Investigations on inter-splat boundaries of cold sprayed Ni[sbnd]Cr coatings upon high temperature oxidation

Abstract

Deposition of NiCr through cold spraying has potential implications in power sector as a potential candidate for high temperature oxidation and corrosion resistance coating. In this work, cold spray deposition of NiCr at different stagnation temperatures varying from 600 °C to 800 °C using air as process gas instead of expensive nitrogen and helium gases is realised. The bonding state at the inter-splat boundaries was simulated and the same was correlated with the results obtained from mechanical and thermal cycling studies. Coatings deposited at higher temperature exhibit superior performance due to the formation of strong inter-splat boundaries, thus reflected in porosity and oxidation resistance. Deposition conditions (VP / VCr) used in this study meets the requirement for inter-splat bonding. The fraction of bonded inter-splat boundaries achieved at 20 bar 800 °C was estimated to be ~100 % thus reflects in functional properties such as porosity, microstructure, superior oxidation and spallation resistances.