Characterisation of detonation gun sprayed Cr 3 C 2 –25NiCr coatings on Ni and Fe based superalloys

Abstract

Cr₃C₂–25NiCr coatings are essential to provide protection against both wear and corrosion of superalloys particularly in the temperature range up to 900–1000°C. The Cr₃C₂–25NiCr coatings were deposited on the Fe and Ni based superalloys by D gun spray technique and subsequently investigated for their microstructural characteristics such as coating thickness, porosity, phase formation, microhardness, surface and cross-sectional morphologies. The coatings showed a dense microstructure with porosity contents less than 0·69%. The carbide grains of different size are uniformly cladded with the metallic binder and located around the splat boundaries as observed in the coatings. Lower carbide dissolution and its uniform distribution ensured a better binder protection in the coatings. High cohesive strength of the individual splats and high volume fraction of carbides contributed for the higher microhardness values of the coatings (775–1200 HV).