Influence of microstructure on the wear and corrosion behavior of detonation sprayed Cr2O3-Al2O3 and plasma sprayed Cr2O3 coatings

Abstract

Cr2O3-20wt% Al2O3 cermet composite and Cr2O3 coatings were deposited by the detonation spray coating (DSC) and air plasma spray techniques on Ti-6Al-4V substrates. The microstructure and phase formation in the coatings were analysed. Micro hardness and fracture toughness of coatings were measured using Vickers diamond pyramid indenter. Owing to the well-defined layered structure with individually richer Cr2O3 and Al2O3 phases together with oxide-based solid solution at the splat boundaries, the DSC Cr2O3-Al2O3 composite coating exhibits dense microstructure and better indentation fracture toughness than the well established plasma sprayed Cr2O3 coating. Although the plasma sprayed Cr2O3 coating also exhibits layered structure; the relatively poor indentation fracture toughness is attributed to the significantly higher porosity and weaker inter-splat bonding. Towards understanding the relative tribological behavior, the sliding and three-body abrasive wear tests were conducted. The material removal mechanism and associated degradation behavior of detonation sprayed Cr2O3-Al2O3 coating has been correlated with coating microstructure comparatively against the plasma sprayed Cr2O3 coating. Electro-chemical corrosion tests of coatings in salt solution (artificial sea water) reveals an improved corrosion protection by Cr2O3-Al2O3 composite coating as compared to Cr2O3 coating. Enhanced tribological performance and corrosion resistance was attributed to the dense and crack free structure of Cr2O3-Al2O3 composite coating than its counterpart.