Experimental investigation on post-processed NiCr thermal barrier coating and its sliding wear behaviour

Abstract

NiCr metal is deposited on martensitic stainless steel using an atmospheric plasma spray method. To enrich the metallurgical properties of the NiCr metallic coating, a standard heat treatment process is adopted. From the investigation, it has been shown that the voids and porosity developed during the thermal spray have been controlled through heat treatment. Electron image analysis reveals that the coating has reduced porosity with strong and dense bonding strength. With reference to the surface hardness, the post-processed coating yields a maximum of 140 Hv compared with the coated (129 Hv) and base metal (115 Hv). Subsequently, the sliding wear behaviour of post-processed NiCr coating has a minimum wear of 25 μm for an applied load of 5 N and 57 μm for an applied load of 15 N. Owing to the high metallurgical bonding, the coating has sustained the heavy loads, and the wear formation is controlled. However, the base metal has an adhesive wear mechanism caused by the high frictional force on the sliding friction. Therefore, it is recommended that post-processed thermal barrier coatings possess good metallurgical bonding and withstand heavy load causing minimum wear.