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

Abstract

The NiCr metal is deposited on martensitic stainless steel using 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 clarified that the voids and porosity developed during the thermal spray has been controlled through the heat treatment. Electron image analysis reflects that the coating has reduced porosity with strong and dense bonding strength. With reference to the surface hardness, the post processed coating yields maximum of 140 Hv compared to as coated (129 Hv) and base metal (115 Hv). Subsequently the sliding wear behaviour of post processed NiCr Coating has a minimum wear 25µm for 5N and 57µm for 15N applied load respectively. Due to the high metallurgical bonding, the coating has sustained the heavy loads and the wear formation is controlled. However, the base metal has adhesive wear mechanism due to high frictional force on sliding friction. Since, it is recommended that the post processed thermal barrier coatings can possess good metallurgical bonding and withstand heavy load causing minimum wear.