Sand slurry erosive wear of thermal sprayed coating of stellite

Abstract

The present paper describes the sand slurry erosive wear behaviour of the flame sprayed stellite (Co–Cr–W–Ni–C) coating. The wear behaviour was evaluated with the help of a slurry pot tester by using two sand slurry concentrations (20 and 40% sand particles) at different rotational speeds (600–1000 rev min−1). It was observed that the weight loss of the coating material and rotational speed relationship is governed by the concentration of sand particles in slurry. Slurry erosive wear of the coating showed that in case of 20% silica sand slurry, weight loss increases with increase in rotational speed from 600 to 1000 rev min−1 while in case of 40% silica sand slurry weight loss first increases with increase in rotational speed from 600 to 800 rev min−1 followed by marginal decrease in weight loss with further increase in rotational speed from 800 to 1000 rev min−1. Improvement in wear resistance of mild steel due to development of the thermal sprayed coating was calculated as wear ratio which is a ratio of weight loss of mild steel and that of coating. Wear ratio was found in range of 4·2–7·5 under different test conditions. The microstructure study showed polyhedral shaped Cr dominated carbide particles in eutectic matrix. The average microhardness of the coating was 680 HV. Wear behaviour of coating has been discussed in light of microstructure and microhardness of coating. Scanning electron microscopy study of wear surface showed that loss of material from the coating takes place by indentation, crater formation and lip formation and its fracture.