On microstructure, hardness and wear behaviour of flame sprayed Co base alloy coating deposited on mild steel

Abstract

In the present paper, the influence of preheat and post-spray heat treatment temperature on microstructure and adhesive wear behaviour of flame sprayed Co base hard facing alloy (EWAC 1006 EE) coatings on mild steel has been reported. Coatings were deposited by oxyacetylene thermal spraying torch. Thermal spraying of substrate was carried out at two preheat temperatures, i.e. 300 and 350°C. The post-spray heat treatment of the coatings was carried out at three different temperatures: 650, 750 and 850°C, for 2 h. Wear resistance of coatings was evaluated using ring on block wear system at 40 N normal load and 1 m s-1 sliding speed of ring. Hardness of coating, base metal and interface was tested using Vickers hardness testing machine. Optical studies of the microstructure of the substrate, interface and coating were carried out to investigate the influence of preheat and post-spray heat treatment temperatures. It has been found that an increase in post-spray heat treatment temperature enhances the hardness and wear resistance of the coating. © 2006 Institute of Miterials, Minerals and Mining.