Effect of interlayers on the microstructure and wear resistance of Stellite 6 coatings deposited on AISI 420 stainless steel by GTAW technique

Abstract

In this paper, a comparative study has been conducted on Stellite 6 weld overlays deposited on the surface of AISI 420 martensitic stainless steel turbine blade with and without use of AISI 309L austenitic stainless steel and Stellite 6 interlayers using gas tungsten arc welding (GTAW) technique. The coatings were then investigated to reveal their microstructure, phase characterization, and hardness using optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction technique (XRD), and Vickers microhardness (HV0.3). In addition, wear tests were carried out using pin-on-disk testing apparatus at room temperature in order to study the wear resistance of coatings. Worn surfaces and debris obtained from the wear tests were investigated by SEM, and EDS. The results showed that the microstructure of Stellite 6 weld overlays includes carbide phases dispersed in the interdendritic regions of the matrix with a dendritic structure. Furthermore, the amount of Fe decreased in the coatings and the chance of creating effective carbides increased with an increase in the number of Stellite layers and implementation of the interlayer. Hence, it was observed that applying the interlayers made considerable effects on dilution resulting increase in the hardness and wear resistance of weld overlays.