Influence of welding technique and temperature on fatigue properties of steel deposited with Co-based alloy hardfacing coating

This paper aimed to investigate the influence of welding technique and temperature on fatigue properties of heat-resistant steel with hardfacing coatings. The plasma transferred arc welding (PTAW) and the oxy-acetylene welding (OAW) were employed. The rotating bending fatigue tests were performed at room temperature (RT) and 500 °C. It was found the fatigue strength with 107 cycles of OAW specimens at RT was lower than that of PTAW ones, possibly resulting from the higher amount of carbides in OAW coatings. The fatigue strength with 107 cycles at 500 °C was higher than that at RT, which was mainly due to the interface delamination and the increase in ductility with increasing temperature. Two failure modes, i.e. the coating failure mode at RT and the coating-interface failure mode at 500 °C, were proposed. The fatigue life was predicted with the model considering the characteristic geometry of inclusions, the average hardness of coating, and the effect of external stress.