Room and high temperature wear behaviors of nickel and cobalt base weld overlay coatings on hot forging dies

Abstract

The lifetime of dies used for production of forged parts is variable and determined by wear rate, plastic deformation, thermal and mechanical fatigue. These tools are subjected to extreme temperature at high unit pressures for short durations and must withstand multiple cycles while maintaining dimensional stability. This paper is an investigation into the use of nickel and cobalt base superalloys as wear resistant hardfacing materials on H11 tool steel. Three weld overlay alloys including Inconel 625, Stellite 6 and Stellite 21 were deposited on H11 steel substrates using tungsten inert gas welding (TIG) process. Wear tests were carried out using a pin-on-disk wear tester at room temperature and 550 °C. Microhardness of the weld overlays was obtained and the worn surfaces were examined by scanning electron microscopy (SEM). The results of the laboratory tests were then compared with the results obtained from field studies. The results showed a much lower wear at high temperature with the weld overlays due to formation of smooth compacted oxide layers on the wear surfaces. Inconel 625 showed the best wear behavior among the weld overlays at high temperature.