Three-body abrasion of surface engineered die steel at elevated temperatures

Abstract

Surface engineering techniques are being considered in the hot forging industry, for improving the life of forging dies. During forging, the surfaces of the dies reach temperatures of 700–800 °C. Published information on the wear performance of modified/engineered surfaces at higher temperatures is, however, scarce. To address this situation, a high-temperature pin-on-disc machine was modified into a ring-on-disc arrangement to facilitate the introduction of abrasive particles into the system, so that three-body abrasion tests could be conducted. In this paper, the results obtained from this machine on various modified surfaces at temperatures up to 600 °C in air using alumina abrasive particles are presented and discussed. The surface treatments studied include hardfacing with Satellite 6, pack boriding, gas nitriding and nitrocarburising. For some treatments, the test results indicated a decrease in wear rate with increasing temperature, but for others there was no change with temperature. The wear track on the siscs were examined by light microscopy and scanning electron microscopy (with energy dispersive X-ray spectroscopy) to determine the wear mechanisms of the modified surfaces. Microcutting is believed to be one of the mechanisms occurring in these tests. The hot strength of the surface layer, however, determines the performance at higher temperatures. The importance of surface oxidation and of abrasive embedment in the surface, in determining the abrasive wear rates, is also discussed.