Formation of Graphite Phase in Powder Metallurgical Ultrahigh Carbon Steels with High Wear Resistance

Carbon with different forms and morphologies plays a key role in the wear resistance of ultrahigh carbon steels (UHCS). In this study, UHCS with carbon contents from 1.4 to 1.9 wt% are prepared through powder metallurgy route, and an organic compound is used as the carbon source. The microstructures, mechanical properties, and wear resistance of UHCS are investigated. Results show that the graphite phase is formed in UHCS, and the morphology of graphite changes from granular to irregular strip‐type with the increase of carbon content. The synthesized UHCS show improved wear resistance compare to other reported UHCS with no graphite. Moreover, the UHCS with 1.7 wt% C is found to have the best wear resistance with a wear rate of 4.14 × 10⁻⁶ mm³/N · m. Besides, it is found that the wear rate and the coefficient of friction (COF) of UHCS increase after heat treatments. This is mainly due to the diffusion of carbon into the matrix, which leads to the reduction of graphite. The results are much helpful for preparing UHCS with controllable graphite morphology, and better wear resistance.