Plasma and vacuum carburizing processes and mechanical properties of SCM 415 steel

The plasma and vacuum carburizing processes are innovative surface modifica tion techniques for potential applications in manufacturing processes of ve hicle components. In this study, the influence of this relatively new proce ss on the surface hardness of SCM 415 low-alloy steel (0.15% C) was investi gated under various process conditions involving gas composition, gas press ure, plasma current density, temperature and time. The effective plasma car burizing temperature of SCM 415 steel was found to be higher than 850 degre es C, and the case depth was proportional to the square root of carburizing time under the same current density. Also, high cycle fatigue and dry wear characteristics of vacuum carburized SCM 415 steel were evaluated after va rious heat treatments. Comparing the fatigue and wear characteristics of va cuum carburized specimens to those of hot annealed or reheat quenched speci mens, the wear resistant property as well as bending fatigue limits were fo und to be substantially improved. The optimum amount of retained austenite exists for the maximum fatigue strength in vacuum carburized steels. Throug h quantitative analysis of the retained austenite using X-ray diffractomete r, this value was found to be about 4%.