Plasma immersion ion implantation of 100Cr6 ball bearing steel

Most low alloy steels are tempered al relatively low temperatures, limiting the opportunities for improving their wear resistance and surface hardness by traditional heat treatment processes. In this work, we use plasma immersion ion implantation (PI3) to apply a hybrid ion implantation/thermochemical diffusion treatment to ball bearing steel 100Cr6 (1% C, 1.5% Cr). By a judicious choice of implantation voltage, temperature and time, it is possible to combine the PI3 treatment with the tempering stage of heat treatment, without compromising the hardness of the alloy. Up to 200 degrees C, the bulk hardness (750 HV tempered) of the material is maintained, and nitrogen implantation increases the surface hardness due to the precipitation of fine Fe2N. At 300 degrees C, where enhanced nitrogen and carbon diffusion can occur, the bulk hardness decreases, although in many applications this can be compensated by the increase in surface hardness to around 900 HV0.1 due to Fe3N and Fe4N formation. Wear and corrosion tests reveal significant improvements in comparison with untreated steel.