Acceleration of Carbon Diffusion by Molybdenum in Low-Temperature Plasma Carburizing of Austenitic Stainless Steel

Abstract

Surface hardening of austenitic stainless steel without degradation of corrosion resistance has been a subject of continuing interest in the field of surface of engineering technology. In this paper, we elucidate a hardening mechanism, changing the amount of the molybdenum (Mo). Three austenitic stainless steel were used in the present work, AISI304 (0.21%‐Mo), AISI316 (2.34%‐Mo), and AISI317L (3.13%‐Mo). Samples were plasma carburized using a DC plasma apparatus under 667 Pa of mixed gas flow of 5%CH4 + 45%H2 + 50%Ar at 673 K or 723 K for various durations. The surface hardness increased by increasing the amount of the Mo. The lattice constant after carburizing also increased with increasing Mo contents. These results indicate that carbon super saturation was enhanced by the effect of large Mo atoms, which can widen the octahedral sites.