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.
Surface layer hardness and concentration profiles of austenitic stainless steels after
plasma carburizing and /or nitriding at 673 K were investigated. Carbon and nitrogen concentration
were measured by glow discharge optical emission spectrometry (GDOES) and carbides or nitrides
were detected by x-ray diffraction analysis (XRD) and TEM. The state of carbon at the treated
surface was investigated by Raman spectroscopy. Separation of carburized layer and nitrided layer
was observed in a simultaneous carburizing and nitriding plasma treatment.
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