高濃度浸炭用鋼のプラズマ浸炭および疲労特性

概要

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Super carburizing is one of the carburizing processes where surface carbon content is increased up to 2 to 4%, extremely higher than that of conventional one. This is characterized by its carbide precipitation in the case and is expected to show superior fatigue durabilities.At first the effect of plasma super carburizing conditions on the carbide morphology was studied using 0.18%C-0.5%Si-2.25%Cr-0.4%Mo steel. Low temperature carburizing at 1143K was confirmed to be effective to obtain finely and uniformly dispersed carbides. Furthermore, the optimum condition was selected with taking other case properties into account.The bending and contact fatigue tests were carried out as a next step, and it was revealed that plasma super carburized steel exhibited superior fatigue durabilities to those of conventionaly carburized JIS-SCM 420. The superiority was considered due to its higer surface hardness, finer grain, intergranular oxidation free case and higher elevated temperature hardness.