Effect of plasma nitrocarburising on fatigue resistance of low alloy Cr–Mo sintered steel

AbstractA nitrocarburising treatment was carried out on a low alloyed Cr–Mo sintered steel (1·5%Cr, 0·2%Mo) to evaluate its influence on the bending fatigue resistance of the material. Fatigue performance was compared with that obtained by a conventional through hardening and a plasma carburising. Two different green densitise (7·1 and 7·4 g cm−3) and two different sintering temperatures (1120 and 1250°C) were adopted during preparing the as sintered steels. Fatigue strength after nitrocarburising on 1120°C sintered steels considerably increases. It is comparable with that obtained by through hardening and slightly better than that obtained by plasma carburising. On samples sintered at 1250°C the fatigue resistance of the nitrocarburissed is worse than expected, because the microstructure is softer and less homogeneous.