EFFECT OF NITROGEN HYDROGEN RATIO ON PLASMA NITRIDING FOR 38CrMoAl

Critical nitrogen hydrogen ratio in plasma nitriding was primarily investigated to get enhanced performance for 38CrMoAl steel. The modified surface layer was characterized by optical microscopy (OM), X-ray diffraction (XRD) and micro-hardness tester. The results showed that the critical nitrogen hydrogen ratio was 1: 5 while plasma nitriding at 540 degrees C for 6 h. Under this condition, no compound layer was formed, and accompanied with high surface hardness, while the compound layer was formed accompanied with lower surface hardness with nitrogen hydrogen ratio higher than the critical value.