Low Temperature Plasma Nitriding of Low Alloy Steel for the Enhancement of Hardness

Abstract

The present concerns surface modification of low alloy CrMoV steel by following the route of plasma nitriding for the improvement of hardness. Plasma nitriding was performed at a low temperature of 450 oC. The maximum hardness at this lower temperature was found to be ∼1270 Hv after nitriding. At 550 oC though the hardness improvement near the surface region was similar but the core hardness was reduced. XRD studies revealed various nitrides of iron (γ′ (Fe4N) and ε (Fe2–3N)) with the ε nitride as the dominant phase. SEM analyses revealed the surface microstructure with almost no white layer. EDS point analyses shown the signature of N on the surface layer. It has been concluded in this study that the hardness of 90CrMoV8 steel can be improved significantly even at a low temperature of 450 oC without any of risk of the loss of core hardness.