Influence of Nitrocarburizing and Post-Oxidation on Surface Characteristics, Fatigue, and Corrosion Fatigue Behaviour of AISI 4330V Steel

In the present work, gaseous nitrocarburizing followed by water spray oxidation in vacuum was carried out on 4330V steel. The X-ray diffraction analysis showed that the thermochemically modified surface layer mainly consisted of e-Fe2-3(N,C), γ′-Fe4(N,C), and magnetite (Fe3O4). To quantify the residual stress generated due to surface treatment, the Sin2ψ method was used. Residual stress of compressive nature up to a depth of 1 mm was observed, and its maximum value was 383 MPa. Nitrocarburizing followed by oxidation not only increased the surface hardness but also decreased the wear loss. The synergistic effect of corrosion-resistant phases formed after surface treatment improved surface hardness and compressive residual stress which resulted in the enhancement of corrosion fatigue life.