Active Screen Plasma Nitriding Characteristics of 347H Austenitic Stainless Steel

Abstract

Effect of active screen plasma nitriding (ASPN) on microstructure, hardness, and wear loss of 347H austenitic stainless steel (AuSS) was studied at various processing parameters. Scanning electron microscopy, x-ray diffraction (XRD), hardness, and wear tests were performed on samples. The XRD analysis showed the presence of S-phase (γ_N-expanded austenite) in samples nitrided at 350 °C and 400 °C. In contrast, samples nitrided at higher temperatures ranging from 450 to 550 °C showed the presence of various types of nitride phases in the nitrogen-enriched layer. The case depth and mass of nitrided samples increased with the increase in nitriding temperatures owing to the increase in diffusivity of nitrogen at a higher temperature. The wear loss of samples nitrided at higher temperatures was lower than those nitrided at lower temperatures due to the formation of a higher amount of hard nitride phase(s) in the nitrogen-enriched layer at temperature ≥ 450 °C.