Plasma nitriding of AISI 316L austenitic stainless steels at anodic potential

Plasma nitriding experiments were carried out with pulsed dc glow discharge plasma in ammonia atmosphere at temperatures ranging from 450 to 540 °C for 4 h. In this process, the AISI 316L austenitic stainless steel samples were set on a plate at anodic potential. The phase composition, the thickness and morphology of the nitrided layer, as well as its surface hardness, were investigated using X-ray diffraction, glancing angle X-ray diffraction, optical microscopy, scanning electron microscopy and microhardness tester. The results showed that the microstructure and phase composition depended on the nitriding temperatures. In particular, a nitrided layer consisting of 3-layered structure was formed on the sample nitrided at 510 and 540 °C. The surface microhardness values and the thickness of the hardened layers increased as the nitriding temperature increased. In addition, the corrosion and wear properties of the untreated and nitrided samples were evaluated. The results showed that anodic plasma nitriding of austenitic stainless steel was a suitable process for improving the surface hardness and wear resistance properties without deteriorating corrosion resistance.