AISI 316 L austenitic stainless steels (316 L SS) were nitrided to enhance their mechanical property and corrosion resistance by a high efficiency low-pressure arc plasma nitriding process at low temperature (~ 400 °C). Arc currents ranging from 55 A to 95 A were applied to generate the arc plasma. The effect of arc current on the microstructure, mechanical property of the nitrided layers was investigated by using XRD, SEM, TEM, Vickers microhardness tester and ball-on-disk tribometer, respectively. The corrosion resistance was also evaluated by potentiodynamic polarization in 3.5% NaCl solution. The results showed that the nitrided layers consisted primarily of the expanded austenite (γN) phase with a trace of a mixture of CrN and Fe3N. The thickness of nitrided layer could reach 15 μm in 1 h at 400 °C in virtue of the high-density and high-energy nitrogen plasma generated from this process, which showed an extremely fast nitriding kinetics. Due to the solution strengthening of the nitrogen super-saturation γN-phase formed on the surfaces of the samples, the surface microhardness and the wear resistance of the nitrided 316 L SS was significantly improved.
The worn surfaces revealed that worn behavior of the low current (below 85 A) nitrided samples was remarkably dominated by micro-abrasion and spalling holes, while the 95 A sample was worn in a mode featured by cracks and spalling blocks. Besides, because chromium nitride precipitation was eliminated, the nitrided samples still showed excellent corrosion resistance, which was comparable to untreated 316 L SS