Plasma-based low-energy ion implantation of austenitic stainless steel for improvement in wear and corrosion resistance

Plasma-based low-energy ion implantation, including plasma source ion nitriding/carburizing and plasma source low-energy ion-enhanced deposition, has emerged as a low-temperature surface engineering technique for steel and alloys. In this work, the effects of nitrogen alloying on the wear and corrosion resistance of the plasma source ion nitrided 1Cr18Ni9Ti austenitic stainless steel have been investigated in order to produce a combined improvement in wear and corrosion resistance. A high-nitrogen face-centered-cubic (f.c.c.) phase (γN) with the different nitrogen contents formed on the nitrided stainless steel was characterized using Auger electron spectroscopy, electron probe microanalysis, glancing-angle X-ray diffraction and transmission electron microscopy. The wear tests were performed on a pin-on-disc tribometer in which the γN-phase samples were rubbed against a hardened Cr12MoV high-alloy steel disc (HRC 62–63) under a normal load from 2.2 to 39 N using Cr2O3 powders in machine oil as the abrasive media. The corrosion resistance was analyzed in 1% NaCl and 0.5 mol l−1 H2SO4 solutions by the electrochemical polarization technology. The γN-phase samples have a high microhardness of about HK0.1N 22 GPa and a high load-bearing capability, leading to significant improvement in wear resistance, especially under the high normal loads. The high nitrogen content in the γN phase resulted in higher wear resistance through the formation of a thicker hardened layer. The γN-phase samples have a high pitting corrosion resistance and a similar general corrosion resistance compared with those of the original stainless steel. The nitrogen content in the γN phase mainly affected the pitting corrosion resistance and slightly affected the general corrosion resistance.