Wear Properties Of Plasma-based Low Energy Nitrogen Ion Implanted AISI316 Austenitic Stainless Steel

Plasma-based low energy nitrogen ion implantation has been used to modify AISI316 austenitic stainless steel with nitriding temperature of 400℃, base pressure of 1.5×10-3 Pa, nitriding pressure of 5×10-2 Pa and nitriding process time of 4 h. Component and structure of nitrided layer were characterized by using Rutherford backscattering spectroscopy (RBS), transverse cross-section metallography and x-ray diffraction (XRD). The nitrided layer consisted single high nitrogen face centred cubicγN phase with a nitrogen peak concentration of 35 at.% and a thickness of 13μm was obtained by plasma-based low energy nitrogen ion implantation, the microhardness of theγN phase layer was measured to be 22 GPa HVo.1 N·Tribological properties of nitrided and original AISI316 austenitic stainless steel have been investigated on a ball-on-disk tribometer against the same stainless steel counterface with a normal load of 2 N, a sliding speed of 0.16-0.39 m/s and a sliding time of 60 min under unlubricated condition. Wear behavior and mechanism of nitrided and original samples were investigated by using profilometer and scanning electron microscopy (SEM). Tribological experimental results have shown that for original samples, with the sliding speed increasing, the friction coefficient increased from 0.65 to 0.90, the depth of worn tracks increased from 3μm to 11μm, the width of worn tracks increased from 1435μm to 2061μm, the degree of plastic deformation for worn tracks increased, increasing sliding speed brought about a large amount of friction heat, which would aggravate the adhesion between the rubbing surfaces, leading to the severe adhesive wear of original samples. For nitrided samples, with the sliding speed increasing, the friction coefficient decreased from 0.85 to 0.70, the cross-sectional profilometer patterns of worn tracks appeared to be faint for all nitrided samples during sliding, and the width of worn tracks decreased which was observed from surface topography, there is no obvious change on the surface topography of worn tracks with the sliding speed increasing, an oxidative wear mechanism of nitrided samples was found instead of adhesive wear mechanism of original samples because theγN phase nitrided layer was prone to tribochemical oxidation on the worn surface due to the nitrogen supersaturation in austenitic matrix. The wear resistance of nitrided AISI316 austenitic stainless steel has been improved significantly by plasma-based low energy nitrogen ion implantation.