On Process Study Of Plasma Source Nitrided AISI316Austenitic Stainless Steel

Plasma source nitriding is a novel nitriding technology which can overcome the common problems associated with conventional dc plasma nitriding, such as difficulties in maintaining a uniform chamber temperature, arcing and hollow cathode effects. In this paper, the effect of process parameters, including nitriding temperature, nitriding pressure, sample position and sample potential, on metallographic, phase structure, composition, microhardness, surface roughness and corrosion resistance of the nitrided layer on plasma source nitrided AISI316austenitic stainless steel was studied systematically, and a technical characteristic map was given, in order to supply a theoretical basis for practical application.For floating potential, nitriding pressure of300Pa, a distance of100mm between screen and sample, with the nitriding temperature of350-500℃, thickness, nitrogen concentration, microhardness and surface roughness (Ra) of the nitrided layer was2-14μm,18-21at.%, HV0.1n10.5-15.5GPa and0.022-0.120μm, respectively. The nitrided layer possessed good comprehensive properties with a nitriding temperature of400-450℃. The precipitation of CrN phase at500℃led to the deterioration of the pitting corrosion resistance.For floating potential, nitriding temperature of450℃, a distance of100mm between screen and sample, increasing the nitriding pressure from300Pa to500Pa, thickness and nitrogen concentration of the nitrided layer decreased from14μm,21at.%to7.5μm,18at.%, respectively, and microhardness and surface roughness also decreased.The composition and properties of the nitrided layer depended on the position and potential of sample. For floating potential, nitriding temperature of450℃, nitriding pressure of300Pa, a distance of20-100mm between screen and sample, thickness and nitrogen concentration of the nitrided layer was14-15μm and20-25at.%, respectively. Increasing the distance to150mm and200mm, thickness and nitrogen concentration of the nitrided layer decreased to9μm,15at.%and7μm,17at.%, respectively. And the nitrided layer had lower microhardness and surface roughness. Compared with floating potential, thickness and nitrogen concentration of the nitrided layer increased1-4μm and1-3at.%, respectively, and microhardness and surface roughness of the nitride layer also increased obviously with a voltage of200V bias.