Abstract: Effects of AC pulse voltage, DC pulse bias voltage and temperature on surface hardness and nitrided layer thickness of 316 stainless steel were studied by orthogonal test, and the optimal process parameters of double power supplies for low temperature nitriding were obtained. The properties of the nitrided specimens treated by optimal process were evaluated by means of optical microscope (OM), X-ray diffraction (XRD), microhardness tester, electrochemical workstation and friction and wear tester. The results show that the order of factors affecting properties of the nitrided specimens is: AC pulse voltage＞temperature＞DC pulse bias voltage. The optimum process parameters are AC pulse voltage of 360 V, DC pulse bias voltage of 270 V, and temperature of 380 ℃. Compared with single power supply, the thickness of nitrided layer treated by double power supplies is 43.4 μm, which is 8.5 times of single power supply; the surface hardness is 1350 HV0.025, which is 3.1 times of single power supply; the self-corrosion potential increases from -256 mV(vs SCE) to -180 mV(vs SCE), and the self-corrosion current density decreases from 13.90 μA/cm² to 0.45 μA/cm²; the friction coefficient is reduced from 0.55 to 0.42. The increase of nitriding rate of double power supplies is due to the surface structure defects caused by high energy ion bombardment and the high dissociation of nitriding gas.

Key words: 316 stainless steel, low temperature ion nitriding, double power supplies, high nitriding rate, wear resistance, corrosion resistance