Influence of nitriding on corrosion resistance of martensitic X17CrNi16-2 stainless steel

Nitriding increases surface hardness and improves wear resistance of stainless steel. However, nitriding can sometimes reduce their corrosion resistance. In this paper, the influence of nitriding on the corrosion resistance of martensitic stainless steel was investigated. Plasma nitriding at 440 oC and 525 oC and salt bath nitrocarburizing were carried out on X17CrNi16-2 stainless steel. Microhardnes profiles of the obtained nitrided layers were examined. Phase composition analysis and quantitative depth profile analysis of the nitrided layers were performed by X-ray diffraction (XRD) and glow-discharge optical emission spectroscopy (GD-OES), respectively. Corrosion behaviour was evaluated by immersion test in 1% HCl, salt spray test in 5% NaCl and electrochemical corrosion tests in 3.5% NaCl aqueous solution. Results show that salt bath nitrocarburizing, as well as plasma nitriding at low temperature, increased microhardness without significantly reducing corrosion resistance. Plasma nitriding at a higher temperature increased the corrosion tendency of the X17CrNo16-2 steel.