The effect of sand blasting pretreatment on plasma nitriding

In this study, sand blasting was conducted as a pretreatment prior to plasma nitriding, and the effect of sand blasting on plasma nitriding was evaluated by means of scanning electron microscopy (SEM), optical microscopy, X-ray diffraction (XRD), electrochemical polarization and pin-on-disk tribotester etc. The results showed that sand blasting could enhance the nitriding efficiency and bring about much thicker nitrided layer than that of the nitrided-only sample under the same plasma nitriding condition, and the higher nitriding efficiency could be ascribed to the higher surface free energy (SFE). Electrochemical measurements showed that the sand-blasted sample increased the corrosion potential by approximately 100 mV and a reduced the corrosion current by an order of magnitude in comparison with the nitrided-only sample. Meanwhile, the cross-sectional hardness and wear resistance were significantly improved, which could be attributed to the thicker compound layer with higher amount of ε-Fe2-3N comparing with the nitrided-only sample.