Corrosion and wear resistance of 32CrMoV13 steel nitrided by plasma

Abstract

This paper presents corrosion and wear behavior of the plasma-nitrided 32CrMoV13 steel. Untreated and plasma nitrided samples were tested. The structure of layers was determined by X-ray diffraction, the morphology was observed by scanning electron microscopy (SEM). The corrosion behavior was evaluated by electrochemical techniques (potentiodynamic curves and electrochemical impedance spectroscopy). The corrosion tests were carried out in acid chloride solution (HCl 1 M). The plasma nitriding behaviors of 32CrMoV13 steel have been assessed by evaluating tribological properties and surface hardness by using a pin-on-disk wear machine and microhardness tester. Experimental results showed that the nitrides ε-Fe_2-3N and γ′-Fe₄N present in the white layer are nobler than the substrate but may promote, by galvanic effect, a localized corrosion through open porosity. Better corrosion protection was observed for the nitrided sample. It is found that plasma nitriding improves the wear rate, and the presence of a hard and brittle compound layer on the surface causes an increase in wear of the specimen surface.