Wear and corrosion properties of AISI 420 martensitic stainless steel treated by active screen plasma nitriding

Abstract

AISI 420 martensitic stainless steel was treated by active screen plasma nitriding. The test table was placed inside the steel screen but isolated from the cathodic potential. The specimens, together with the furnace wall and test table, were earthed, resulting in formation of anodic potential. Treatments were carried out in NH3 atmosphere of 400Pa for 6h at temperature ranging from 440 to 520°C. The specimens were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and micro-hardness measurement. The results showed that anodic nitriding treatments were able to produce different types of modified surface layers at different temperatures. The thickness of the nitrided layers and surface roughness increased with the nitriding temperature. Dry sliding wear tests and electrochemical corrosion tests were conducted on the untreated substrate and nitrided specimens. It can be concluded that active screen plasma nitriding at anodic potential improved the hardness, wear resistance, and corrosion properties of AISI 420 stainless steel.