Surface modification of W9Cr4V2Mo high-temperature bearing steel by rare earth ion implantation

Wear and corrosion are the main failure mechanisms of bearings and it is important to prolong their working lifetimes by improving the bearing surface properties. Incorporation of rare-earth elements is one of the viable means in many technologies such as plating, chemical heat treatment, and thermal spraying. In this work, various kinds of rare earth ions including praseodymium, lanthanum and neodymium were implanted into W9Cr4V2Mo high-temperature bearing steel specimens using a metal vapor vacuum arc source. Pin-on-disk wear tests and microhardness and potentiodynamic polarization measurements were employed to evaluate the mechanical properties and chemical stability of the treated specimens. The chemical composition and surface morphology of the implanted layers were characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Our results indicate that the tribological characteristics of the treated samples are affected significantly due to the smoother and harder surface, while the enhancement of the corrosion resistance in the 3.5 wt.% NaCl aqueous solution after ion implantation is not appreciable. The modified surface yields better wear resistance.