Surface Modification of W9Cr₄V₂Mo High Temperature Bearing Steel by Rare Earth Ion Implantation

Wear and corrosion are the main failure mechanisms of bearing steels and thus their properties must be improved to prolong their lifetime. Incorporation of rare earth elements have been investigated in processes such as plating, chemical heat treatment, and thermal spray. Ion implantation is an effective technique in the industry but there have been few reports about the use of rare earth ion implantation to improve the wear and corrosion resistance of hearing steels. In this work, 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 test, microhardness determination, and potentiodynamic polarization 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), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results show that the tribological properties and aqueous corrosion resistance of the treated samples were enhanced significantly. The improvement can be attributed to the oxide barriers and increasing cohesive strength of the oxide films. The mechanisms of the wear and corrosion behavior of the implanted specimens are also discussed.