Improvement of nitrogen ion implantation on the wear and corrosion resistance of bearing steel in NaCl solution

Abstract

Nitrogen ion implantation has been used to improve the wear and corrosion resistance of bearing steel. A comprehensive investigation was carried out to study the changes in chemical state, microstructure, nanohardness, and surface free energy after ion implantation. The wear and corrosion properties were investigated in the study. The results showed that a metal nitriding layer and an amorphous layer were formed on the surface of the N-implanted sample. The nanohardness of the N-implanted sample increased by 70.28 %, and the surface free energy decreased by 28.39 %, indicating an increase in hydrophobicity, compared to the untreated sample. In the tribological test, the coefficient of friction increased slightly, but the volume loss rate decreased by 55.2 % after ion implantation. The wear mechanism changed from adhesion and abrasive wear of the untreated samples to abrasive wear of the N-implanted samples. Electrochemical corrosion tests showed that the polarization resistance increased and the corrosion current density (icorr) decreased from 6.506 × 10−6 A/cm2 to 1.718 × 10−6 A/cm2 after ion implantation. The improvement in corrosion resistance was attributed to the increase in surface hydrophobicity and the formation of an amorphous layer. The amorphous layer effectively reduced surface defects, protected the substrate, inhibited local pitting, and improved corrosion resistance.