Surface gradient CoCrMo alloy generated by carbon ion implantation with enhanced tribocorrosion resistance

The CoCrMo alloy was ion implanted by carbon with implantation fluences from 1.0 × 10¹⁷ to 9.0 × 10¹⁷ ions/cm². The nanostructure and phase transformation in CoCrMo alloy due to carbon ion implantation were investigated using high-resolution transmission electron microscopy (HRTEM). The tribocorrosion behavior was investigated by using a ball-on-disk reciprocating wear tester equipped with a three-electrode electrochemical cell. It is found that the carbon ion-implanted CoCrMo alloy is composed of an amorphous layer, a transition layer with mixed amorphous/nanocrystalline, and the base material. The stacking faults (SFs) and nano ε-martensite enriched region are formed underneath the transition layer at higher implantation fluence. The material loss due to tribocorrosion is decreased by one order of magnitude after carbon ion implantation. The enhanced tribocorrosion performance can be explained by the formation of amorphous layer and the nanocrystallization during carbon ion implantation.