Effect of Rare Earth Metal Yttrium on Microstructure and Wear Resistance of Vacuum Fusion Sintered Ni-Based Coating

The effect of rare earth metal yttrium on the microstructure, chemical composition, hardness, and wear resistance of vacuum fusion sintered Ni-based coatings was studied. Thus the elemental compositions and phase compositions of the alloy coatings were determined using an energy dospersive X-ray analyzer and an X-ray diffractometer, respectively. The friction and wear behaviors of the coatings were evaluated on an MM-200 test rig in a lock-on-ring configuration under oil-lubricated condition. The worn surface morphologies of the coatings were observed using a scanning electron microscope. The results showed that the rare earth metal yttrium was beneficial to improving the microstructure of Ni60 coating, restraining the precipitation of the needle-shaped phase, and making the size of the sphere-shaped decreased. Moreover, yttrium helped to alleviate the dilution function of the Fe atom from the steel matrix to the Ni-based alloy coating, while it was able to decrease the Fe content and increase the Ni and Cr contents of the coating. Besides, yttrium contributed to greatly increasing the hardness and wear resistance and decrease the friction coefficient of the Ni60 coating, while it led to a transformation of the micro-plowing and micro-peeling wear modes of the Ni60 coating to micro-plowing.