The Tribological Property and Microstructure of Ni-Ti Coating Prepared by Electrodeposition and Heat Treatment

Ni-Ti coatings were fabricated by the electrodeposition in a Ni plating bath containing Ti power and heat treatment in nitrogen atmosphere. The surface morphology and microstructure of the Ni-Ti coating before and after heat treatment were analyzed by means of scanning electron microscopy and X-ray diffraction. The friction and wear behaviors of two different coatings were evaluated on a ball-on-disk UMT-2MT test rig. It was found that the phase structure of Ni-Ti coating heated in nitrogen was much different from that of the as-deposited Ni-Ti coating. Namely, the new intermetallic compounds, including Ni3Ti, NiTi, and NiTi2, and TiN were detected in the coating after heat treatment by the XRD analysis and contributed to greatly increasing the hardness and tribological property of the Ni-Ti coating, owing to the strengthening effect of the hard intermetallic compounds and TiN phase. At the same time, a small amount of intermetallic compounds and TiN was transferred from the composite coating to the rubbing surface of the counterpart steel ball during the sliding, which also contributed to decreasing the friction coefficient and increasing the wear resistance.