Microstructure and wear resistance of a Ni-WC composite coating on titanium grade 2 obtained by electroplating and electron beam remelting

Abstract

To improve the hardness and wear resistance of titanium grade 2 (TA2), Ni-WC pre-coating by electroplating was prepared on the surface of TA2 substrate in advance, and then electron beam remelting was conducted. The microstructure of the coating was analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The SEM results showed that the coating was strongly attached to the TA2 substrate that and the Ti-Ni intermetallic compounds were evenly distributed with in the coating. Moreover, TEM results showed that WC did not undergo chemical decomposition during the remelting process and did not participate in the reaction of the Ti-Ni system. After electron beam remelting, the hardness significantly increased: the maximum Vickers hardness of the coating was 745 HV0.1, which was near 6 times higher than that of the TA2 substrate (approximately 130 HV0.1). A ball-on-disk wear test was carried out with the TA2 substrate and the coatings. The wear rates of the TA2 substrate and the coating were 7.034 × 10−4 and 2.596 × 10−5 mm3N−1 m−1, respectively. Thus, compared with the TA2 substrate, the coating notably improved the wear resistance.