Microstructure and wear behaviors of WC-Ni coatings fabricated by laser cladding under high frequency micro-vibration

WC-Ni composite coatings were fabricated on Ti-6Al-4V alloy substrates by laser cladding under high frequency micro-vibration. The microstructure, phase composition, microhardness and wear resistance of the cladding coatings were investigated by X-ray diffractometer (XRD), scanning electron microscope (SEM), energy disperse spectroscope (EDS), microhardness tester and friction and wear testing apparatus, respectively. The high frequency micro-vibration produced by a vibration exciter system made of magnetostrictive materials was used to assist laser cladding of nickel composite coatings. The effects of high frequency micro-vibration on the microstructure and properties of the cladding coatings are investigated. The results showed that high frequency microvibration promoted the formation of W2C and (Ti, W) C during the laser cladding process. Alloying carbide with rich tungsten is uniformly distributed in eutectic (Ti) Ni solid solution under the vibration frequency of 556 Hz, with some new W2C phases generated in the composite coating. In addition, at the bonding interface, the number of coarse dendrites is continuously reduced and that of fine grains is gradually increased. Appropriate increase of vibration frequency contributes to the refinement of the grains. The vibration makes the coating microstructure more uniform, which helps to reduce the microhardness fluctuation in the cladding coating. With the help of the fine-grained hard phase, the microhardness of the cladding coating is enhanced by the vibration. By choosing appropriate vibration parameters, high frequency micro-vibration helps to decrease the friction coefficient and wear loss of the composite coating.