Investigation on laser cladding high-hardness nano-ceramic coating assisted by ultrasonic vibration processing

Laser cladding Nickel–WC–CaF2 coatings with high hardness were prepared on medium carbon steel assisted by ultrasonic vibration processing. The microstructure, element distribution, phase composition and microhardness as well as wear resistance of the cladding coatings were investigated. It is found that ultrasonic vibration during laser cladding could reduce the degree of WC particle aggregation. The laser cladding Ni–WC–CaF2 coatings is composed of γ-(Fe, Ni) and WC particles while the cladding coating with ultrasonic vibration consists of γ-(Fe, Ni), Cr23C6, W2C and WC. In addition, the coarse dendrite has been replaced by some fine grain structure at the bonding interface. When the ultrasonic vibration power of 800 W is applied, the average microhardness of cladding coating increase to 1235HV0.1 resulted from the combined effect of refined grain, dispersion strengthening from hard WC phase and solid solution strengthening. And the wear mass loss and friction coefficient of Ni–WC–CaF2 coating are lower than the coating without ultrasonic vibration and the coating with the ultrasonic vibration power of 900 W. Especially, the worn mechanism on the surface is uniform ploughing.