Microstructure and property of Ni/WC/La2O3 coatings by ultrasonic vibration-assisted laser cladding treatment

Abstract

Ultrasonic vibration was introduced during laser cladding Ni-60%WC-0.8%La2O3 coatings in this study. The microstructure, elemental distribution, and properties of the cladding coatings, as well as the morphology of WC particles were also investigated. Results showed that with WC ceramic particles, the columnar dendrites that formed at the bottom of the cladding coating without ultrasonic vibration were dissolved, crystallized, and aggregated. As ultrasonic vibration was introduced, the dendrites in the cladding coating were disrupted, and the grains were refined. WC particles concentrated at the bottom of the cladding coatings at an ultrasonic power of 600, 700, and 900 W, resulting in obvious degradation in surface hardness and wear resistance. However, when an ultrasonic power of 800 W was applied, improved hardness and wear resistance, which are attributed to the strengthening of precipitated carbides, refined microstructure, and homogenous distribution of WC particles in the cladding coatings, were observed . For laser cladding coatings without ultrasonic vibration, typical characteristics of abrasive and fatigue wear could be found on the wear tracks after a ring-on-disk (ROD) wear test, and flaking pits appeared along the sliding direction. For the composite coatings prepared with different ultrasonic vibration power, typical abrasive wear occurred on the surfaces of the coatings under 600, 700, and 900 W during ROD wear tests, with additional shallow and mild ploughing for that under 800 W.