Microstructure evolvement and wear properties of Ni60-based coating by ultrasonic power-assisted laser cladding

Abstract

Ultrasonic vibration is known to cause significant refinement of microstructure, the effect of ultrasonic power on grain size, grain orientation and Schmid factor by laser cladding in the Ni60/WC composite coating was studied systematically. Meanwhile, the effect of microstructure on wear properties and hardness was elucidated. The results show that the performance of the cladding layer is the best when the ultrasonic power is 600 W, which is due to the combined effect of ultrasonic cavitation and acoustic flow. The average grain diameter is refined from 28.36 μm to 23.02 μm, and the refinement range is 18.9%. The formation of low Angle grain boundaries (LAGBs) is promoted by ultrasound, and the dislocation density is increased. The texture strength of the coating is distributed over {100}, {110} and {111} surfaces, and the strength decreases from 12.307 to 5.447 The microhardness is increased by 16% (from 768.85HV1 to 896.95HV1), the wear mechanism gradually from adhesive to abrasive wear and the average friction coefficient decreases from 0.47 to 0.216 with the increase of ultrasonic power, which improve the wear resistance of the coatings. Based on the understanding of microstructure evolvement, the grain refinement mechanism effected by ultrasonic power was explained from the aspect of cavitation processes.