Effect of Pulse Frequency on Microstructure, Friction and Wear Properties of Inconel 718 Coatings Prepared via Laser Cladding

Abstract

The Inconel 718 alloy clad coating was successfully prepared via pulsed laser deposition. The effect of pulse frequency on the evolution of microstructure, hardness and tribological properties of the as-deposited samples were analyzed via scanning electron microscopy (SEM), microhardness tester and ball-on-plate tribometer. The results showed that with the decrease in pulse frequency, the cooling rate of molten pool increases gradually, which effectively refines the γ-(Ni, Cr, and Fe) dendrites and restrains Nb segregation. Hence, the morphology of the brittle Laves phase changed from long chained to granular and its volume fraction decreased from 6.59% to 2.41%. The hardness of the coating increased from 261 HV0.1 to 297 HV0.1 and the tribological property also improved simultaneously. The friction coefficient decreased from 0.2387 to 0.2066, and the wear rate decreased from 27.30 × 10−4 mg·N−1·m−1 to 19.15 × 10−4 mg·N−1·m−1. It can also be observed that the wear area of the counterpart, Si3N4 ball, increased from 2.016 mm2 to 2.662 mm2. The increase in the hardness and tribological property were attributed to the grain refining strengthening.