Microstructure and wear resistance of Inconel 718 alloy coating repaired by microwave heating remanufacturing

• Propose a novel microwave heating remanufacturing technique to repair IN718 alloy. • MHR coating shows a gradient distribution with dendritic, cellular and Laves phase. • Wear resistance of MHR coating is greatly improved by more than 50%. • Top dendrites can withstand heavy load and fish-scale layer can store wear debris. A novel microwave heating remanufacturing (MHR) technology is proposed in this paper, and the Inconel 718 nickel-based superalloy coating is successfully prepared at the groove of substrate. The MHR coating shows the low porosity with only 2.8 % and its microstructure has gradient distribution feature, in which the upper layer is dominated by dendrites, and a large number of chromium carbide hard phases appear in this region. The middle layer of the powders undergoes four microwave heating stages of “micro-melting, necking, liquefaction, filling” to form cellular crystals, accompanied by a large number of quasi-continuous network-like carbide precipitation as the enhanced skeleton. The lower layer produces the chain-like Laves phase under the effect of heating. In addition, the microhardness of the MHR coating also shows the gradient distribution, gradually decreasing from 232 HV at the top to 210 HV at the bottom. The friction and wear experiments show that the average friction coefficient, the mass loss and the wear rate of MHR coating are 0.62, 7.1 mg, and 27.61 × 10 -6 mm 3 /(N·m), respectively, indicating the wear resistance is improved by more than 50 % compared to the substrate. The surface worn morphology shows that the dendrites on the top of MHR coating can withstand large normal load and transverse shear force. Besides, the fish-scale layered structure formed after dendrites bending can play a role of storing wear debris, which greatly improves the wear resistance of coating. The proposed MHR technology offers a completely new approach for the repair of parts and components.