Microstructure and Properties of Inconel 718 Coatings with Different Laser Powers on the Surface of 316L Stainless Steel Substrate

Abstract

Laser cladding is a new method to prepare coatings with good quality. Laser power is one of the main factors affecting the quality of laser cladding coatings. An appropriate laser power helps obtain a high-performance laser cladding coating. In order to obtain coatings with good quality, an experiment with different laser powers was designed in this research. Three Inconel 718 coatings with different laser powers were prepared on the surface of a 316L stainless steel substrate. And the effect of different laser powers (1400, 1600, and 1800 W) on the microstructure, phases, and element distribution of coatings (L1–L3) was investigated by SEM, EDS, XRD, and a wear and friction tester. Meanwhile, the microhardness and friction and wear properties of different coatings were analyzed. The results show that the coatings’ phases were the same and composed of γ~(Fe, Ni) solid solution, Ni3Nb, (Nb0.03Ti0.97)Ni3, MCX (M = Cr, Nb, Mo), and so on. The background zones in the L1–L3 coatings were mainly the Fe and Ni elements. The irregular blocks in the coating were rich in Cr, Mo, and Nb, which formed the MCX (M = Cr, Nb, Mo) phase. When laser powers were 1400, 1600, and 1800 W, the average microhardness of the three coatings was 685.6, 604.6, and 551.9 HV0.2, respectively. The L1 coating had the maximum microhardness, 707.5 HV0.2, because the MCX (M = Cr, Nb, Mo)-reinforced phase appeared on the upper part of the coating. The wear rates were 3.65 × 10−5, 2.97 × 10−5, and 6.98 × 10−5 mm3·n−1·m−1. The wear mechanism of the three coatings was abrasive wear and adhesive wear. When the laser power was 1600 W, the coating had the minimum wear rate, which exhibited the best wear resistance. When the laser power was 1600 W, the upper part of the coating to the bonding zone was mainly composed of equiaxed crystals, dendrites, cellular crystals, columnar crystals, and planar crystals. The fine crystals and compounds caused a decrease in wear volume, and they had the most optimal wear resistance.