Effect of electron beam remelting on microstructure and wear properties of HVOF Ni/WC coatings

Abstract

In order to improve the wear resistance of Inconel 617 alloy, Ni/WC composite coatings were prepared on it by High-Velocity Oxygen Fuel (HVOF) and electron beam remelting techniques. The effects of remelting beam current (16 mA–25 mA) on the macroscopic morphology, physical phase composition and microstructure of remelted coatings were investigated. The effect of microcomposition on the mechanical properties of remelted coatings was analyzed in combination with hardness tests and friction wear experiments. The experimental results showed that good metallurgical bonding was formed for 19 mA, 22 mA and 25 mA specimens after electron beam remelting. The bonding of the 16 mA specimen was a combination of metallurgical and mechanical bonding. The remelted coating generated new phases such as W₂C, M₃B and Cr₂₃C₆. With the increase of remelting beam current, the WC decomposition became more and more serious, and the grain growth tendency was evident. The remelted coatings prepared with different parameters showed a significant increase in microhardness compared to both the substrate and HVOF coatings. Friction wear experiments with SiC balls as counterbodies show that the wear increases gradually with increasing beam flow at 100 N and under dry friction conditions. The wear mechanism of HVOF coatings was abrasive, and the wear mechanism of remelted coatings was mainly abrasive and adhesive. In summary, the 22 mA specimen had a strong metallurgical bond. The hardness and abrasion resistance were improved compared to the substrate and the HVOF coating, i.e., the 22 mA specimen had the best overall performance.