Comparative analysis on the microstructure and property of Ni-based coatings remelted by laser and flame

摘要

Ni60 coatings have been prepared by flame spraying and flame remelting process and by flame spraying and laser remelting process on the surface of low-carbon steel (Q235) respectively. The developed Ni60 coatings were characterized by using scanning electronic microscope (SEM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and micro-hardness tester. Corrosion resistance of the coatings was measured using corrosion weight loss method. The results show that the microstructure of laser remelted coatin gs contains fine grains and a large number of dendrites. However, the microstructure of flame remelted coatings contains coarse massive grains. In both flame remelted and laser remelted coatings the white-bright dendrites consist of γ-(FeNi) solid solution, and grey matrix between dendrites consist of the eutectic of γ-(FeNi) and Cr _7C _3, CrB, Ni 3B. In addition, grey matrix between dendrites for flame remelted coatings contains the oxide phases, such as Cr _2O _3, NiCr _2O _4, Fe _2O _3. The even hardness of flame remelted coatings is higher than that of laser remelted coatings, but its hardness distribution is non-uniform. And corrosion resistance in sulfuric acid solution of laser remelted Ni60 coatings is superior to that of flame remelted coatings.