Study Of Nickel-based Coatings Prepared By Spraying And Remelting Process On Aluminum Bronze

In order to improve the corrosion resistance and wear resistance of traditional castaluminum bronze alloy, firstly, this paper adopted oxygen-ethyne flame sprayingtechnology to prepare Ni60and Ni60WC25two kinds of coatings deposited on the surfaceof aluminum bronze, and then remelted on two kinds of coatings by high frequencyinduction remelting technique. The surface morphology, microstructure, microhardness,corrosion resistance and wear resistance were investigated. The effects of spraying andremelting technological parameter on the experimental process were also investigated, andthe mechanism of improving the coating properties was discussed.The results showed that the nickel coatings prepared by spraying and remeltingmethod could improve the corrosion resistance and wear resistance of aluminum bronze’ssurface. Ni60and Ni60WC25two coatings prepared by flame spraying method had roughsurface, lamellar structure, more defects, and formed mechanical bond with substrate. Afterinduction remelting, remelting coatings had smooth surface, compact and uniform structure,and formed higher strength metallurgical bonding with substrate.Ni60spraying and remelting coatings’ organization had no essential difference. Ni60remelting coating had no Cr₃C₂phase, and the other phase consisted of Ni-based solidsolution, Cr₇C₃, Cr₂₃C₆, Cr₂B, Ni₃B, Ni₃Fe. The organization of Ni60WC25spraying andremelting coatings did not change. Ni60WC25remelting coating increased Ni₂W₄C phase,and the other phase consisted of Ni-based solid solution, Cr₇C₃, Ni₃Fe, B_0.7Fe₃C_0.3, WC,W₂C, Ni₃Si₂. Ni60spraying and remelting coatings, Ni60WC25spraying and remeltingcoatings all had good thermal shock resistance.The average corrosion weight loss rate of Ni60remelting coating was less thanspraying coating and substrate in the static immersion. The corrosion potential of Ni60remelting coating was bigger than spraying layer and substrate, and Ni60remelting coatinghad smaller corrosion current. Therefore, the corrosion resistance of Ni60remeltingcoating was best. The corrosion mechanism of substrate was components selectivecorrosion, while the corrosion mechanism of Ni60spraying and remelting coatings did notbelong to the components selective corrosion. The corrosion potential of Ni60WC25spraying and remelting coatings were bigger than substrate, and their corrosion current wassmaller than substrate. But the corrosion potential of Ni60WC25coatings were less thanNi60coatings, and their corrosion current was bigger than Ni60coatings. Consequently,the corrosion resistance of Ni60WC25coatings was stronger than substrate, weaker thanNi60coatings. Due to B, Si elements’ deoxy slagging effect, Ni60remelting coating’s microhardnesswas slightly less than spraying coating, but higher than substrate, and uniformly distributed.The microhardness of Ni60WC25spraying and remelting coatings were both higher thanthe corresponding Ni60coatings, and played a role of surface strengthening effect. Thefriction coefficient of Ni60remelting coating and Ni60WC25remelting coating werestable and lower than the corresponding spraying coating, and had good anti-frictionproperties. Ni60remelting coating’s wear volume was smaller than substrate and sprayingcoating, and showed good wear resistance. Thanks to the strengthening effect of WC hardparticles, Ni60WC25remelting coating’s wear volume was smaller than Ni60remeltingcoating, and had the best wear resistance. The wear mechanism of aluminum bronzesubstrate was adhesive wear and spalling wear. The wear mechanism of Ni60remeltingcoating was slight wear of adhesive wear. The wear mechanism of Ni60WC25remeltingcoating was abrasive wear.