Pulsed laser remelting supersonic plasma sprayed Cr3C2-NiCr coatings for regulating microstructure, hardness and corrosion properties

Abstract

Abstract Supersonic atmosphere plasma sprayed Cr3C2-NiCr coatings have been gradually used for protecting industrial components from the severe wear and corrosion attack. In this study, the pulsed laser technique was applied to remelt the deposited Cr3C2-NiCr coatings. The evolution in microstructure and corrosion resistance between the as-sprayed coating and pulsed laser remelted coating was carefully investigated. It is found that desirable metallurgical bonding was achieved between the pulsed laser processed coating and the substrate. After pulsed laser remelting treatment, the metastable phase disappeared and the coating was composed of equilibrium phases of Cr7C3 and Ni-crystal. Interestingly, the morphology of the newly formed carbides became regular and the high-speed Marangoni flow inside the molten pool facilitated their homogeneous distribution. Overall, the porosity decreased from 4.3% of the as-sprayed coating to 1.1% of the laser-treated coating while the carbide volume fraction increased from 49% to 70%. Due to that the coating microstructure became more homogeneous and denser after pulsed laser remelting, the hardness and corrosion resistance were greatly improved.