Effect of Power on Salt Spray Corrosion and Electrochemical Corrosion of Laser Thermal Sprayed Cr3C2–NiCr Coatings
H-Y. Wu and D-J. Kong
Cr3C2–NiCr composite coatings were fabricated on H13 hot worked mould steel using a fibre laser thermal spraying at various laser powers. The surface and cross-section morphologies, chemical compositions and phases in the laser thermal sprayed Cr3C2–NiCr composite coatings were analysed. The effects of laser power on the salt spray corrosion and electrochemical corrosion of the laser thermal sprayed Cr3C2–NiCr composite coatings in 3.5% NaCl solution were investigated. The results show that the laser thermal sprayed Cr3C2–NiCr composite coatings are primarily composed of Cr7C3 and Cr3C2 hard phases, accompanied with the Ni–Cr binder phase. Laser power was found to have no effect on phase compositions, which retain the coating integrities due to their double layer passivation films. The self–corrosion current densities of the laser thermal sprayed Cr3C2–NiCr composite coating fabricated at laser powers of 1200, 1400, 1600 W were 17.47, 9.5850, and 24.83 μA/cm2, respectively; and the corresponding transfer resistances were 529.6, 1136, and 846.7 Ω•cm2, respectively; showing that the electrochemical corrosion resistant of the laser thermal sprayed Cr3C2–NiCr composite coating fabricated at the laser power of 1400 W performed the best.
Keywords: Fibre laser, H13 hot worked mould steel, Cr3C2–NiCr composite coating, laser thermal spraying, laser power, microstructure, phase, salt spray corrosion, electrochemical corrosion