The Degradation of SA213-T22 steels Coated with Ni-based Alloy Containing WC-Co in Simulated Molten Salt Atmospheres

Abstract

This work reveals the high-temperature oxidation resistance of WC-Co coated on SA213-T22 by High-Velocity Oxy-Fuel (HVOF) technique in simulated molten salt atmospheres and compare that with the uncoated Cr-containing steel. The corrosion behaviors of SA213-T22 coated and uncoated with WC-Co alloys were studied by immersion test under simulated molten salt atmospheres at 600 °C for 3 hours and investigated their corrosion current densities by electrochemical test. Scanning electron microscope equipped with EDS technique and X-ray diffraction were used to evaluate the surface morphology and phase constitution. The oxidation rate of the coated and uncoated steels was observed under simulated atmospheres at 750 °C for 120 hours before the immersion test. The mass gain scale increase with increasing the oxidation time and the oxidation rate of scale are limited by the WC-Co alloys coating layer, which acted as a protective layer. The low corrosion current density of the WC-Co self-fluxing coated steel after oxidation was shown 5 – 10 μA/cm 2 after the corrosion test in molten salt for 3 hours. After the immersion, the scale layer on the uncoated specimen was disappeared, but one-half of the oxidized coating layer on the coated specimen has remained.