Corrosion Behaviors of ZrSi Coating by Laser Cladding on Zr-4 Alloy in High-Temperature Steam

Si powder was deposited onto the surface of Zr-4 alloy via laser cladding to enhance its high-temperature oxidation resistance. The high-power laser radiation and rapid solidification lead to a reaction between Si and Zr, resulting in the formation of a microstructure consisting of lath-like ZrSi2 and Si-rich phases. The oxidation behavior of the laser-cladding ZrSi coating was evaluated at 1100–1300 °C in water steam. The weight gain follows a parabolic law, and the oxidation activation energy of the ZrSi coating is 182.7 kJ mol−1. The oxides produced by ZrSi2 oxidation are mainly ZrSiO4, ZrO2, and SiO2, and, under high-temperature conditions, the relative content of ZrSiO4 in the oxide decreases with increasing temperature. The oxidation of the ZrSi2 phase induces significant growth stresses, which are susceptible to causing cracks in the oxide, facilitating accelerated oxygen diffusion into the coating. However, the amorphous SiO2 formed at 1300 °C, which may be softened and fluidized to enable a self-healing effect, can heal the cracks to diminish oxygen permeation into the coating, improving its oxidation resistance. The oxidation resistance of the laser cladding ZrSi coating is better than that of the Zr-4 alloy.