Oxidation behavior of Cr1-xAlx coated Zr-4 alloy under 1200 °C high temperature steam environment

In present study, the 1200 °C high temperature steam (HTS) oxidation behavior of Cr1-xAlx coating with different Al content (0, 35 at.%, 50 at.% and 70 at.%) deposited on Zr-4 alloy by multi-arc ion plating (MAIP) has been investigated. The results demonstrate that Cr65Al35 coating has optimal protectiveness due to the formation of compact and continuous double oxide layer, consisting of outer Al2O3-rich layer and inner Cr2O3-rich oxide layer. The severe consumption of Al element for Cr50Al50 coating during the oxidation process, leading to vacancies formation and a decrease in enrichment degree of the Al2O3 in outer oxide layer. The protectiveness of pure Cr coatings is reduced by the formation of volatile CrO3, which induces the micro voids and provides a channel for the oxygen diffusion. The Cr30Al70 coatings shows the worst protective effect because of the serious diffusion behavior of Al into Zr alloy, providing the diffusion channel for O element and causing the substrate to oxidize essentially. The effect of Al content on the oxidation resistance of Cr1-xAlx coatings is discussed in detail.