Zr-2合金表面ZrO_(2)/Cr复合膜的高温蒸汽氧化行为

High Temperature Steam Oxidation Behavior of Zr-2 Alloy with ZrO_(2)/Cr Composite Coating

用微弧氧化(MAO)和磁过滤阴极真空弧离子镀(FCVAD)在Zr-2合金表面制备ZrO_(2)/Cr复合膜,用热重分析仪(TGA)评估了Zr-2合金基体和ZrO_(2)/Cr复合膜在900~1100℃蒸汽环境中的抗氧化性能,并分析其氧化后氧化层的截面结构、相组成和成分深度分布。结果表明,在900、1000和1100℃蒸汽环境中分别氧化3600 s后,ZrO_(2)/Cr复合膜试样单位面积增重约为Zr-2合金基体的3/8、1/4和2/5。在高温蒸汽环境中,ZrO_(2)/Cr复合膜表面氧化生成的致密Cr_(2)O_(3)膜能抑制氧向内扩散,提高锆合金的抗蒸汽氧化性能,阻止锆试样在1000℃蒸汽环境中出现分离氧化。ZrO_(2)/Cr复合膜的表面Cr层完全消耗前,Cr涂层的氧化主要取决于铬向外扩散,而不是氧向内扩散。在蒸汽氧化过程中,MAO膜的中间层能抑制氢渗透进入锆合金基体。

A ZrO_(2)/Cr composite coating on Zr-2 alloy was prepared by micro-arc oxidation(MAO)and filtered cathodic vacuum arc deposition(FCVAD)treatments.The oxidation resistance of bare and ZrO_(2)/Cr-coated Zr alloys was estimated in 900~1100°C steam environment using a thermogravimetric analyzer(TGA)and their cross-sectional structures,phase constituents and composition depth profiles before and after steam oxidation were analyzed.The results showed that the mass gain per unit area of ZrO_(2)/Cr-coated Zr alloy was about 3/8,1/4 and 2/5 of that of bare Zr alloy after 3600 s steam oxidation at 900,1000 and 1100℃,respectively.In high temperature water vapor,the dense Cr_(2)O_(3) film formed on the surface of ZrO_(2)/Cr-coated one suppressed the inward oxygen diffusion,which improved the steam oxidation resistance of Zr-2 alloy and inhibited the occurrence of breakaway oxidation at 1000℃.Before the Cr layer of ZrO_(2)/Cr composite coating was completely oxidized into Cr2O_(3),the oxidation of Cr layer was principally controlled by the outward chromium diffusion rather than inward oxygen diffusion.The MAO interlayer restrained hydrogen permeation into Zr alloy substrate during the steam oxidation.