Al-Cr涂层对TC21合金抗氧化和热腐蚀性能的影响

Effect of Al-Cr coating on oxidation and hot corrosion resistance of TC21 alloy

采用双辉等离子表面渗铬和后续多弧离子镀铝处理在TC21合金表面制备Al-Cr涂层;同时研究Al-Cr涂层在850℃下的高温氧化行为和850℃下25%NaCl+75%Na_2SO_4(质量分数)混合盐中的热腐蚀行为。结果表明:Al-Cr复合涂层包括表面富Al沉积层、中间Al-Cr扩散层和内侧Cr-Ti互扩散层。在850℃氧化100 h后,Al-Cr涂层表面生成致密Al_2O_3膜,对基体有很好的保护作用;中间Al-Cr扩散层中Cr元素的存在促进Al的选择性氧化,有利于涂层的后续氧化行为。在850℃混合熔盐中腐蚀100 h后,内部Cr-Ti扩散区仍保持完整,涂层表现出较好的热腐蚀抗力。

Cr＋Al-type（Al-Cr） composite coating was prepared by double glow plasma surface chromizing on TC21 substrate followed by multi-arc ion aluminizing. The oxidation behaviors of Al-Cr coating in air and in mixed salt （25%NaCl＋75%Na2SO4, mass fraction） at 850 ℃ were tested, respectively. The results demonstrate that Al-Cr coating consists of an outer layer of Al-rich deposition, an intermediate Al-Cr diffusion layer and an inner Cr-Ti mutual diffusion zone. After oxidation at 850 ℃ for 100 h, a dense Al2O3 oxide layer forms in the external oxide film, which provides protection for the substrate. As for the Al-Cr diffusion layer, the presence of Cr can promote the selective oxidation of Al, which is beneficial for improving the oxidation resistance. After 100 h exposure in mixed salt at 850 ℃, the inner Cr-Ti mutual diffusion zone is still integrated, indicating that Al-Cr coating has relatively good hot corrosion resistance.