为了进一步提高TiAl合金的耐热腐蚀性能,分别采用等离子喷涂和等离子喷涂-激光重熔复合工艺在TiAl合金表面制备了纳米Al2O3-13%TiO2(质量分数)陶瓷涂层,研究了两种涂层在850℃下75%Na2SO4+25%NaCl(质量分数)熔融盐中的热腐蚀行为,用扫描电子显微镜(SEM)和X射线衍射仪(XRD)对腐蚀后试样的微观组织以及物相进行了分析,并讨论了激光重熔处理对涂层耐热腐蚀性能的影响。结果表明,等离子喷涂陶瓷涂层的腐蚀情况较为严重,经过激光重熔后可以有效提高其耐热腐蚀性能。激光重熔试样具有较高抗热腐蚀性能的原因是:一方面激光重熔消除了喷涂层的层状结构和大部分孔隙,形成了均匀致密的重熔层,减少了热腐蚀过程中的腐蚀扩散通道;另一方面归因于激光重熔使亚稳相γ-Al2O3转变为稳定相α-Al2O3。

In order to improve the hot corrosion resistance of TiAl alloy, the nanostructured Al2O3-13%TiO2 (mass fraction) ceramic coatings were fabricated by the plasma spraying and plasma spraying-laser remelting technology on TiAl alloy surface respectively. The hot corrosion behavior of the coatings in molten 75%Na2SO4+25%NaCl (mass fraction) at 850℃ was investigated, and the microstructure and phase constitution of the corrode coatings were researched by scanning electron microscopy (SEM) and X-ray diffractometry (XRD) to inquiry the influences of laser remelting on the hot corrosion resistance of the plasma-sprayed ceramic coating. The result shows that the as-sprayed coating exhibited a quite serious corrosion and the laser-remelted coating had better hot corrosion resistance. One of the reasons for the improvement of hot corrosion resistance of remelted coating is the forming of a dense homogeneous remelted layer without voids, cavities and microcracks, which can hinder the diffusion of corrosion medium and protect the interior from corrosion. In addition, the metastable γ-Al2O3 phase in the remelted area transfers into stable α-Al2O3 phase also helps to improve the hot corrosion resistance.