采用等离子喷涂工艺在TiAl基合金表面制备NiCoCrAl-Y2O3涂层,并用激光重熔工艺对涂层进行处理。用SEM、XRD对激光重熔前后的试样进行检测,分析了涂层的微观组织结构以及物相成分组成,同时对涂层进行高温氧化试验。结果表明,等离子喷涂后的涂层组织较致密,但仍存在孔洞等缺陷。激光重熔后涂层的组织结构进一步均匀、致密,晶粒得到细化。激光重熔过程中,涂层中Al元素上浮,并部分氧化生成Al2O3相。这两方面均可有效“阻碍”氧离子向内扩散和金属阳离子向外扩散,使重熔后涂层的高温抗氧化性能得到较大地改善。
An experiment of laser remelting was carried out to process NiCoCrAI-Y2O3 coatings on TiAl alloys which had been prepared by plasma spraying. Microstructure and phase components of plasma sprayed and laser remehed NiCoCrAl-Y2O3 coatings were investigated using scanning electron microscopy and X-Ray Diffraction. Meanwhile, the high temperature oxidation resistance of the coatings was studied respectively. The results show that the plasma-sprayed coating had some defects, those distributed holes for example, although its microstructure was rather compact. However, the laser-remelted coating had more compact microstructure, with its grain refined greatly. Aluminium element of the coating floated upward and was oxidized part- ly. Both of the two factors can improve performance of the laser remehed coatings obviously by hindering inward diffusion of oxygen ion and outwards diffusions of metal cation.