镍基合金上化学气相沉积铝涂层的试验研究

Experimental Study of Chemical Vapor Deposition Aluminizing Coatings on Ni-Based Superalloy

镍基高温合金表面渗铝是提高材料抗高温氧化和耐热腐蚀性能的一种普遍适用的方法。以燃气轮机中常见的镍基高温合金K444为基体做CVD渗铝工艺,采用特殊的工装来模拟涡轮叶片内外腔同时渗铝的状况,并对比热处理前后的涂层厚度及元素变化。结果表明:工艺气体流速越慢则涂层平均厚度越大,但沿着气流方向的厚度差异也越大;内腔的涂层厚度大于外腔的涂层厚度,但外腔的涂层均匀性更好;热处理后涂层外层生长出新的NiAl层,涂层总厚度增加了2~10μm,扩散层占总涂层比例从平均30%下降到了27%,外层铝含量从平均27%下降到18%。最终涂层呈现出典型的低活性渗铝涂层的形貌。研究成果可为涡轮叶片渗铝涂层的工艺开发提供参考。

Surface aluminizing on Ni-based superalloy is a common method to improve the high temperature anti oxidisability and corrosion resistance properties. The Ni-based K444 used as the general gas turbine blade material was applied to CVD aluminizing as a substrate. A special fixture was employed to simulate the condition of aluminizing on both internal structure and outside profile of turbine blade. The coating thickness and element change were then compared before and after heat treatment. The results showed that coating thickness of internal structure was thicker than that of outside profile, but outside profile coating had better thickness uniformity. A new NiA1 layer grew out on the outer layer of caating after heat treatment. The total thickness had an increase of 2-10μm, diffusion layer of total coating declined from an average of 30% to 27%, and outer layer AI element content decreased from an average of 27% to 18% after heat treatment. Finally, the coating showed a typical morphology of low active aluminizing coatings. This research can provide reference for the aluminizing coating process of turbine blades.