CVD法硅改性铝化物复合涂层工艺及性能研究

发布时间：2018-05-05 11:43

  本文选题：Si改性铝化物涂层 + CVD　； 参考：《机械科学研究总院》2015年硕士论文

【摘要】：航空发动机涡轮叶片通常采用化学气相沉积(CVD)法在内腔和外表面涂覆一层单一铝化物涂层,以降低叶片的高温腐蚀。但这种铝化物涂层抗热腐蚀性能较差,长期在高温中服役时,涂层会与基体合金元素会发生互扩散,造成涂层中铝含量降低,最终导致涂层表面不能形成连续致密的氧化铝保护膜,涂层即失去保护作用。通过向单一铝化物涂层中加入改性元素形成改性铝化物扩散障涂层,可明显提高涂层的抗高温氧化性能和抗热腐蚀性能,进而提高航空发动机涡轮叶片的使用寿命。本文使用CVD法沉积+扩散复合处理工艺对前期试验制备的单一铝化物涂层进行了优化,处理后涂层中的元素扩散得较为充分,涂层组织均匀,同时,涂层厚度会有一定程度的增加,内层占涂层厚度比例发生变化,涂层呈现不同的结构。通过铝化物沉积+扩散复合处理工艺前后涂层成分、组织结构变化,本文对CVD法沉积+扩散复合处理工艺下单一铝化物涂层形成过程进行了研究。在对CVD法单一铝化物涂层制备工艺和形成过程深入认识的基础上,本文系统地研究了CVD法Si改性铝化物涂层制备工艺,发现一步Al-Si共沉积工艺可控性差,涂层中元素出现相间分布的特殊情况;两步法中先沉积Al后沉积Si会导致硅化物替代铝化物的情况发生;先沉积Si后沉积Al可较容易地制备出外层富Al内层富Si的双层结构涂层,外层与内层通过冶金结合,涂层结构合理。因此,选择CVD法先沉积Si后沉积Al工艺制备硅改性铝化物涂层,进而研究采用CVD法先沉积Si后沉积Al+扩散复合处理工艺,与无扩散处理的硅改性铝化物涂层相比,涂层厚度增加,在外层与内层之间出现富Al的中间层,涂层成分分布、组织更为均匀。本文进行了1100℃温度下60h的高温氧化试验,结果表明Si改性铝化物复合涂层表现出比单一铝化物涂层更为优异的抗高温氧化性能。在高温氧化过程中单一铝化物涂层中的Al含量降低;Si改性铝化物复合涂层中Si对Al的内扩散起到了很好的阻挡作用。在高温氧化过程中,Si改性铝化物涂覆试样和单一铝化物涂覆试样都先后经历增重较快的氧化初期阶段(0~20h)和增重较慢的氧化平稳阶段(20~60h)。
[Abstract]:In order to reduce the high temperature corrosion of aero-engine turbine blades, chemical vapor deposition (CVD) method is usually used to coat the inner and outer surfaces with a single aluminized coating. However, the thermal corrosion resistance of the aluminized coating is poor. When the coating is in service at high temperature for a long time, the coating will interdiffusion with the alloy elements of the substrate, resulting in the decrease of the aluminum content in the coating. Finally, the coating surface can not form a continuous dense aluminum oxide protective film, the coating will lose its protective effect. By adding the modified elements into the single aluminized coating to form the modified aluminum diffusion barrier coating, the high temperature oxidation resistance and thermal corrosion resistance of the coating can be improved obviously, and the service life of the aero-engine turbine blade can be improved. In this paper, the single aluminized coating was optimized by CVD deposition and diffusion process. After the treatment, the elements in the coating were diffused more fully, the structure of the coating was uniform, and the structure of the coating was uniform, at the same time, The coating thickness will increase to a certain extent, the ratio of inner layer to coating thickness will change, and the coating presents different structure. In this paper, the formation process of single aluminized coating under CVD deposition and diffusion composite treatment was studied by changing the composition and structure of the coating before and after the deposition and diffusion composite treatment of aluminides. Based on the deep understanding of the preparation process and formation process of single aluminum oxide coating by CVD method, the preparation process of Si modified aluminum oxide coating by CVD method is systematically studied. It is found that the one-step Al-Si co-deposition process is not controllable. In the two-step method, the deposition of Al and then the deposition of Si will lead to the occurrence of silicides instead of aluminides. It is easy to prepare Si-rich bilayer structure coatings with Al-rich inner layer by deposition of Al and then Al. The structure of the coating is reasonable by metallurgical bonding of outer layer and inner layer. Therefore, Si-modified aluminized coating was prepared by CVD method and then deposited by Al process, and then the CVD method was used to deposit Si and then deposited Al diffusion composite coating, which was compared with the silicon-modified aluminized coating without diffusion treatment. With the increase of coating thickness, there is an Al rich interlayer between the outer layer and the inner layer, the composition of the coating is distributed and the microstructure is more uniform. The high temperature oxidation test at 1100 鈩，

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