1.State Key Laboratory for Mechanical Behavior of Materials, Xi‘an Jiaotong University, Xi’an 710049, China
2. Institute of New Materials, Guangdong Academy of Science, Guangzhou 510650, China
Environmental barrier coatings (EBCs) are crucial for the application of silicon carbide fiber-reinforced silicon carbide ceramic matrix composites (SiCf/SiC CMCs) in hot end components of aircraft engines. However, during the coating preparation process, it is difficult to avoid surface cracks and pores, which become rapid diffusion channel for corrosive media such as water and oxygen in the engine environment. Therefore, preparing densified EBCs is the key to improve SiCf/SiC CMCs corrosion resistance. Additionally, to ensure durability under cycling conditions with the high and low temperature changes,distinguished thermal cycling resistance is essential for EBCs. This study used the method of aluminum-infiltration to obtain densified EBCs, and investigated the structural evolution of the coating under 1050 ℃~room temperature thermal cycling, revealing the influence mechanism of densification treatment on the thermal cycling resistance of the coating. The results indicated that the aluminum-infiltration-densified method eliminated the surface exposed pores of the sprayed EBCs and formed an in-situ reaction layer of ytterbium aluminum garnet (YbAG) on the surface. During the thermal cycling process, the internal stress of the sprayed EBCs gradually accumulated, resulting in an increase in the number of vertical cracks and a decrease in crack spacing. The heat treatment of aluminum-infiltration process significantly increased the internal stress of EBCs, promoting early crack growth and propagation, the number and spacing of cracks were comparable to those of sprayed EBCs after 200 thermal cycles, and no new or extended cracks were observed during the thermal cycling. Therefore, this study provides experiment data support for the preparation of thermal cycling resistant aluminuminfiltration-densified EBCs.