Influence of the grain size on CMAS attack of Sm2Zr2O7 ceramic

Abstract The temperature resistance of thermal barrier coatings (TBCs) has increased with the continuous development of the aviation industry. This increase in temperature resistance has resulted in a new challenge for TBCs, namely, calcium-magnesium-aluminum-silicate (CMAS) attack. As a new generation of thermal barrier coating candidate materials, Sm2Zr2O7 has good CMAS resistance properties. However, this material cannot meet the actual needs of aero-engines. Therefore, a change in the structure of Sm2Zr2O7 was used to improve the CMAS resistance properties in this paper. The relationship between the grain size of the ceramic and its resistance to CMAS penetration in the microstructure was investigated in detail. Nonpressure and SPS sintering processes were used to prepare Sm2Zr2O7 ceramics with different grain sizes that were then tested at high temperatures with CMAS. With the extension of penetration, the depth of CMAS penetration in microscale Sm2Zr2O7 ceramics increased sharply with increasing reaction time, while the penetration depth of CMAS into nanoscale Sm2Zr2O7 ceramics increased slowly. After 48 h of penetration, the penetration depth of the microscale Sm2Zr2O7 ceramics was 86 μm, and the penetration depth of the nanoscale Sm2Zr2O7 ceramics was only 47 μm. Compared with the microscale Sm2Zr2O7 ceramics, the nanoscale Sm2Zr2O7 ceramics had better CMAS resistance because the lower diffusion activation energy of the nanocrystalline grains accelerated the formation of a dense barrier layer.