Comparative study on high-temperature performance and thermal shock behavior of plasma-sprayed Yb2SiO5 and Yb2Si2O7 coatings

In this work, differences of microstructure and thermo-mechanical properties between air plasma sprayed Yb2SiO5 and Yb2Si2O7 coatings were investigated. Thermal shock behavior between Yb2SiO5/Si and Yb2Si2O7/Si EBC systems on SiC substrates were compared. Results show that the Yb2Si2O7 coating exhibited significant microstructure evolution compared to Yb2SiO5 during high temperature thermal aging, which is attributed to the different activation energy of grain growth between the Yb2SiO5 (366 kJ/mol) and Yb2Si2O7 (219 kJ/mol) coatings. The Yb2Si2O7 coating exhibited lower CTEs, elastic modulus and hardness, however, higher thermal conductivity compared to the Yb2SiO5 coating. After thermal shock test for 40 cycles, partial delamination occurred in the Yb2SiO5/Si system, while the Yb2Si2O7/Si system remained integral. The failure mechanism of these rare-earth silicates EBC systems were analyzed in detail. The results of this study may provide a reference for EBCs design and applications.