Optimization of spraying process and stoichiometric stage of plasma‐sprayed Yb2Si2O7 environmental barrier coating

Abstract Ytterbium disilicate (Yb 2 Si 2 O 7 ) is a potential environmental barrier coating (EBC) material. In this paper, the microstructure and phase composition of plasma‐sprayed Yb 2 Si 2 O 7 coatings with different spraying process were systematically investigated to optimize the spraying power and spraying distance. Furthermore, in order to obtain Yb 2 Si 2 O 7 coating with single phase, a certain proportion of SiO 2 was added to the Yb 2 Si 2 O 7 powder to compensate for the volatilization of SiO 2 during plasma‐spraying process, and the influence of spraying powder composition on the microstructure and phase structure (composition and content) of Yb 2 Si 2 O 7 coatings were also characterized in detail. The results showed that the Yb 2 Si 2 O 7 coating was dense with fewer pores and cracks at the spraying power of 40 kW and the spraying distance of 100 mm. Yb 2 Si 2 O 7 coating with the “sandwich” structure was composed of Yb 2 Si 2 O 7 , Yb 2 Si 2 O 7 + Yb 2 SiO 5 , and Yb 2 SiO 5 three microstructures, which was mainly caused by the volatilization of SiO 2 in Yb 2 Si 2 O 7 spraying powder. The Yb 2 Si 2 O 7 coating contained 90.68 mol.% Yb 2 Si 2 O 7 phase and 9.32 mol.% Yb 2 SiO 5 phase after crystallization at 1300°C for 20 h. The coating was composed of Yb 2 Si 2 O 7 phase and amorphous phase after SiO 2 addition. Yb 2 SiO 5 phase precipitated from the coating after heat treatment at 1300°C, and its content decreased with the increase of SiO 2 content. The content of the Yb 2 Si 2 O 7 phase was as high as 99.41 mol.% when SiO 2 content was 10 mol.%, which would provide a scientific basis for further research on stoichiometric Yb 2 Si 2 O 7 EBCs with excellent properties.