Effect of Yb_2Si0_5 Ceramic Layer Thickness on the Thermal Cycling Life of Yb_2SiO_5/LaMgAl_(11)O_(19) Coating Deposited on C/SiC Composites

摘要

C/SiC composites were plasma sprayed with Yb_2SiO_5/LaMgAl_(11)O_(19) (LMA) coatings with varying Yb_2SiO_5 layer thickness. The effect of Yb_2SiO_5 layer thickness on the thermal cycling life of the Yb_2SiO_/LMA coatings was investigated. The results showed that the thermal cycling life is significantly dependent on the Yb_2SiO_5 layer thickness. It decreased from 130 cycles to 35 cycles as Yb_2SiO_5 layer thickness increased from 50 μm to 100 μm. Further increasing Yb_2SiO_5 layer thickness to 200 urn made it decrease to 2 cycles. The influencing mechanism of Yb_2SiO_5 layer thickness for the thermal cycling life was clarified based on the thermal expansion behavior, the chemical stability at high temperature and the microstructure analysis.