Effects of mullite/YSZ coatings on the performance of SiC/ SiC composite combustion liners

Silicon carbide/ Silicon carbide (SiC/ SiC) woven composites were covered with plasma-sprayed mullite/ ZrO_2(-) 8 wt % Y₂O₃ coatings. Isothermal soaking in an oxidative environment was used to simulate a combustion environment to determine the feasibility of the corrosive/thermal barrier coating system and its effects on the flexural behavior of SiC/ SiC 5-harness satin weave composites. The experimental investigation consists of studying the load- displacement behavior of virgin to thermally soaked to coated materials, and understanding the failure mechanisms of SiC/ SiC composites during four-point bend testing. The specimens experienced both high temperature gradients and hygrothermal soaking. The load-displacement data from the laser four-point flexural test demonstrates that the coating ratio 1.5:1 combination outperforms the 0.6:1 coating ratio in the mechanical behavior of the composite specimens. The scanning electron microscope micrographs demonstrate that hygrothermal soaking degrade the material, causing a reduction in mechanical strength.