Fabrication of thermal barrier coatings onto polyimide matrix composites via air plasma spray process

Thermal barrier coatings were fabricated on polyimide matrix composites via air plasma spray process. The phase structures and microstructural evolution of the coatings before and after testing were characterized by powder X-ray diffraction and scanning electron microscopy. During thermal shock test at 400 degrees C, thermal shock lifetime of the coating systems increased with the decrease of thickness of Al layer as well as the increase in that of YSZ layer. The coating system consisted of 30 mu m Al bond layer and 130 mu m YSZ top layer exhibited the best thermal shock resistance. Meanwhile, owing to the protection of the coating system, the weight loss of the sample decreased from 7.05% to 1.90%, while the corresponding mass ablation rate reduced from 0.48 mg s(-1) to 0.21 mg s(-1). Failure mechanism of the coatings was mainly ascribable to the residual stress during deposition, oxidation of substrate and thermal stress induced by mismatch in thermal expansion. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.