New coating processes to fabricate a low elastic modulus top coat for high performance thermal barrier coatings

Elastic moduli of YSZ top coats for thermal barrier coatings (TBCs) were measured, where the top coats were fabricated by the following different types of methods: a traditional atmospheric plasma spraying (APS) method; a hybrid plasma spraying (HYPS) method that has been originally developed by Yoshida group; and an electron-beam physical vapor deposition (EBPVD) process. The top coat material was ZrO ₂ stabilized by 8 mass%Y ₂O ₃. Through the work special attention was paid to investigate the effects of the processing methods, the process variables in APS and the long term thermal aging at high temperature. It was found that the advanced methods; HYPS and EB-PVD methods, could provide the top coat film with lower elastic moduli, that may have a beneficial effect to prevent the failures of TBCs induced by thermal stress. Some discussions were made for their low elastic moduli, based on the analysis of the microstructure of the top coats and the Eshelby's approach.