MICROSTRUCTURE INVESTIGATION ON GRADIENT POROUS THERMAL BARRIER COATING PREPARED BY EB-PVD

摘要

A new type of gradient thermal barrier coating was prepared by co-deposition of mixtures of Al_2O_3-ZrO_2 onto NiCoCrAlY bond coat by means of EB-PVD.·1. Microstructure of the coating gradually transferred from metallic bond coat to YSZ topcoat and composition distribution across the thickness of the coating changed continuously. In the two-phase Al_2O_3+ZrO_2 transition region, #alpha#-Al_2O_3 phase was dispersed in the matrix of ZrO_2 in the form of particle.·2. Due to the formation of gradient micro-porous structure in the gradient coating, micro-hardness distribution in the ceramic layer of the coating revealed an increase towards the outer YSZ topcoat, and with the rise of substrate temperature, the micro-hardness became smaller.