Effect of Thermal Aging on Microstructure and Mechanical Properties of Plasma-Sprayed Samarium Zirconate Coatings

摘要

The rare-earth zirconates with the general formula of Ln₂Zr₂O₇ (Ln = rare-earth elements) having considerable low thermal conductivity and exhibiting good phase stability at high temperature have attracted particular interest in thermal barrier coating (TBC) applications. The Sm₂Zr₂O₇ coatings were deposited by plasma spraying, and the effect of thermal aging on their microstructure and mechanical properties was examined. The lamellar structure gradually disappeared with the temperature increasing for thermal aging. The evaluation by image analysis revealed that the amount of microcrack in coatings decreased with increasing aging temperature because of the increase in aspect ratio caused by microcrack healing, while no obvious change was observed in the spherical porosity. The as-sprayed Sm₂Zr₂O₇ coating exhibited low microhardness and elastic modulus, which increased with rise in aging temperature because of the microstructure reconfiguration; in addition, the ratio of microhardness to elastic modulus decreased with aging temperature increase, indicating a promotion in plastic property.