Optimizing the gradient pore distribution of YSZ coatings to achieve excellent thermal shock resistance

Abstract

Yttria-stabilized zirconia coatings, as thermal barrier coatings, require high bonding strength, low thermal conductivity and emissivity, and long thermal shock lifetime to provide superior long-term high-temperature protection for alloy substrates. Matched gradient pore YSZ coatings, featuring a low-porosity inner layer and a high-porosity outer layer, were designed by adjusting spray power during atmospheric plasma spraying and optimizing interlayer porosity gradients. The results showed that YSZ coatings with matched porosity gradients exhibited excellent bonding strength, moderate thermal conductivity, and infrared emissivity, alongside outstanding thermal shock resistance. The thermal shock lifetime exceeded 900 cycles at 1000°C, representing a nine-times improvement compared with conventional coatings. This enhancement in thermal shock resistance was attributed to the optimized porosity gradient design. The matched gradient effectively suppressed crack propagation during the early stages of thermal cycling promoted the formation of a dense Al₂O₃ layer at the interface and further inhibited the diffusion of Al into the coating.