Grain growth limitation in the monolayer ZrB₂–SiC coating above 1700 °C

The cracking behavior along the interface (surface ZrO₂ layer and unoxidized ZrB₂–SiC layer) in the thermally sprayed ZrB₂–SiC coating above 1700 °C was investigated by cyclic ablation tests (2.4 MW/m²). Experiment and simulation results show that the rapid growth of surface ZrO₂ grains will greatly promote the interfacial micropores development until the formation of inter-laminar cracks. To address this issue, the laminated ZrB₂–SiC/ZrO₂ coating was prepared. The ZrO₂ interface layer effectively restrained surface ZrO₂ grain growth and improved the structural integrity by hindering the diffusion of liquid B₂O₃ and SiO₂ towards the surface. Compared with monolayer ZrB₂–SiC coating (−0.17 mg/s and −8.13 μm/s), the mass and linear variation rates of the laminated coating decreased by 35% and 60%, respectively.