Plasma-sprayed thermal barrier coatings are highly insulating due to intersplat pores. High-temperature exposure, however, leads to pore healing and a loss of thermal insulating capability. Previous sintering models based on the healing of iso-thick pores cannot explain the ultrafast sintering kinetics observed during the initial sintering stage. To better understand the sintering process and the kinetics of pore healing, a study was conducted on the changes that occur at the interfaces between lamellae at high temperatures. It was found that splat surfaces develop multiscale convexes, forming bridges between adjacent splats that significantly accelerate pore healing. This model explains the fast sintering kinetics of the initial sintering stage and presents new opportunities to further tailor the sintering kinetics of YSZ coatings and thereby improve TBC performance.

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