Constrained Sintering on Thermally Sprayed Thermal Barrier Coatings by Mismatch of CTE Between Substrate and Yttria Stabilized Zirconia

As key performance of TBCs, stiffness and thermal conductivity are inevitably deteriorated by healing up of lamellar cracks during high temperature exposure. However, most sintering publications were based on free-standing coatings, which ignored stress caused by mismatch of CTE between substrate and topcoat. In this paper, single splat of YSZ has been sprayed on YSZ substrate and Ni-based alloy and three types of YSZ coatings have been prepared. Mechanical property and thermal conductivity tests were conducted for them. Results showed that, the mismatch of CTE caused about 1/5 widening on intra-splat cracks. Compared with free-standing coating, the coating sprayed on YSZ demonstrated some retard with same increasing trend on performance. However, for coating sprayed on Ni-based alloy, a significant decrease in mechanical properties occurred after the first thermal cycle except for sintering stiffening during long duration thermal exposure. SEM of cross-section showed some medium scale cracks appeared in out-plane direction.