Thermophysical properties and cyclic lifetime of plasma sprayed SrAl ₁₂ O ₁₉ for thermal barrier coating applications

Abstract About 6‐8 wt% yttria‐stabilized zirconia (YSZ) is the industry standard material for thermal barrier coatings (TBC). However, it cannot meet the long‐term requirements for advanced engines due to the phase transformation and sintering issues above 1200°C. In this study, we have developed a magnetoplumbite‐type SrAl 12 O 19 coating fabricated by atmospheric plasma spray, which shows potential capability to be operated above 1200°C. SrAl 12 O 19 coating exhibits large concentrations of cracks and pores (~26% porosity) after 1000 hours heat treatment at 1300°C, while the total porosity of YSZ coatings progressively decreases from the initial value of ~18% to ~5%. Due to the contribution of porous microstructure, an ultralow thermal conductivity (~1.36 W m −1 K −1 ) can be maintained for SrAl 12 O 19 coating even after 1000 hours aging at 1300°C, which is far lower than that of the YSZ coating (~1.98 W m −1 K −1 ). In thermal cyclic fatigue test, the SrAl 12 O 19 /YSZ double‐ceramic‐layer coating undertakes a thermal cycling lifetime of ~512 cycles, which is not only much longer than its single‐layer counterpart (~163 cycles), but also superior to that of YSZ coating (~392 cycles). These preliminary results suggest that SrAl 12 O 19 might be a promising alternative TBC material to YSZ for applications above 1200°C.