Novel HfSiO ₄ Coat: High‐Temperature Bond Coat for Thermal/Environmental Barrier Coatings

ABSTRACT Traditional Si bond coats limit the increase of thrust‐to‐weight ratio in aero‐engines due to insufficient temperature resistance; hence, it is extremely urgent to develop new bond coats capable of withstanding higher temperatures (>1350°C). Herein, we select HfSiO 4 as a novel bond coat material and investigate the effects of atmospheric plasma spraying (APS) parameters and annealing conditions on the coatings. The as‐sprayed HfSiO 4 coatings are relatively dense, with a porosity <2%. After annealing, the coatings exhibit excellent thermal stability, showing no phase transition from room temperature to 1450°C. They also possess a matched thermal expansion coefficient (5.1–5.5 × 10 −6 °C −1 ) with the SiC substrate and low thermal conductivity (3.16–2.19 W/(m·K)), along with high hardness (11.79 ± 1.22 GPa), and high modulus (166 ± 26 GPa). Research results show that the prepared HfSiO 4 coatings are promising bond coats for thermal/environmental barrier coatings (T/EBCs) due to their excellent overall properties.