Refractory multicomponent boron-carbide high entropy oxidation-protective coating for carbon-carbon composites

Abstract A novel refractory multicomponent boron-carbide coating of 300 nm thickness, HfMoTaTi-BC, was deposited on carbon‑carbon composites (CCC). The coating showed a face-centred cubic (FCC) structure of lattice parameter of 0.4429 nm with an average crystallite size of 5 nm. The FCC coating transformed from single-phase solid solution into multiple ceramic carbides and boride phases at 900 °C during long-term thermal stability test. The exposure of HEC coated CCC to the flame (2000 °C) of liquefied petroleum gas (LPG) torch for 5 min revealed that the film had excellent resistance to oxidation and protected the CCC material under extreme aerothermal heating.