Refractory High-Entropy Alloys (RHEAs) have rapidly emerged as one of the most promising classes of ultra-high-temperature materials for liquid rocket engine (LRE) combustion chambers and throat liners, where structural components are subjected to some of the most aggressive thermochemical environments in aerospace engineering. LRE combustion zones routinely exceed 3000 K, expose walls to heat fluxes of 15–25 MW/m², and generate extreme thermal gradients often surpassing several hundred kelvin per millimetre. These conditions accelerate creep deformation, promote oxidation induced embrittlement, and destabilise strengthening phases in conventional Ni-based superalloys, ultimately limiting their service life and reusability (Miracle & Senkov,2017). As propulsion systems move toward higher chamber pressures and more demanding duty cycles, material systems capable of maintaining structural stability beyond the limits of current superalloys are required. RHEAs—particularly multi-principal-element systems such as Ti–Zr–Nb–Ta–Mo—offer a fundamentally different pathway for achieving the thermomechanical performance required for next-generation reusable engines. Their exceptionally high melting points (>2000°C), combined with severe lattice distortion and sluggish atomic diffusion, suppress dislocation mobility, delay diffusion-controlled degradation, and enhance creep resistance under sustained thermal loading. The entropy-stabilised BCC solid-solution phases commonly exhibited in t