High-Entropy Alloy Thin Films Deposited by Magnetron Sputtering for Extreme Environment Applications

Abstract

We report the synthesis and characterization of AlCrTiVNb high-entropy alloy (HEA) thin films deposited by reactive magnetron co-sputtering for applications in aerospace turbine environments exceeding 800°C. The as-deposited films exhibit a single-phase body-centered cubic (BCC) solid solution with nanocrystalline grain size of 12 ± 3 nm, hardness of 14.8 GPa, and elastic modulus of 285 GPa. Oxidation resistance testing at 900°C for 100 h in air produces a protective Al₂O₃-Cr₂O₃ duplex scale with parabolic rate constant kp = 1.2 × 10⁻¹³ g²·cm⁻⁴·s⁻¹, two orders of magnitude lower than equimolar NiCrAlY reference coatings. Thermal cycling between 25°C and 900°C (500 cycles) shows no spallation or cracking, attributed to the sluggish diffusion kinetics inherent to high-entropy compositions. These results establish HEA thin films as promising next-generation thermal barrier and oxidation-resistant coatings.