Oxidation influences on the microstructure and mechanical properties of W-Nb-Mo-Ta-V-O refractory high-entropy alloy films

Refractory high-entropy alloys (RHEAs) have great potential for aerospace engineering applications as high-temperature load-bearing structures or thermal protection systems. However, there is still a lack of in-depth study on their oxidation mechanism and structural evolution, which would considerably have a negative impact on their mechanical properties. In this study, nano-structured RHEA W-Nb-Mo-Ta-V-O films were developed by magnetron sputtering. Subsequently, oxidation experiments were carried out under different temperatures to study their oxidation behavior, and the influence on microstructure and mechanical properties were further investigated. The results showed that the as-deposited film had a very fine nanocrystalline structure with a typical body-centred cubic (BCC) solid solution phase. There was no significant change in the crystallite size when the film was oxidized below 400 degrees C for 2 hours, and the RHEA film exhibited a specific structure and phase stability. As the oxidation temperature increased to 500 degrees C, the crystallite size increased from 5.588 nm to 6.549 nm. Most specifically, the RHEA film was completely oxidized when the temperature reached 600 degrees C. The nanohardness and elastic modulus of the deposited films were 8.58 +/- 0.85 GPa and 148.02 +/- 7.48 GPa, respectively, and decreased rapidly to 4.58 +/- 0.32 GPa and 96.6 +/- 4.47 GPa after oxidation at 500 celcius for 2 hours. However, the films exhibited stable mechanical properties under oxidation conditions up to 400 celcius, which would provide a new paradigm for future high-temperature applications.

Automated summary

Nano-structured refractory high-entropy alloy films were prepared and their oxidation behavior and effects on microstructure and mechanical properties were investigated. The films exhibited stable structure and mechanical properties under oxidation conditions up to 400 degrees Celsius.