Investigation of elevated temperature microstructural stability and tribological behavior of MoxNbTiZr refractory high-entropy alloy coatings optimized by Mo-doping

Refractory high-entropy alloys (RHEAs) possess substantial potential for applications in high-temperature environments. In this work, the structural and high-temperature properties of MoxNbTiZr RHEA coatings are optimized by Mo-doping. The results show that Mo-doping promotes the HCP phase precipitation and proliferation of nanotwins, strengthening the microhardness but weakening the fracture toughness of the coatings. Mo-doping raises the phase transition onset temperature and end temperature by reducing the bulk diffusion rate of MoxNbTiZr RHEAs. The BCC phase of Mo1.0NbTiZr HEA coating can be stabilized to at least 1300 ℃. Mo-doping in a particular range is favourable to accelerate the sintering and curing rate of the tribo-layer. The MoxNbTiZr RHEA coatings demonstrate outstanding high-temperature tribological performance before Mo content exceeds 0.6at.%.