Effect of Mo addition on structures and properties of FeCoNiCrMn high entropy alloy film by direct current magnetron sputtering

FeCoNiCrMnMox high-entropy alloy (HEA) films were prepared by direct current (DC) magnetron co-sputtering. The influence of the Mo content on the microstructures and mechanical properties of the HEA films were systematically studied by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), Vickers hardness test and tribological test. The addition of Mo results in the formation of a denser film with refined grain size, and promotes the transformation from a face-centered cubic (FCC) phase to a mixture of FCC and body-centered cubic (BCC) phases. The hardness of the films increases from 8.5 GPa (x = 0) to 12 GPa (x = 1) and the friction coefficient decreases from 0.5 (x = 0) to 0.3 (x = 1), which greatly enhance the damage tolerance of the film. The improved mechanical and tribological properties of the HEA films are attributed to the formation of the hard BCC phase and grain refinement at high contents of Mo. The FeCoNiCrMnMox HEA films are suitable candidates for structural application as protective coatings.