Microstructural and Tribological Behavior of Thermal Spray CrMnFeCoNi High Entropy Alloy Coatings

High entropy alloys (HEAs) are characterized as alloys containing five or more principal elements in equal or close to equal atomic percentage. HEAs as bulk materials and coatings are considered a potential candidate for high-temperature applications owing to their superior combination of mechanical and thermal properties. In the present study, the CrMnFeCoNi HEA coatings were developed using high-velocity oxygen fuel (HVOF) and annealed at 800 °C for 2 h. The microstructure and wear behavior of the as sprayed and annealed HEA coatings were systematically evaluated on rough and polished surfaces. The wear behavior of these HEA coatings against an alumina (Al2O3) ball was tested at room temperature. Ex situ characterization was performed using XRD and Raman spectroscopy for phase analysis, SEM-EDS for cross-section microscopy and phase compositions of the HEA coatings. Both the as sprayed and annealed coatings comprised the FCC solid solution phase with the formation of oxides. The tribological results showed equivalent behavior of as sprayed and heat-treated coatings on the polished surfaces. Rough surfaces, on the other hand, revealed significantly higher wear rates compared to the polished surfaces due to third body abrasion during sliding. A strong emphasis was placed on correlating the interfacial processes to the tribological behavior.