Influence of HVOF spraying parameters on microstructure and mechanical properties of FeCrMnCoNi high-entropy coatings (HECs)

The study aimed to investigate the impact of high velocity oxy-fuel (HVOF) spraying parameters on the inflight particle temperature, velocity, and microstructure of FeCrMnCoNi high-entropy coatings (HECs). The sprayed coatings exhibited a typical lamellar structure with a single solid solution FCC phase and minor oxides. Ex-situ characterization of the coatings was conducted using X-ray diffraction, Raman spectroscopy, and high-resolution scanning electron microscope (HR-SEM) to analyze the phase composition, microstructure, and surface morphology. The findings revealed that fuel-rich flames with a higher feed rate resulted in coatings with low porosity and oxidation as well as high deposition efficiency due to the high velocity and low particle temperatures. Additionally, the transverse scratch tests were conducted to determine the cohesive/adhesive nature of the coatings, and the results demonstrated that the cohesive strength between the splats was influenced by the porosity and area fraction of the oxides. Coatings deposited with oxygen-rich conditions showed maximum hardness, but low cohesive strength compared to coatings sprayed using fuel-rich conditions due to higher oxides formation during spraying. The microstructural changes, phase compositions, and microhardness of the coatings were correlated with the scratch resistance of the HECs developed using three distinct spraying conditions. These results suggest that FeCrMnCoNi HECs hold significant potential for surface protection in various industrial and aerospace applications. Moreover, the findings point toward new material design strategies to attain desired microstructure with enhanced mechanical properties. Graphical abstract