Cold sprayed Fe–Cr–Co–Ni–Mo–Ta multicomponent alloy coatings: Microstructural evolution and deformation behavior

Fe–Cr–Co–Ni–Mo–Ta alloy powders were deposited onto mild steel substrates using the cold spray process, and the resulting microstructural evolution and hardness of the coating were systematically investigated. The ultrasonic atomized powders were predominantly spherical, with a narrow particle size distribution and a median diameter (D50) of approximately 35 μm. Cross-sectional analysis of individual particles revealed heterogeneous plastic deformation characterized by localized jetting at particle edges, and subgrain structures resulting from severe plastic deformation and adiabatic shear localization. Electron backscatter diffraction (EBSD) analysis showed pronounced lattice rotation, high local misorientation, and low angle grain boundaries (LAGBs) as the dominant deformation features, accompanied by localized deformation twinning. Kernel Average Misorientation (KAM) analysis confirmed significant strain localization near particle boundaries. Molecular dynamics (MD) simulations indicated that the moderate stacking fault energy (SFE) of the Fe–Cr–Co–Ni matrix promotes dislocation mediated deformation with localized twinning under high strain rate conditions. Nanoindentation revealed a progressive increase in hardness from 5.3 GPa for the feedstock powder to 6.1 GPa within particle interiors and 7.8 GPa near particle boundaries. A quantitative strengthening analysis demonstrated that the hardness enhancement is primarily governed by the combined effects of dislocation strengthening induced by severe plastic deformation and grain/twin boundary strengthening associated with microstructural refinement. These findings demonstrate that cold spray processing produces Fe-based multicomponent alloy coatings with refined microstructures and superior hardness, highlighting their potential for protective coating applications.