FeCl₃∙6H₂O was used as raw material to produce Fe₃O₄, using the solvothermal method with ethylene glycol as the solvent. Fe₃O₄, with different particle sizes, was obtained via mechanical ball-milling by controlling the milling time. Effect of the milling time on the structure, morphology, and electromagnetic parameters of Fe₃O₄ were studied, and the absorption properties and mechanism of Fe₃O₄, for different milling times were analyzed. The results showed that the integrity of the original small spherical structure decreased as the ball milling time increased. Fe₃O₄ showed excellent microwave absorptions as the milling time reached 2 h, the reflection loss reached the maximum of −21.19 dB at 4.64 GHz as the thickness was 6.55 mm.

The incorporation of a homogeneously distributed nanocrystalline phase in Fe-based amorphous coatings is widely acknowledged to enhance wear resistance across various applications. In this study, FeCrMoWBRE amorphous/nanocrystalline composite coatings were fabricated on 45# steel substrates using high-velocity arc spraying (HVAS). The coatings were produced under varying spraying voltages, currents, and distances, following the Taguchi experimental design methodology. The microstructure, mechanical properties, and wear resistance of the coatings were systematically analyzed, with a particular focus on the relationship between nanocrystalline/amorphous phase content and key performance metrics, including microhardness, adhesive strength, and wear rate. A positive correlation was observed between the nanocrystalline phase content and both mechanical properties and wear resistance. The coating with optimized nanocrystalline phase content of 21.4% exhibits the lowest wear rate of 1.39 × 10⁻⁷ mm³·N⁻¹·m⁻¹ under a 100 N load and oil lubrication. These findings underscore the critical role of controlling the nanocrystalline phase content in Fe-based amorphous/nanocrystalline composite coatings to maximize wear resistance under oil-lubricated conditions.