Enhanced microstructure and properties of laser cladding CoCrNi medium-entropy alloy reinforced with W

To explore the regulatory mechanism of the W element on the microstructure properties of laser cladding CoCrNi medium-entropy alloy, CoCrNiWx (x = 0, 0.15, 0.3, 0.45, 0.6) medium-entropy alloy coatings with a gradient change in W content were fabricated on an AISI 1045 steel substrate. The microstructure of the coating shows that when x = 0, the coating presents a single FCC solid solution structure. When x > 0, μ phase intermetallic compounds precipitated in the coating, forming a biphase structure of FCC + μ phase. Microhardness testing revealed an upward trend in the microhardness of the CoCrNiWx coatings with increasing W content. Specifically, the W_0.6 coating has the highest average microhardness, attaining 351.59 HV_0.5, which is 1.84 times that of the W₀ coating. The wear resistance of the coatings is significantly improved with the addition of W. The average friction coefficient decreases from 0.774 to 0.598, and the wear volume reduces from 0.0673 to 0.0237 mm³. The wear mechanisms mainly include adhesive wear, abrasive wear, accompanied by oxidative wear. Electrochemical tests conducted in a 3.5 wt% NaCl solution demonstrated that W_0.6 has the highest self-corrosion potential (−0.460 V) and the lowest self-corrosion current (7.245 × 10⁻⁷ A/cm²), displaying optimal passivation behavior in the electrolyte. The research results provide a reference for the development of medium-entropy alloy coatings with excellent comprehensive properties.