Microstructure and Antiwear Property of Laser Cladding Ni-Co Duplex Coating on Copper.

Ni-Co duplex coatings were cladded onto Cu to improve the antiwear properties of Cu products. Prior to laser cladding, n-Al₂O₃/Ni layers were introduced as interlayers between laser cladding coatings and Cu substrates to improve the laser absorptivity of these substrates and ensure defect-free laser cladding coatings. The structure and morphology of the coatings were characterized by scanning electron microscopy and optical microscopy, and the phases of the coatings were analyzed by X-ray diffraction. Their hardness was measured using a microhardness tester. Experimental results showed that defect-free composite coatings were obtained and that the coatings were metallurgically bonded to the substrates. The surface of the Ni-Co duplex coatings comprised a Co-based solid solution, Cr₇C₃, (Fe,Ni) ₂₃ C₆, and other strengthening phases. The microhardness and wear resistance of the duplex coatings were significantly improved compared with the Cu substrates. The average microhardness of the cladded coatings was 845.6 HV, which was approximately 8.2 times greater than that of the Cu substrates (102.6 HV). The volume loss of the Cu substrates was approximately 7.5 times greater than that of the Ni-Co duplex coatings after 60 min of sliding wear testing. The high hardness of and lack of defects in the Ni-Co duplex coatings reduced the plastic deformation and adhesive wear of the Cu substrates, resulting in improved wear properties.