Abstract
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)23C6, 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.
Highlights
Cu-based alloys are well known to be highly useful in the metallurgical and electrical industries because of their high thermal and electrical conductivities
Surface coatings provide a possible solution to the wear resistance problem of Cu materials and potentially extend the service life of
Laser surface cladding (LSC) technology has been used for continuous casting molds, obtaining large-surface-area, defect-free coatings on the surface of Cu substrates is difficult because of a high laser reflectivity of Cu materials and a low wettability of these materials on many metals
Summary
Cu-based alloys are well known to be highly useful in the metallurgical and electrical industries because of their high thermal and electrical conductivities. Low slide wear resistance of Cu materials under severe conditions, especially under high temperatures, limits their application as crystallizers in continuous casting. Researchers’ interest in coating technologies involving electrodeposition, plasma spraying, and infiltration has been increasing Such methods can improve the wear resistance of Cu materials to a certain degree, their applications are limited because they rely on mechanical bonding between a coating and substrate. Yan et al laser cladded Co-based alloy/TiC/CaF2 self-lubricating composite coatings onto Cu alloys; resulting cladded alloys exhibited good friction-reducing and antiwear abilities at temperatures as high as 400 ̋ C [9]. LSC technology has been used for continuous casting molds, obtaining large-surface-area, defect-free coatings on the surface of Cu substrates is difficult because of a high laser reflectivity of Cu materials and a low wettability of these materials on many metals. The Ni–Co duplex coatings exhibit good mechanical strength and surface hardness, excellent chemical durability, and high antiwear performance in high-temperature, corrosive environments
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