Microstructure and properties of the laser cladded in-situ ZrB2-ZrC/Cu composite coatings on copper substrate

The ZrB2-ZrC reinforced Cu matrix composite coating was prepared on a copper substrate by laser cladding and a self-propagating high-temperature synthesis (SHS) reaction. The zirconium ceramics were in-situ synthesized according to the designed SHS reaction within the coatings. The macromorphology, microstructure, phase composition, the interface of the zirconium ceramic phase/metal matrix, microhardness and wear resistance of the composite coating were analyzed and discussed. The results indicated that the in-situ ZrB2 ceramic had a needle-like morphology, the preferred growth direction was [1¯1¯20], and the ZrB2 were coated with the Ni dendritic crystals. Ni formed an intermediate transition layer between the ceramic and the metal matrix. The submicron particle phases (ZrC) had a rectangular morphology in the copper matrix, and the side length was 500 nm. The hard ceramic fibers and particles were in-situ synthesized that were dispersed homogeneously in the metal matrix, which improved the mechanical properties of the coating. The mean value of the microhardness of the composite coatings was 410 HV0.2, which was nearly 6 times higher than that of the copper. The microhardness gradually decreased from the composite coating surface to the transition zone and then sharply dropped in the transition zone to the substrate. This trend agrees with the distribution of the ceramic reinforcements. The wear mechanism of the composite coating was a combination of abrasive wear and adhesive wear, and the wear volume loss was approximately 85% lower than that of the uncoated substrate.