Researches Of ZrB₂/Cu Multicomponent Alloys Coatings Prepared By Laser Cladding

Copper and copper alloy has many excellent properties such as high thermal conductivity and electric conductivity, excellent ductility and toughness. In this paper, a kind of ceramic reinforced metal matrix composite coating on the pure copper matrix was fabricated by laser cladding technology, in which copper alloy powders were the cladding material and ZrB₂ ceramic particles acted as the reinforcing phases. The microstructure of the laser cladding coatings, the morphology and distribution of ZrB₂ particles, and the effect of different ZrB₂ content on performance were studied by means of X-ray diffraction analyzer（XRD）, scanning electron microscopy（SEM）, and transmission electron microscopy（TEM）. In addition, the tribological properties of Cu-ZrB₂ composite materials were tested on high-speed friction and wear testing platform.The experiment results showed that the optimum power density was 31.11 k J/cm2, the content of ZrB₂ was 6wt.% considering all factors such as surface appearance, micro-hardness, conductivity, tensile strength, the tensile strength was 360 MPa, conductivity was 26%IACS.The researches were focused on the microstructure of ZrB₂/Cu composite coating, It was also analyzed the phases composition of other elements. The results of XRD showed that the main phases in the coating were Cu and ZrB₂. The ZrB₂ in cladding layer was distributed gradient in the longitudinal, namely the surface content was higher than the bottom content. The form of ZrB₂ was strips in cladding layer surface, but a fine needle at the bottom. The study found that the cladding layer generated the CrCo, FeSi, Ni3 Si phases, and the spherical FeNi phase was precipitated at the grain boundary. The interface between Zr B₂, CrCo, Fe Si, Ni3 Si and Cu was analyzed by TEM. It found that those phases had good interfacial bonding with the matrix.When the sliding speed was 37.5 m/s, the friction coefficient and wear rate continued to decrease with the increasing of content of ZrB₂. The wear mechanism was adhesive wear at a lower ZrB₂ content, but it changed to abrasive wear when the content of Zr B₂ was higher. Under the condition of current-carrying friction and wear, the friction coefficient and wear rate at different speeds were greater than that of not loaded current condition. When the speed exceeded 50 m/s, the wear rate of loaded current increased rapidly. At lower speed, the wear mechanism were abrasive wear in both conditions, with the increasing sliding speed, it changed to the adhesive wear, and became more serious under the loaded current. In the process of friction and wear, the friction coefficients were initially higher, then showed a stable trend and decreased slowly. The friction coefficient stabilized rapidly than the other ones when loaded current.