Preparation And Properties Of In-Situ ZrB₂-ZrC/Cu Composite Coating By Laser Cladding

Cu and its alloys were widely used in aerospace, aviation, automobile industries and electrical contact components due to their high electrical conductivity, thermal conductivity and excellent corrosion resistance. However, due to their poor resistance to sliding wear and low tensile strength, their potential applications and service life in the various industries and electrical contact components were limited. Compared with the traditional surface engineering, such as thermal spraying, surface overlaying and gas tungsten arc welding, laser cladding exhibited a high efficiency, good interface bonding and thick coating. Therefore, laser cladding had drawn much attention in the surface engineering field.In this paper, Cu, Cu-54 Zr and nickel-coated B4 C powder were uniformly mixed by a planetary ball mill machine. The ZrB2-ZrC/Cu ceramic composited coating was in-situ synthesized by laser cladding, and properties under different preparation process were tested. With the various of ZrB2-ZrC reinforcement content, the physical and mechanical properties of the coating were tested and got the best added amount of reinforcement. The interfacial reaction and phase formation between matrix and reinforcement phase, tensile properties and tribological properties of ZrB2-Zr C/Cu ceramic composited coating were observed and analyzed by X-ray diffraction(XRD), transmission electron microscopy(TEM), scanning electron microscopy(SEM), optimal microscope(OM), tensile testing machine and high-speed friction were testing platform.The experimental results demonstrated that the optimum technique parameter of ZrB2-ZrC/Cu composited coating were the power 2800 W, the scanning speed 3mm/s, the beam diameter 3mm and the overlap rate 50%, respectively. The properties of the composited coating were tensile strength 340 MPa and the conductivity 43 %IACS.XRD and TEM analyzed the interface and component existing form between phase and substrate. The results showed that ZrB2-ZrC ceramic particles were synthesized by the reaction of B4 C and Cu-Zr powder during laser cladding process. The reinforcement particles were uniformly distributed in the coating. The ZrB2 presented a wide range of morphologies, including rectangle shape, needles and lamella, while the ZrC presented irregular cubic shape. High resolution electron microscopy presented ZrB2 and ZrC forming clearly interface with Cu substrates.The tribological behavior of the ZrB2-ZrC/Cu composite coatings were tested. The effect of ZrB2-ZrC content on the tribological properties of the laser cladding Cu based cermet composite coatings were investigated. The experimental results demonstrated that with the increase of sliding speed, the original slight abrasion worn mechanism of the coating was changed into delamination wear. With the reinforcement content for further increased, the wear resistance of the coating was enhanced and the adhesive wear mechanism changed into abrasire wear mechanism.