Perparation And Properties Of TiB₂-MoB₂-SiC/Cu Composites By Laser Cladding

Copper and its alloy were widely used in aerospace,industrial and other fields due to their excellent thermal,mechanical properties and high electrical conductivity.However,due to its poor strength and wear resistance,its service life received a severe test in harsh environment,and laser cladding as an excellent surface modification technology can significantly improve its surface properties.SiC-MoB₂-TiB₂/Cu composite coating was prepared in pure Cu matrix by in-situ laser cladding,in which electrolysis Cu powder as matrix powder,TiC powder,MoSi₂ powder and Ni-coated B₄C powder as cladding powders.The mechanical and physical properties of the coatings were studied,and the parameters of the laser process and the content of the reinforced phase were determined.Then the high-speed friction and abrasion with/without current tests were carried out.The microstructure and properties of the coatings were investigated by metallographic?OM?,X-ray diffraction?XRD?,scanning electron microscopy?SEM?and transmission electron microscopy?TEM?.The results showed that the laser energy density was 73.33kJ/cm2?P=2200W,v=1mm/s?,which could be obtained by analyzing the surface morphology,interface bonding,conductivity and tensile strength of the cladding layer under different laser parameters.The optimized content of laser cladding powder was changed,and the mechanical and physical properties were analyzed.Changed the content of the cladding powders under the optimization of the laser process,it was determined that optimization content of the enhanced phase was 20% by analyzing the mechanical and physical properties.tested The performance of the composite coatings under the optimal conditions,the dilution rate was 10.3%,the conductivity was 9.47%IACS,the microhardness was above 1680 MPa,and the tensile strength was above 380 MPa.The microstructure and phase analysis of the cladding layer with optimized laser parameters and phase contents were studied by XRD and TEM.The results showed that the strengthening phase existed in dendrite,and the phase contents were decreased slightly from the surface to the matrix.The results showed that the main phases of the formation were TiB₂,MoB₂ and SiC,and also found that there were C,CuB₂8,Cu₂Ti phases.Interface analysis showed that the interface was metallurgical interface and the components were interdiffused by high angle annular dark field.the initial friction coefficient of the composite coating increased rapidly to about 0.292 and then decreased rapidly and maintained steady and slowly declined.The friction coefficient increased as a whole with current,and then increases rapidly to about 0.340 after 80s and slowly declined.The higher contents of TiB₂,MoB₂ and SiC in the composite coating,the better the wear resistance of the coating,and the content of the composite coating was 20%;When the sliding speed was 80m/s,the composite coating showed severe adhesive wear,and the wear rate was 0.92mg/km.When the loading was more than 60N,the wear rate increasesd slowly,which was 8.92mg/km,and increasesd to 10.37mg/km at 80N.After all of the test current loading,the wear surface had different degrees of electrical ablation and oxidation,and the wear rate increasesd.