| Laser cladding metal-ceramic composite is an advanced surface modified technology, which can combine the high toughness of metal with the strength of ceramic and improve the material surface performance, such as wear resistance, corrosion resistance, and oxidation resistance and so on. The laser cladding of Co/SiC alloys and Co/SiC coating adding rare earth oxide on 45 steel matrix was prepared by high power continuous wave CO2 laser. Microstruction of the cladding coating is studied by means of X-ray diffraction, scanning electron microscope and electron probe micro-analyzer (EPMA). The microhardness of the coating is measured using DMH-2LS type knoop hardness tester. Characteristics of the layers are studied using an UMT-2 type friction wear tester.The results of laser cladding Co50/SiC composite coating show that:The quality of Co50 laser cladding layer is very good. There is no crack and porosity existed in the Co50 laser cladding coating. The phase composition of Co50 layer is y-Co solid solution,Cr23C6, Cr7C3 and Cr3C2. The Co50/SiC laser cladding layer mainly consists ofγ-Co solid solution, Cr23C6, Cr7C3, Fe3C and WB4. Single SiC phase is not found in the layer. The SiC in the power is completely dissolved during laser cladding process under this condition. One part of C and Si decomposed from SiC solublizes in y-Co solid solution, the other react with other elements in the melting pool at high temperature. The microstructure of Co50/5%SiC is composed of dendrite in the bottom and upper equiaxial crystal. The microstructure of Co50/10%SiC is composed by dentrite and white particles. Along with the increase of space from combining interface, white particles increase in the cladding coating. Adding 15% SiC to the Co50/SiC powder make the grain fine, the network increase and the particles increase. The mechanical properties analysis shows that:The micro-hardness of the Co50 cladding is significantly higher than that of 45 steel, and the micro-hardness of Co50/SiC is higher than Co50 layer. The wear resistance of Co50 coating is three times than 45 steel, and the wear resistance of composite coating with 5%,10%, and 15% SiC greatly improved.The results of laser cladding Co50/SiC composite coating with CeO2 addition show that: Compared with the coating with no rare earth oxide, the composite coating with CeO2 addition reduce the gain size, decrease the role and crack, enlarge the equiaxial crystal and shorten dentrite area. The wear resistance of composite costing is improved at little expense of a decrease in Micro-hardness. Compared to the addition of 4%,6% and 8% CeO2, 2% CeO2 is the best.In addition, compared with particle reinforced metal matrix composite, the ceramic reinforcements with high strength in the in-situ synthesis of composite is the thermodynamics steady phase, which nucleates and grows in the matrix. So, the enforcement is more compatible with the matrix. Laser cladding of Co50 and Co50/Ti+B composite layers on TC4 alloy was carried out by laser cladding. The coating with Ti and B compared to Co50 coating has more TiC and TiB. The TiC and TiB has beneficial effect on the wear resistance. The wear resistance of Co50 coating is significantly higher than the substrate. The wear resistance of cladding coating with Ti and B addition is higher than Co50 coating. |
