Ti-7.5Nb-4Mo-2Sn Alloy Laser Surface Modification And Wear-resisting Performance Study

New β Ti-7.5Nb-4Mo-2Sn alloy is important potential to find use as a implantmaterial due to their good biocompatibility, excellent corrosion resistance, low elasticmodulus and excellent super elastic energy. Aiming at improving wear resistance, in thisthesis, the surface of the Ti-7.5Nb-4Mo-2Sn alloy was modified by using the lasersurface alloying technology with Si/C, and clad with a Fe-base alloy cladding layer. Themicrostructure and wear resistance of these layers were studied. The main conclusionsare as follows,1. A Si/C alloying coating was successfully prepared on the surface of the Ti alloyby using the laser surface alloying technology, and the parameters of the laserprocessing were optimized. It is found that, under the conditions of the laser power of1200w, the scanning rate of6mm/s and the beam diameter of5mm, a defect-free coatingcontaining multi-phases can be obtained.2. The alloying coating consists of two layers. The microstructure of the top layermainly contains fine TiC particles and equiaxed Ti5Si3C1-xphase, while, in the layerclose to the substrate, dendritic TiC phase and eutectic phases of Ti3SiC2+β-Ti wereformed. The hardness of the top layer is up to1262HV0.2，which is much higher thanthat of the Ti-7.5Nb-4Mo-2Sn substrate (about225HV0.2). The friction coefficient of thecoating is much lower than that of the substrate. The coating wear volume loss is48.5%of the matrix alloy, The coating exhibits good wear-resistance in comparison withTi-7.5Nb-4Mo-2Sn substrate.3. A Fe base alloy cladding layer was prepared on the surface of theTi-7.5Nb-4Mo-2Sn alloy by using the laser cladding method, and the parameters of thelaser processing were optimized by using an orthogonal experiment. Microstructurecharacterizations of the cladding layer reveal that many interstitial phases or compounds,such as MX、MX2、M2X、M7C3、Fe3C、Cr23C6are formed in the cladding layer, andsurface of the layer is smooth, dense, and defect-free, indicating a perfect metallurgicalbonding between the cladding and the substrate.4．The micro-hardness and wear resistance property were evaluated. It is found thatthe hardness of Fe-base alloy cladding layer decreases gradually from the top surface tothe substrate, and a hardness gradient is formed in the transition layer. The hardness of the top layer is up to900HV0.2, which is four times as high as the substrate (about225HV0.2). The scan rate and power of laser have a significant influence on the wearresistance of the cladding layer, in which. the laser power shows stronger influence thanthe scanning speed...