(湘潭大学 材料科学与工程学院，湘潭 411105)
摘 要: 采用HL-5000型横流CO2激光器在氩气保护情况下对预置石墨和硅混合粉末的β型Ti-7.5Nb-4Mo-2Sn钛合金进行激光表面合金化处理，在合金表面原位生成碳、硅和钛的化合物改性层，并对其激光表面合金化改性层的显微组织和耐磨性能进行研究。结果表明，在激光功率1200 W、激光扫描速度6 mm/s、激光束斑直径5 mm条件下，得到表面平整、细密、无裂纹且与基体形成良好冶金结合的激光表面合金化改性层；改性层外表面主要由细小的TiC颗粒和等轴状Ti5Si3C1-x组成，而靠近基体的内表面层则由TiC枝晶相和共晶组织(Ti3SiC2+β-Ti)组成；改性层外表面硬度可达1262HV0.2，摩擦因数约为0.649，而基体的硬度约为225HV0.2，摩擦因数约为1.039；与基体合金相比，基体的表面合金化改性层表现出良好的耐磨性能。
关键字: 钛合金；激光表面合金化；显微组织；耐磨性能
（School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, China）
Abstract:A wear resistance in-situ modified coating was fabricated by 5.0 kW continuous wave CO2 laser alloying technique with silicon and graphite mixed powders on the substrate of a β-type Ti-7.5Nb-4Mo-2Sn under the protection atmosphere of Ar, and its microstructure and wear properties were investigated. The results show that, under the conditions of laser power of 1200 W, scanning rate of 6 mm/s and beam diameter of 5 mm, a defect-free coating with multi-phases was obtained. The coating consists of two layers. The microstructure of the top layer mainly contains fine TiC particles and equiaxed Ti5Si3C1-x phase, while, in the layer close to the substrate, dendritic TiC phase and eutectic phases of Ti3SiC2+β-Ti form. The hardness of the top layer is up to 1262HV0.2，which is much higher than that of the Ti-7.5Nb-4Mo-2Sn substrate (about 225HV0.2). The friction coefficient of the coating is about 0.649, which is much lower than that of the substrate (of about 1.039). The coating exhibits good wear-resisting performance in comparison with Ti-7.5Nb-4Mo-2Sn substrate.
Key words: titanium alloy; laser surface alloying; microstructure; wear resistance
