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为了改善钛合金的硬度和耐磨性能,利用5 k W YLS-5000光纤激光器,在TC4合金表面分别激光熔覆纯Ti粉、Ti-15%(Mo+Si)和Ti-30%(Mo+Si)混合粉末(质量分数,Mo与Si原子比为1∶2),通过正交实验选择合适的功率和扫描速度等工艺参数,得到3种不同的涂层,利用金相显微镜(OM)、扫描电镜(SEM)对熔覆层的微观组织进行观察和研究、X射线衍射仪(XRD)研究熔覆层相组成,用显微硬度仪测得3种熔覆层的硬度。结果发现,功率为3 k W扫描速度10 mm·s-1得到熔合较好,缺陷较少的熔覆层。熔覆纯钛粉涂层组织为细小针状马氏体α’相,熔覆Ti-15%(Mo+Si)涂层在界面处共析出白色条状Ti Si2,熔覆Ti-30%(Mo+Si)涂层上部出现了镶嵌在涂层中的分块状Mo5Si3,MoSi2硬质相,而且白色晶间析出物增多,XRD结果显示β相增多。3种涂层熔覆区硬度有很大的区别,熔覆纯钛粉涂层平均硬度为HV0.2500左右,熔覆Ti-30%(Mo+Si)涂层最高硬度达到了HV0.21120,是基体的3.4倍左右。分析比较了3种涂层组织差异的原因,Mo,Si元素添加对钛合金组织的影响,结合热力学分析,探讨混合粉末形成Mo Si2的反应机制。
In order to improve the hardness and wear resistance of titanium alloy, pure Ti powder, Ti-15% (Mo + Si) and Ti-30% (Mo + Si) powder (mass fraction, atomic ratio of Mo and Si is 1: 2). Three kinds of coatings were obtained by orthogonal experiments such as power and scanning speed. The microstructure of the cladding layer was observed by scanning electron microscopy (SEM). The phase composition of the cladding layer was investigated by X-ray diffraction (XRD). The hardness of the three cladding layers was measured by microhardness tester. The results showed that the power of 3 k W scanning speed of 10 mm · s-1 get good fusion, less defects cladding. The microstructure of the pure titanium coating was fine acicular martensite α ’phase. The white Ti12 strip was co-precipitated at the interface of the cladding Ti-15% (Mo + Si) coating, and the Ti-30% Mo + Si) coatings appeared in the coating mosaic block Mo5Si3, MoSi2 hard phase, and white intergranular precipitation increased, XRD results show that the β phase increased. The hardness of the three kinds of coating has a great difference, the average hardness of the pure titanium coating is about HV0.2500, and the maximum hardness of the cladding Ti-30% (Mo + Si) coating reaches HV0.21120, 3.4 times the matrix. The reasons for the differences in the three coating compositions, the effect of Mo and Si addition on the microstructure of the titanium alloy were analyzed and compared. The reaction mechanism of the mixed powder to form Mo Si2 was discussed based on the thermodynamic analysis.