采用激光熔覆沉积工艺,在传统TC4合金表面以单道多层的方式熔覆Ti40 (Ti-25V-15Cr-0.2Si)阻燃钛合金。重点研究了不同激光功率下熔覆层形貌特征、成分及显微硬度的演变规律,并建立了不同激光功率下的稀释率及熔覆层过渡区成分的理论预测方法。实验及分析结果表明:TC4基体区与Ti40激光熔覆区交界处存在成分及显微硬度过渡区域,特别是在过渡初期的300~350 μm范围内,4种激光功率下均出现成分及显微硬度的显著变化;当激光功率为1800 W时,Al、V、Cr元素含量及显微硬度过渡得最快;随着激光功率的增大,过渡区尺寸逐渐减小。基于过渡区成分分析及Mo当量计算发现,由热影响区向熔覆区域过渡时,显微组织直接发生α+β→β转变,导致熔覆界面处显微硬度显著降低。

Laser cladding deposition is used to fabricate the Ti40 (Ti-25V-15Cr-0.2Si) flame-retardant layers on the surfaces of traditional TC4 alloys. Further, the composition, microstructure, and microhardness distribution of the cladding layer are subsequently investigated. Subsequently, theoretical methods are established for predicting the dilution rate and composition of transition zone of cladding layer under different laser powers. The experimental and analysis results show that there is a transition zone with respect to the composition and microhardness at the interface between the TC4 matrix and the Ti40 laser cladding zone; in 300-350 μm of the transition zone, significant composition and microhardness changes are observed under four laser powers. Among the four laser powers, the laser power of 1800 W results in the most substantial changes with respect to the microhardness and element contents of Al, V, and Cr. With increasing laser power, the size of the transition zone gradually decreases. Furthermore, the results of composition analysis of transition zone and Mo equivalent calculation show that the direct transformation of α+β→β causes the sudden change of microhardness at the cladding interface when the heat affected zone transfers to the cladding area.