脉冲激光熔覆Inconel 718涂层热行为数值模拟及其对显微组织的影响

目的 揭示脉冲激光作用下Inconel 718合金涂层凝固传热行为的演化机制，改善涂层中Nb、Mo元素偏析现象，提升Inconel 718合金熔覆涂层的力学性能，为优化Inconel 718熔覆涂层质量提供理论依据。方法 综合考虑物性参数随温度、脉冲激光热源、粉末传输形式，以及凝固过程中相变潜热对涂层凝固热行为的影响，构建脉冲激光熔覆传热模型。基于数值模拟技术和激光熔覆试验，利用VHX-2000电子显微镜对涂层显微组织形态进行分析验证，采用日立SU8010场发式扫描电镜观察分析显微组织和元素偏析情况，并使用显微硬度计测试涂层的硬度值。结果 由数值模拟分析结果可知，脉冲激光涂层的冷却速度、温度梯度、凝固速度均大于连续激光涂层，其枝晶生长细密且No、Mo元素呈弥散分布，显微组织自底向顶以平面晶、胞状枝晶、柱状枝晶、等轴枝晶等形式存在，Laves相的体积分数降低至2.93%，在细晶强化和固溶强化作用下，熔覆涂层的平均显微硬度提升至307HV0.1。结论 脉冲激光涂层热行为数值模拟分析结果符合Inconel 718涂层组织形态快速凝固变化的规律，数值模型可靠。脉冲激光形成的高冷却速度和高温度梯度，能在一定程度上抑制Inconel 718合金涂层中Nb、Mo元素的偏析，离散并细化γ枝晶组织，降低Laves相的体积分数，显微组织在细晶强化和固溶强化双重作用下，提升涂层的力学性能。

Numerical Simulation of Thermal Behavior of Inconel 718 Coating Prepared by Pulsed Laser Cladding and Its Effect on Microstructure

As a new green and environment-friendly material preparation technology, laser cladding technology expands the use of Inconel 718 alloy materials, but the non-equilibrium solidification process of cladding pool is often accompanied by the segregation of elements such as Nb and Mo, finally forming Laves phase. At the same time, the high-heat laser input is easy to coarsen the dendritic structure and reduce the mechanical properties of the coating. For this reason, the work aims to investigate the evolution mechanism of solidification heat transfer behavior of Inconel 718 alloy coating under pulsed laser to explore the effects of pulsed laser on element segregation, microstructure and mechanical properties of the coating, so as to provide a theoretical basis for optimizing the quality of Inconel 718 cladding coating.