目的 揭示QT600球墨铸铁激光熔覆动态演化过程的机理，为球墨铸铁熔覆过程中拓宽熔覆材料范围、优化工艺参数、改进熔覆质量提供理论依据。方法 同时考虑移动高斯热源、材料物性参数温变影响、熔池表面张力和浮力对熔融态金属流动的Marangoni效应等因素，建立球墨铸铁激光熔覆多场耦合三维数值模型。通过QT600球墨铸铁激光熔覆实验，利用Zeiss?SIGMA HD场发射SEM观察熔覆层的形貌及显微组织，采用QNESS?Q10M硬度仪测试熔覆层和基体显微硬度。结果 在光源中心形成了“椭球”状热影响区，沿激光扫描方向温度明显呈单峰分布，且周期性前移，流速在1 s时达到0.24 m/s，前半部熔池呈顺时针环流，后半部熔池呈逆时针环流，在活性元素影响下将导致熔池环流发生逆转。受温度梯度的影响，光斑后方呈收缩状应力带。数值模拟熔覆层形貌与实验一致，显微组织形态符合快速凝固原理的变化规律，验证了模型的有效性，熔覆层硬度明显高于基体，约为基体的1.6倍。结论 数值模拟揭示了温度场、流场、塑性应力场瞬态演变规律，实验表明激光熔覆IN625合金粉末可有效改善球墨铸铁件的表面质量，提高其力学性能。

Laser cladding is an emerging environment-friendly advanced manufacturing technology that effectively solves the defect repair and strengthening of the nodular iron castings, improving hardness and wear resistance, and prolonging service life. Due to the strong heterogeneity of nodular iron structure and chemical composition, complicated cladding process caused by the carbon diffusion of the graphite phase, and the limited selection of cladding powder. It is difficult to obtain the transient evolution law of multi-field coupling in the cladding process only by material science experiments. Therefore, in this paper, numerical modeling and experimental analysis are combined to study the transient evolution mechanism of IN625 laser cladding on QT600 nodular iron.