为了研究激光熔覆过程中熔池内的温度场特征及其对凝固后的微观组织的影响, 建立了描述熔覆过程的对流扩散固液相变统一的数学模型, 模拟了激光熔覆过程中熔池在不同时刻的温度场和速度场, 计算出熔覆层内不同位置的温度梯度、冷却速度和凝固速度。计算结果表明, 熔池内液体的流动对熔池内温度场分布有较大影响。距离熔覆层顶部越远, 冷却速度减小, 温度梯度增大, 凝固速度减小。这种温度场特征决定了从熔池底部到顶部的凝固组织类型及组织大小的变化特征, 并据此对熔覆层的凝固组织类型进行预测, 与实验结果吻合良好。

In order to study the characteristics of temperature field and its effect on the microstructure after solidification in the laser cladding process, a mathematical model describing the uniformity of the convective diffusion solid-liquid phase transition during the cladding process was established. The temperature and velocity fields of the molten pool during the laser cladding process was simulated. The temperature gradient, the cooling rate and the solidification rate of different locations in the cladding layer at different times were calculated. The results show that the flow of liquid in the molten pool has a great influence on the temperature field distribution in the molten pool. The farther away from the top of the cladding layer, the slower the cooling rate and the solidification rate, but the higher the temperature gradient. This feature of the temperature field determines the characteristics of the solidification type and size of the microstructure from the bottom to the top of the molten pool. Predictions for the solidification type of the microstructure were made and coincided well with the experimental results.