物性参数温度变化下激光熔覆多场耦合模拟与实验

Multi-field Coupling Simulation and Experiment of Laser Cladding under Thermal Dependent Physical Properties

激光熔覆存在热-弹性-塑性-流体多场耦合变化,影响对流、传热和传质,同时影响凝固过程。因熔池体积小、温度变化梯度大、具有极强的瞬时性,难以用实验方法动态跟踪并揭示多场耦合演变机理。建立了碟片激光器在45号钢基体熔覆Fe60过程三维模型,考虑了粉光作用,熔池表面张力、浮力对液态金属流动的影响,熔覆带形状的瞬时变化,以CALPHAD相图计算法得出基体和粉材的温度变化物性参数,计算得出温度场、流速场的分布与演变规律。计算结果表明:模拟预测得出的激光熔覆形态和凝固组织与通过Zeiss-ΣIGMA HD型场发射扫描电镜金相实验结果相吻合。

The thermal-elastic-plastic-flow multi-field coupling changes exist in laser cladding,which affects convection,heat,mass transfer,and solidification process. The mechanism of multi-field coupling evolution is hard to be dynamically tracked and revealed because of the small volume of molten pool,large temperature gradient and very strong instantaneous characteristics. A multi-field coupled 3 D mathematical model of disk laser in the process of cladding Fe60 powder on 45 steel was established. The interaction between the powder flow and the laser energy beam,the influences of surface tension and buoyancy on the fluid flow in the melt pool,and the instantaneous change of cladding layer shape are taken into account in the proposed model. The thermal dependent physical properties of substrate and powder were obtained by using the CALPHAD phase diagram calculation method. The model was solved to obtain the distribution state and evolution law of temperature field and velocity field in the process of laser cladding.The results show that the laser cladding morphology and solidification microstructure predicted by simulation agree well with the metallographic results obtained by using Zeiss-IGMA HD field emission scanning electron microscope.