重燃叶片定向凝固宏/微观数值模拟及实验研究

Macro-micro Numerical Simulation and Experiment of Directional Solidification for Industrial Gas Turbine Blade

通过模拟和实验的方法对比研究了重燃叶片定向凝固过程宏观温度场及微观组织的变化规律。建立了非均匀网格的求解模型,提高了计算效率。基于温度场的模拟结果分析了糊状区的演化规律。采用线性插值算法结合元胞自动机有限差分(cellular automaton finite difference,CAFD)模型模拟了叶片的微观组织,并和实验进行了对比,模拟和实验结果吻合良好。讨论了几种常见晶粒缺陷产生的原因,提出了预防措施。采用电子背散射衍射(electron backscattered diffraction,EBSD)技术进一步探讨了晶粒的竞争生长行为。建立了枝晶臂间距的计算模型,模拟了叶片的枝晶臂间距分布,并进行实验观察,分析了枝晶臂间距的变化规律。从宏、微观的角度解释了叶片的凝固特征,为实际生产提供帮助。

Directional solidification process of industrial gas turbine blades（IGTs） was studied based on temperature field and the microstructure was investigated by both simulation and experimental methods. A mathematical model of nonuniform meshes was built to compute temperature field, which improves the computation efficiency. The evolvement rule of mushy zone was analyzed based on simulation results of temperature field. Interpolation algorithm and cellular automaton finite difference（CAFD） model were used to predict the microstructure growth of IGTs. Pouring experiments were carried out, and experiment results agree well with simulation results. Combined with electron backscattered diffraction（EBSD）, some common defects of castings were analyzed, and the corresponding prevention measures were put forward. Primary dendrite arm space（PDAS） and secondary dendrite arm space（SDAS） were calculated considering the influence of solute diffusion and solidification rate, and dendrite morphology was observed by optical microscopy（OM）. The results reveal that PDAS and SDAS change in different transverse sections of IGTs. The solidification characteristics of IGTs were studied through macro and micro perspective in order to provide help for industrial production.