重型燃机定向结晶空心叶片凝固过程的实验与模拟

采用ProCAST软件系统研究HRS(High Rate Solidification)与LMC(Liquid Metal Cooling)工艺下,不同工艺参数对重型燃机用大型定向结晶空心叶片凝固过程的影响。结果表明:与HRS工艺相比,LMC工艺下叶片的糊状区宽度更小,固/液界面形状更加平直。LMC工艺下叶片的纵向温度梯度约为HRS工艺下的3倍;利用LMC工艺制备该燃机叶片时冷却速率为0.3~2.00℃/s,远高于HRS工艺时的冷却速率(0.05~0.16℃/s);LMC工艺下,采用低的保温炉温度仍可保证叶片获得高的温度梯度和冷却速率;而为避免缘板处杂晶对原始晶粒的阻碍,HRS工艺应当采用高的保温炉温度与更低的抽拉速率。实验与模拟结果均表明:与HRS工艺相比,利用LMC工艺制备的燃机叶片,枝晶组织显著细化。

Simulation and Experiment of Solidification Process for Directionally Solidified Industrial Gas Turbine Hollow Blades

The effect of different process parameters on solidification of industrial gas turbine hollow blades via HRS (High Rate Solidification) and LMC (Liquid Metal Cooling) was studied by ProCAST software.The results show that the paste zone via LMC process is much narrower than that by HRS process and the shape of the S/L (solid/liquid) interface is more flat.The axial thermal gradient of the blade by LMC process is about three times higher than that by HRS process.The cooling rate of the blade is 0.3-2.00℃ /s by LMC process,which is far higher than that by HRS process (0.05-0.16℃/s).In LMC process,low holding temperature can still ensure high temperature gradient and cooling rate of the blade;while in order to avoid blocking of stray grains to the initial grains at the platform of the blade,HRS process should adopt high holding temperature and lower withdrawal rate.The calculated and the measured results show that compared with the blade prepared by HRS process,the PDAS (primary dendrite arm spacing is much finer in the blade prepared by LMC process.