Simulation of Directionally Solidified Grain Morphology for Precision Casting of MAR-M-247LC Alloy and Its Experimental Verification

摘要

In this study, a computer simulation system is employed to predict the directional solidification behavior and subsequent grain morphology for a turbine blade investment casting of Mar-M-247LC alloy. Castings are then actually cast and the conditions of grain structure are compared to the simulated results to verify the accuracy of the computer simulation system. The computer simulation system in this study employs the finite element method to model the mold filling and solidification behavior and a stochastic model; named Cellular Automaton, to model the nucleation and grain growth behavior to predict the grain morphology of the directionally solidified casting. The casting under investigation is a complex hollow turbine blade with item dimensions of 53mmL*50mmH*15mmW. The casting design and operation include a top pouring gating system with twelve symmetric castings, preheat temperature of 1500℃, pouring temperature of 1500℃, and mold withdrawn speed of 7.5 mm per minute. Actual investment castings are then cast and their grain morphologies are examined. The grain morphologies to be investigated include grain numbers, grain orientations and grain sizes. As the simulated results are compared to the experimental measurements, good consistency is observed.