Method of Stray Grain Inhibition in the Platforms with Different Dimensions During Directional Solidification of a Ni-Base Superalloy

Abstract

A model of typical turbine blade shape with different platforms was designed to study the method of stray grain inhibition in the platforms by both experimental investigation and a ProCAST simulation based on a Cellular Automaton Finite Element model. The results show that stray grains with random orientations increasingly nucleate and grow in these platforms with the increase of platform dimension. To inhibit these stray grains, assistant bars are designed to introduce the primary grain into these platforms according to the theory of seeding method. The results indicate by the help of these assistant bars, the primary grain is introduced to the large dimensional platforms by developing secondary and tertiary dendrites, which form “crisscross” structure in these platforms. And, the stray grains in the large dimensional platforms are successfully and effectively inhibited. Further more, it is found that the thermal condition and the solidification sequence are changed in the large dimensional platforms by the use of assistant bars, which result in the introduction of primary grain and the inhibition of stray grains. Besides, the simulation results are in accordance with experimental findings.