Structure defect prediction of single crystal turbine blade by dendrite envelope tracking model
(1.School of Materials Science and Engineering; State Key Laboratory. of Materials Modification by Laser, Ion and Electron Beams, Dalian University of Technology, Dalian 116024, China
2.Graduate School of Engineering, Osaka University, Osaka 565-0871, Japan
3.School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China)
2.Graduate School of Engineering, Osaka University, Osaka 565-0871, Japan
3.School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China)
Abstract: The structure defects such as stray grains during unidirectional solidification can severely reduce the performance of single crystal turbine blades. A dendrite envelope tracking model is developed for predicting the structure defects of unidirectional solidification turbine blade. The normal vector of dendrite envelope is estimated by the gradient of dendrite volume fraction, and the growth velocity of the dendrite envelope (dendrite tips) is calculated with considering the anisotropy of grain growth. The solute redistribution at dendrite envelope is calculated by introducing an effective solute partition coefficient. Simulation tests show that the solute-build-up due to the rejection at envelope greatly affects grain competition and consequently solidification structure. The model is applied to predict the structure defects (e.g. stray grain) of single crystal turbine blade during unidirectional solidification. The results show that the developed model is reliable and has the following abilities: reproduce the growth competition among the different-preferential-direction grains; predict the stray grain formation; simulate the structure evolution (single crystal or dendrite grains).
Key words: turbine blade; single crystal; stray grain; dendrite envelope tracking; modeling