Numerical Simulation of Microstructure Evolution During Directional Solidification Process of DS Turbine Blades

Directional solidified (DS) turbine blades are widely used in advanced gas turbines. The sizes and growth orientations of columnar grains in these blades greatly affect properties and performances of the blades. Numerical methods provide effective ways to simulate the directional solidification process, to study the grain’s growth and morphology, and then to optimize the process.

A mathematic model was built to study the directional solidification microstructures at different withdrawal rates. Ray-tracing method was proposed to calculate temperature field and gradient, coupled with a Modified Cellular Automation method, the mushy zone and microstructure could be studied further. Validation experiments were carried out at different withdrawal rates. The cooling curves and microstructure results either from experiment or simulation corresponded well with each other. Therefore the calculated temperature gradient and mushy zone distribution could provide reasonable way to analyze and optimize the solidification process.

This study indicates that withdrawal rate affects temperature field and growth rate of the grain directly, which decides the size and morphology of the columnar grain finally. A moderate withdrawal rate can get high quality DS turbine blades for industry application.