Probabilistic Prediction of Location-Specific Microstructure in Turbine Disks

Turbine efficiency improves with increased operating temperature. Consequently, the rim zone of disks operates at high temperatures where creep is the main concern. The bore and web zones operate at lower temperatures, where strength is the driving design criterion. Procedures to produce disks that can meet both demands include dual heat-treatment and hybrid disks. A thin transition zone forms in disks produced with either of these technologies, which is characterized by location-specific three-dimensional microstructure and residual bulk stresses. The objective of this project is to enable the optimization of advanced nickel-base superalloy turbine disks by developing probabilistic modeling and simulation methods to predict location-specific microstructure and bulk residual stresses. Symplectic Engineering is proposing to develop a multi-scale model to meet this objective. The global (disk) scale will be represented as a coupled thermal-mechanical system, approximated by a three-dimensional finite elements model. A number of models will be combined to produce the local-scale representation including gamma-prime coarsening and grain growth. The two scales will interact independently at each Gauss point of the global-scale finite element mesh. The performance of the proposed model will be demonstrated by simulating the forging of a dual heat-treated disk, and contrasting the prediction with experimental data.