We present a crystal plasticity (CP) model capable of predicting the creep behavior of T115-steel alloy and modified lab casts. Two differing heat treatments are performed to each alloy to enhance the creep behavior. Thermal treatments include a standard treatment with normalizing treatment followed by tempering and a non-standard, where the temperature is not lowered to RT between the normalizing and tempering. This non-standard treatment yields significantly different microstructure and thus creep behavior. Microstructural representative volume elements used to mimic the real microstructure are based on the statistics extracted from SEM-EBSD characterization of the casted material samples. To model the behavior of the material a thermomechanical CP-model capable of predicting the primary, secondary and eventually the material damage and thus the tertiary creep states. Damage is predicted both in modelling the damage evolution during the analysis and in post-processing. This ICME workflow enables the virtual design of creep resistant materials.