Spatial Control of Crystal Texture

Single-crystal blades have proven to have longer thermal and fatigue life, and can be directly fabricated by laser with thinner walls. However, the benefits of single-crystal over conventionally cast and directionally solidified components critically depend on avoiding the introduction of casting defects, such as stray grains, freckles, or deviations from the required crystal orientation. Laser-based direct metal deposition (DMD) process has demonstrated that it can fabricate fully functional metal prototype parts, repair industrial tooling, die casting and forging, and restore wear resistant and corrosion resistant surfaces for turbine blades. The DMD process equipped with proper sensors and numerically controlled devices can help in overcoming those hurdles to fabricate the blades. Not only thermal control to provide uniform heat flow, but spatial control of crystal texture of the blades by feedback control devices is also essential. The goals of proposal are, (1) to establish DMD process conditions and seed grain requirements for secondary grain growth for Ni-based superalloy, (2) to develop and demonstrate a laboratory scale DMD process for spatial control of crystal texture, (3) to develop a process model utilizing phase-field method to describe how spatial control of crystallographic texture affects the performance of Ni-based superalloy turbine blade rotating components.