In Situ Diagnostics of Damage Accumulation in Ni-Based Superalloys Using High-Temperature Computed Tomography

The design, operation, and performance of a laboratory-scale X-ray computed tomography arrangement that is capable of elevated-temperature deformation studies of superalloys to 800 degrees C and possibly beyond are reported. The system is optimized for acquisition of three-dimensional (3D) backprojection images recorded sequentially during tensile deformation at strain rates between 10(-4) and 10(-2) s(-1), captured in situ. It is used to characterize the evolution of damage-for example, void formation and microcracking-in Nimonic 80A and Inconel 718 superalloys, which are studied as exemplar polycrystalline alloys with lesser and greater ductility, respectively. the results indicate that such damage can be resolved to within 30 to 50 mu m. Collection of temporally and spatially resolved data for the damage evolution during deformation is proven. Hence, the processes leading to creep fracture initiation and final rupture can be quantified in a novel way.