In Situ Mechanics of Ni-based Superalloys and Bond Coating

High-strength structural materials such as Ni-based superalloys and diffusion bond coats are widely used in challenging environments and with exposure to mechanical fatigue, particle impact, and erosion at elevated temperatures. Diffusion aluminide bond coats are an example of compositionally and microstructurally graded coatings with significant variation in engineered mechanical properties across the cross-section. Nanoindentation and pillar compression, particularly in situ, can be considered as a well-suited technique for measuring the properties of such complex microstructural materials as the deformation volume can be carefully controlled to probe different precipitates and microstructural zones. In this study, an SEM nanomechanical instrument with an integrated high-temperature stage and an active tip heating was used to conduct pillar compression of aluminide bond coating and substrate at room temperature to well above 800degC. This is the first study of an in situ nanomechanical testing of any sample at such higher temperature with capturing deformation events in detail at that temperature inside an SEM. With combined analysis of chemistry and microstructural changes, the results were used to understand local mechanical properties variation as a function of temperature.