Micro-/nano- structures in subsurface of a new-generation single-crystal blade tenon following ultrasonic vibration-assisted grinding

Ultrasonic vibration-assisted grinding (UVAG) is a promising approach for the challenging machining of single-crystal blade tenons. However, there has been limited research on the subsurface properties of single-crystal superalloys after UVAG. This study addresses this gap with a detailed investigation. The results show that, compared with conventional grinding (CG), UVAG produces a smoother edge on the blade tenon, thanks to the intermittent cutting action of abrasive grains caused by ultrasonic vibration. The plastic deformation layer at the apex of the blade tenon tooth was approximately 2.55 times thicker than that at the valley because of uneven thermal coupling loads. Theoretical analysis revealed that the plastic deformation layer in the fourth deformation zone (2.05 μm vs. 2.48 μm) was thinner under UVAG than under CG. Both the matrix and strengthened phases exhibited regular elongation and distortion in low-strain regions due to grinding forces. In contrast, in high-strain regions near the grinding surface, the phases broke into submicron crystals (200–400 nm) and distinguishable nanocrystals (10–40 nm). The microstructural deformation mechanism on the surface of the single-crystal blade involved crystal plane slip in low-strain zones and a transition from single crystals to polycrystals in high-strain zones.