Characterization of plastic deformation induced by machining in a Ni-based superalloy

The surface integrity characteristics of Udimet 720Li subjected to slight damage and damage machining conditions have been studied using a complementary range of techniques such as FIB-SEM, EBSD, TKD, TEM-EDS and nano-indentation. The results indicate the existence of nano-sized grains and no observable tertiary gamma' in regions of severe plastic deformation in the machined surface. The correlation between the machining condition and the resulting plastic deformation is established. Grain refinement of this alloy via machining was achieved by dislocation slip. The nanohardness of the surface of damage machined sample is 40% higher than that of bulk material, which is attributed to the formation of nano-sized grains and high density of dislocations in the superficial layer.