Episodes of single-crystal material removal mode and machinability in the micro-cutting process of superalloy Inconel-718

The development tendency of miniaturization gives birth to the demand for Inconel-718 miniature parts, and micro-cutting is a promising technique to produce crystalline material miniature parts. Unfortunately, due to the non-negligible edge radius and property anisotropy, the material deformation behaviour and removal mode vary with cutting conditions, resulting in volatile machinability and inferior quality, which hinders the widespread application of Inconel-718 miniature parts. Therefore, it is urgent to clarify the evolution of material removal mode and machinability of Inconel-718 micro-cutting. Existing researches fail to consider the property anisotropy, strain-rate sensitivity and strain-rate inhomogeneity. This paper establishes strain rate-considered single-crystal micro-cutting models and performs simulations under varying cutting conditions, aiming to depict the episodes of material removal mode and machinability of Inconel-718 micro-cutting. Results show that, uncut chip thickness and cutter rake angle influence the material removal mode, and in turn influence machinability. For Inconel-718 single-crystal with [0° 0° 0°] orientation, the transition from the scratching mode to the ploughing mode is in the uncut chip thickness range of 0.2Re∼0.4Re, and the transition from the ploughing mode to the cutting mode is in the uncut chip thickness range of 0.6Re∼0.8Re or the rake angle range of −30°∼-15°. In comparison, cutting speed and clearance angle have little effect on material removal mode. Cutting speed influences the strain rate of the cutting-affected zone, and in turn influences machinability. The maximum strain rate of the cutting-affected zone is respectively around 0.45 s−1 and 10,960 s−1 under the cutting speeds of 2Re/s and 20000Re/s.