Plastic deformation and nano-cutting characteristics of nanocrystalline Ni-based superalloy

Molecular dynamics simulations of nano-cutting nanocrystalline Ni-based superalloy (NCNBS) were performed to investigate contact-induced plastic deformation and the mechanical characteristics. The results indicate that deformation in single crystalline workpieces is predominantly governed by dislocation slip, whereas deformation in nanocrystalline workpieces is attributed to the synergistic action of multiple mechanisms: (1) grain boundary (GB) sliding and migration, (2) GB expansion and cleavage cracking, (3) triple junction migration and rotation, (4) grain rotation and merging, (5) grain coarsening, and (6) nucleation and expansion of stacking faults and deformation twins originating at the machining surface and GBs. The grain refinement-induced reverse Hall-Petch effect results in significant reductions in surface roughness (−14.05%), thrust force (−17.27%), and average dislocation line length (−14.36%); however, it increases the friction coefficient by 14.29%. Furthermore, surface roughness, cutting forces, and friction coefficients exhibit strong correlations with cutting velocities and depths. Stress and strain primarily propagate along GBs, yet these GBs effectively inhibit their transmission along the original paths within grain interiors. Elevated cutting parameters (grain number, cutting velocity, and cutting depth) amplify both the values and affected areas of high stress and strain. The HCP generation rates decrease in lockstep with the cutting velocity, indicating velocity’s marked suppression of dislocation nucleation and expansion. These findings elucidate the atomic-scale material removal mechanisms in NCNBS and establish innovative frameworks for design optimization and parameter selection in ultra-precision component manufacturing.