Study on subsurface layer of nano-cutting single crystal tungsten in different crystal orientations.

• The dislocation nucleation and movement realize the plastic deformation. • The [1 1 0] cutting obtained the best surface and subsurface quality. • Some defects such as atomic clusters, two types of dislocations occur in subsurface. • 1/2 〈1 1 1〉 dislocations merge into stable 〈1 0 0〉 dislocation for the [1 0 0] cutting. The subsurface damage of micro-nano components and high-precision surface affects the reliability and service life of the workpiece. In this study, the nano-cutting molecular dynamics simulation model of single crystal tungsten in different crystal orientations was carried out to investigate the changes of crystal structure and dislocation evolution. The result showed that the dislocation nucleation and movement inside the workpiece lead to the defects such as atomic clusters, stair-rod dislocation and "V-shaped" dislocation. By cutting along 〈1 1 0〉, the best surface quality, the minimum subsurface defect layer depth and the greatest elastic recovery of defect layer can be obtained. During the different cutting process, there are two kinds of dislocation lines in the subsurface layer: 1/2 〈1 1 1〉 and 〈1 0 0〉. At the cutting direction of [1 0 0], 1/2 〈1 1 1〉 dislocation lines continuously merge into stable 〈1 0 0〉 dislocation lines, resulting in a sharp fluctuation of dislocation density. When the cutting directions are [1 1 0] and [1 1 1], 1/2 〈1 1 1〉 dislocation lines play an important role in plastic deformation, and the proportion of dislocation merging reaction is very small. This study reveals the formation mechanism of damage layer in ultra-precision cutting of single crystal tungsten from the atomic scale and provides a technical guidance for improving subsurface damage. [ABSTRACT FROM AUTHOR]