Numerical simulation of the effect of scratching parameters and crystal orientation on the surface scratching mechanism of single-crystal γ-TiAl alloy

Abstract

The study investigated the effects of different tip radii and scratch depths of diamond conical indenter on the surface nano-scratching mechanism of single-crystal γ-TiAl alloys using Molecular Dynamics (MD) simulations. Effectively combining the scratching parameters with crystal orientation, the variation rules of temperature, mechanical response, atomic flow, subsurface damage, and surface morphology during the scratching process are revealed. The results demonstrate that increasing indenter tip radius and scratch depth lead to higher values of scratch force, temperature, and degree of subsurface damage. Moreover, the average coefficient of friction (COF) and removal rate of atomic wear increase with an increase in the ratio between scratch depth and indenter tip radius (d/r), also known as relative tool sharpness (RTS), a larger RTS facilitates generating more pile-up on both sides. In comparison, a smaller RTS concentrates chips at the indenter's tip. Furthermore, crystal orientation significantly influences the extent to which scratching parameters affect the matrix, specifically, the $\left(001\right)\left[\bar{1}\bar{1}0\right]$ crystal orientation exhibits higher scratch sensitivity. Finally, the optical morphology of the scratch was obtained by scratch experiment and qualitatively compared with the simulation results. The research results provide valuable insights for the selection of machining parameters of γ-TiAl alloy at nano-scale.