Analysis of Mechanochemical Reaction in Dual Shot Peening

Using a combination of solid mechanics and reaction kinetics models, this work simulates a mechanochemical reaction in dual shot peening with a mixture of Al₂O₃ and Cu₂S particles used to form a tribologically beneficial iron sulfide layer on treated surfaces. The model predicts that the dissociation of the Fe–Fe and Cu–S bonds needed for the formation of Fe–S bonds accelerates monotonically with an increase in the shot peening particle speed, whereas its rate reaches a local maximum at the impact angle of about 75 deg. The latter finding is validated by treating the rake faces of high-speed steel cutting tools and performing orthogonal cutting experiments in which the tools peened at the impact angle of 75 deg exhibit lower cutting and thrust forces than those peened at 40 deg. Additional peening parameters, namely, the particle volume ratio and the stage speed, are found to be much less statistically significant under the conditions tested. The developed approach may be instrumental in guiding process optimization to improve the tribological performance of mechanochemically treated surfaces.