Grain refinement mechanism of metamorphic layers by abrasive grinding hardening

Abstract

The abrasive grinding hardening is not only a high precision material removal process, but also generates metamorphic layers to improve surface strength, which is affected by surface material grain size. As the grain size is decided by dynamic recrystallization phenomenon under grinding thermal-stain coupling, the grain refinement mechanism should be studied. The full scale thermal-strain coupled finite element method (FEM) considering wheel's profile and abrasive distribution is established firstly. Afterwards, the governing equation on the increase of dislocation density is set up by three dimensional cellular automata (CA). And the refinement process of metamorphic layers is modeled. Meanwhile, the influence mechanism of dynamic thermal-strain effect on austenite grain in metamorphic layers is studied. Finally, with the help of grinding experiments, the variation regulation on austenite grain size and its content along the surface layers is compared and validated under different feeding rates and grinding depths. The obtained conclusion can not only improve the transformation mechanism of metamorphic layers in abrasive grinding hardening, but also give a parametric reference for grain refinement in actual machining process.