Understanding of highly-oriented 3C-SiC ductile-brittle transition mechanism in ELID ultra-precision grinding

Abstract

Highly-oriented 3C-SiC possesses good out-of-plane orientation uniformity, and has more potential to obtain uniform surface quality during ultra-precision machining, compared with randomly-oriented SiC (such as RB-SiC and S-SiC, et al.). Through ultra-precision machining of highly-oriented 3C-SiC under electrolytic in-process dressing (ELID), the oxide film formed on the grinding wheel enhances the contact stiffness between the grinding wheel and the workpiece during the process. Further, compressive residual stress of 0.29 MPa on highly-oriented 3C-SiC surface conducive to the removal of material ductile was generated. It enabled ELID to perform better material ductile removal ability than conventional grinding (CG) does. On the other hand, numerous stacking faults (SFs) in highly-oriented 3C-SiC promoted the migration of dislocations in the material and generated more dislocations in the material under the shear stress of ELID grinding wheel. In addition, the accumulated dislocations at the grain boundary continued to slip to the next grain rather than resulting in dislocation pile-up and material crack due to the consistency of grain orientation. This phenomenon has the materials been ductile removal rather than brittle fracture. All above findings would provide a beneficial reference for the control of grinding process and the analysis of material removal mechanism of highly-oriented materials.