Investigation on mechanism of nano-machining of single-crystal silicon carbide on non-continuous surface with diamond abrasive

The molecular dynamics model of nano-machining a single-crystal silicon carbide substrate with a diamond abrasive is established. The effect of scratch on the atomic removal process and the material removal mechanism of the scratch wall were studied, considering vector displacement, cutting force, crystal structure transformation, and defects. The results show that the main methods for removing atoms in the scratched area are cutting and extrusion. The wall deformation of the scratch inlet zone invloves elastic and plastic mixed deformation, while the wall deformation of the scratch outlet zone is mainly plastic deformation. Increasing machining depth improves the removal of atoms. The presence of scratches on the substrate surface reduces both tangential and normal cutting forces in the nano-machining process, with the maximum difference being about 300 nN and 600 nN, respectively. The absence of atoms in the scratch area is the main reason for the decrease in tangential forces. The crystal structure of silicon carbide atoms is transformed by the shear and extrusion of the abrasive, resulting in a large number of atoms without a complete lattice. Moreover, atoms on the substrate surface form a stable structure by bonding with neighboring atoms. The affected area of substrate temperature is mainly concentrated under the abrasive and transferred to the depth of the substrate, with a difference of about 100 K between the substrate temperature at 2 Å, 5 Å, and 8 Å nano-machining depths.