Atomistic insights on the nanoscale single grain scratching mechanism of silicon carbide ceramic based on molecular dynamics simulation

Yao Liu,Lingfei Kong,Beizhi Li

doi:10.1063/1.5019683

Abstract

The precision and crack-free surface of brittle silicon carbide (SiC) ceramic was achieved in the nanoscale ductile grinding. However, the nanoscale scratching mechanism and the root causes of SiC ductile response, especially in the atomistic aspects, have not been fully understood yet. In this study, the SiC atomistic scale scratching mechanism was investigated by single diamond grain scratching simulation based on molecular dynamics. The results indicated that the ductile scratching process of SiC could be achieved in the nanoscale depth of cut through the phase transition to an amorphous structure with few hexagonal diamond structure. Furthermore, the silicon atoms in SiC could penetrate into diamond grain which may cause wear of diamond grain. It was further found out that the chip material in the front of grain flowed along the grain side surface to form the groove protrusion as the scratching speed increases. The higher scratching speed promoted more atoms to transfer into the amorphous structure and reduced the hexagonal diamond and dislocation atoms number, which resulted in higher temperature, smaller scratching force, smaller normal stress, and thinner subsurface damage thickness, due to larger speed impaction causing more bonds broken which makes the SiC more ductile.

Highlights

Silicon carbide (SiC), one of the most commonly used ceramics, is widely utilized in industry, such as automotive, aerospace, aviation, laser machine, and nuclear energy, due to the low density, chemical stability, and high hardness.[1]
Molecular dynamics (MD) simulations of nanoindentation of cubic silicon carbide (β-SiC) by a diamond tip were conducted by Noreyan et al.[29] to study the dependence of elastic-to-plastic transition on indentation velocity, tip size, and workpiece temperature, the results indicated the critical depth for the elastic-to-plastic transformation of β-SiC depends only weakly on the indentation velocity and workpiece temperature
More silicon atoms are shown in the cross-section view of Y=7.5 nm due to the deformation caused by scratching force

Summary

Introduction

Silicon carbide (SiC), one of the most commonly used ceramics, is widely utilized in industry, such as automotive, aerospace, aviation, laser machine, and nuclear energy, due to the low density, chemical stability, and high hardness.[1]. The crack in the surface/subsurface may result in the strength degradation and failure of the SiC ceramic parts in the working process.[2,3] the understanding of the SiC crack-free material removal mechanism has a significant contribution to achieve the high-quality ground surface and broaden the application range of SiC ceramic. Ductile grinding, which is though as the alternative solution for the SiC crack-free machining process, has been achieved in the experiment when the depth of cut is in sub-microscale or nanoscale. The feasibility of ductile regime machining of SiC in single diamond cutting was first reported in 2005.4 The diamond turning of single-crystal 6H-SiC was performed by Goel et al.[5] to investigate the ductile-regime machining, tremendously high cutting resistance was offered by SiC resulting in significant wear on the cutting tool after 1 km of cutting length. The material removal mechanism of SiC in nanoscale undeformed chip thickness compounded with slow feed rate was believed to be helpful for achieving high-pressure phase transformations

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Conclusion