As an advanced ceramics material, silicon carbide (SiC) is extensively applied in numerous industries. In this study, molecular dynamics method is used to comparatively investigate the nanomachining mechanism between monocrystalline SiC (mono-SiC) and polycrystalline SiC (poly-SiC) ceramics. Four simulations are performed for the two materials with and without ultrasonic vibration-assisted machining (UVAM). The diamond tool is set as a non-rigid body and vibrated along the depth direction with 100 GHz in frequency and 0.5 nm in amplitude. The effects of material and ultrasonic vibration on the nanomachining mechanism of SiC are analyzed in depth, including the surface generation, subsurface damage, and tool wear. It is determined that the machinability of SiC ceramics can be effectively improved by UVAM. The machining-induced damage extent of poly-SiC is more serious than that of mono-SiC. It is also found that UVAM can effectively reduce the machining-induced damage, decrease the machining resistance, and increase the possibility of ductile removal, but bring about a slightly larger tool wear.

As a typical third-generation semiconductor material, silicon carbide (SiC) has been increasingly used in recent years. However, the outstanding performance of SiC component can only be obtained when it has a high-quality surface and low-damage subsurface. Due to the hard–brittle property of SiC, it remains a challenge to investigate the ductile machining mechanism, especially at the nano scale. In this study, a three-dimensional molecular dynamics (MD) simulation model of nanometric cutting on monocrystalline 3C-SiC was established based on the ABOP Tersoff potential. Multi-group MD simulations were performed to study the removal mechanism of SiC at the nano scale. The effects of both cutting speed and undeformed cutting thickness on the material removal mechanism were considered. The ductile machining mechanism, cutting force, hydrostatic pressure, and tool wear was analyzed in depth. It was determined that the chip formation was dominated by the extrusion action rather than the shear theory during the nanocutting process. The performance and service life of the diamond tool can be effectively improved by properly increasing the cutting speed and reducing the undeformed cutting thickness. Additionally, the nanometric cutting at a higher cutting speed was able to improve the material removal rate but reduced the quality of machined surface and enlarged the subsurface damage of SiC. It is believed that the results can promote the level of ultraprecision machining technology.

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