Revealing the microscopic material removal process and mechanism of electrical discharge machining of silicon carbide: A molecular dynamics study

Abstract

Electrical discharge machining (EDM) presents strong potential as a preferred machining process for silicon carbide (SiC) wafers due to its thermal removal mechanism, which is not constrained by the high hardness and brittleness of SiC. Furthermore, its cost-effectiveness enhances its feasibility for industrial applications. Therefore, a thorough understanding the material removal mechanisms of SiC in EDM is crucial for enhancing machining efficiency and improving surface quality. However, the above mechanisms are difficult to reveal due to the complexity of the machining process. To address this issue, a molecular dynamics (MD) model is developed in this study to investigate the material removal process and the formation of discharge craters at the micro-scale during the EDM of SiC. The results showed that different from ordinary metal materials, chemical changes such as thermal decomposition reaction and combination reaction, as well as physical changes such as gasification, melting and peritectic reaction occur in the EDM of SiC, generating the elemental carbon (C), elemental silicon (Si), and carbon-silicon compound (Si_xC_y). The removed material includes a significant amount of Si_xC_y gases, C vapor, Si vapor, and molten Si_xC_y. After discharge, the surface of the discharge crater mainly contains a large amount of amorphous Si_xC_y with a small amount of amorphous C and amorphous Si. The amorphous Si_xC_y and amorphous C collect on the surface of the discharge crater to form particles causing rough surface. Additionally, a large amount of thermally decomposed material, which is not removed, re-solidifies on the surface of the SiC during EDM, limiting machining efficiency and deteriorating surface quality. This study enhances the understanding of the material removal mechanisms of SiC during EDM, providing a foundation for the optimization of processing techniques.