Molecular Dynamics Simulation Investigation of Thermal Assistance Effects in Synchronous Thermally Assisted Scratching of Monocrystalline 4H-SiC

4H-SiC is a typical difficult-to-machine semiconductor due to its high hardness and anisotropy. Conventional abrasive machining is limited by subsurface damage (SSD) and tool wear. Thermally assisted machining offers advantages, but achieving thermal-mechanical coupling remains experimentally challenging. This study established a molecular dynamics (MD) model featuring synchronized contact between the heating zone and abrasive grains—simulated along the [ $$\overline{1}2\overline{1}0$$ ] crystal direction. The surface thermal power densities (Ps) were varied to investigate damage evolution, chip-debris morphology, machining forces, sliding friction coefficient (μ), dislocations, and SSD depth. Compared with conventional abrasive machining, at a critical Ps of 12.0 × 1011 W/cm2, μ, weighted mean of von Mises stress ( $$\overline{\sigma }_{vm}$$ ), and SSD depth decrease by 49.0, 28.3, and 67.6%, respectively. Sufficient thermal softening results in a $$\overline{\sigma }_{vm}$$ reduction in the deformation zone, which promotes plastic flow and surface amorphization. Energy dissipation is confined to the near-surface region, suppressing SSD propagation. This study provides atomic-scale insights for optimizing thermally assisted parameters to minimize SSD.