Cutting mechanism of reaction-bonded silicon carbide in laser-assisted ultra-precision machining

Abstract

Reaction-bonded silicon carbide (RB-SiC) is an important material used in aerospace optical systems. Due to the property mismatch between Si and SiC phases, the underlying cutting mechanism in ultra-precision machining of RB-SiC remains relatively unclear. Recently, laser-assisted machining (LAM) has emerged as an effective technique to improve the machinability of hard and brittle materials, which brings the question that how the high temperature affects the machining mechanism of RB-SiC. To elucidate these aspects, a series of grooving experiments and MD simulations were conducted in this study. The interaction mechanism between phases on material removal and subsurface damage was revealed and the effect of cutting temperature on Si-SiC interaction was explored. The results indicate that in conventional ultra-precision machining, SiC grains could affect the deformation of Si phase, whereas the influence of Si phase on SiC deformation is limited. As the cutting temperature increases, the Si-SiC interaction is less apparent and the deformation of Si and SiC becomes more independent. Meanwhile, the prominence of phase property mismatch on subsurface damage are reduced while the extension of disordered phases into boundaries merges as an important mechanism in subsurface damage formation. This research helps to understand the thermal effect on material interaction between phases during machining and aid to improve the performance of LAM on RB-SiC.