A new electrocatalytic oxidation flexible polishing method for consistent processing of RB-SiC

Abstract

Composite materials are widely utilized in extreme service environments because of their excellent mechanical properties. Reaction-bonded silicon carbide (RB-SiC), a representative example, is extensively used in ultra-precision optical mirrors and optical support structures. However, the high hardness, brittleness, and heterogeneous multiphase microstructure of RB-SiC result in notable challenges, primarily caused by the inconsistent removal rates of the SiC and Si phases due to the large disparity in their mechanical properties. Given that the inconsistent surface topography of composites can greatly degrade their performance in diverse applications. To address this issue, this study proposes an electrocatalytic oxidation flexible polishing (EOFP) method for the consistent processing of RB-SiC. Critical process parameters are optimized through the utilization of an orthogonal experimental design and a process study. Under optimal conditions, the material removal rate well matches the modification rate, which enable constant material removal. Surface roughness (Sa) of 0.23 nm and 0.504 nm are achieved for SiC and Si phases, respectively, and the interphase height difference (Hd) is reduced by an order of magnitude. This substantial surface quality improvement demonstrates the effectiveness of electrocatalytic oxidation flexible polishing for the consistent processing of RB-SiC, revealing that our study provides valuable guidance for other composite materials and holds promise for aerospace and other high-end applications.