Feasibility of using wet abrasive jet machining to produce flat and crack-free micro-textures on reaction bonded silicon carbide

Reaction-bonded silicon carbide (RB-SiC) is a composite ceramic that comprises of hard SiC grains and brittle Si matrix. Surface texture with well machining qualities, in particular, is difficult to be fabricated on RB-SiC in conventional machining conditions since the removal of material inevitably induces some unexpected surface defects. In this paper, the feasibility of using a wet abrasive jet machining process (wet AJM) to produce smooth and crack-free micro-features on RB-SiC was investigated. Three commercial abrasives were employed to test the machining responses. The hardness of abrasive was found to be critical and dominate the machinability of RBSiC. The hardest synthetic diamond (SD) abrasive could crush the SiC grains, thereby providing the highest machining efficiency and a relatively smooth face. The relatively soft abrasives, including aluminum oxide (Al2O3) and green SiC, tend to break or rebound during the impact. After removing the Si matrix, SiC grains would be exposed and be to some degree protective of the target; therefore, the machined texture was shallow and rough. Since the particles in the lateral flow rolled freely, there were no obvious cracks on the inner surface of the machined texture compared to the machining without water. The variation of the machining profile had an inherent correlation to the mask thickness, nozzle motion speed and particle size. With these optimized parameters, it is feasible to use the wet AJM to fabricate complex micro-structural arrays on RB-SiC with good precision and surface quality.