Ultrasonic vibration-assisted polishing of V-groove arrays on hard and brittle materials

Silicon carbide (SiC) and binderless tungsten carbide (WC) with the excellent mechanical and physical properties are promising mold materials in glass molding of microstructured optical elements. However, the high microstructured surface quality can be hardly generated by grinding because of the high hardness and brittleness of SiC and WC. In this article, the ultrasonic vibration-assisted polishing was carried out aiming to improve the V-groove arrays' surface quality. The angle of the polishing wheel's V-shape section was first corrected to avoid rounding the tops of the V-grooves. And then the correction of the profile of the polishing wheel's V-shape section was investigated to maintain the profile accuracy of the V-grooves. Finally, the grating array and pyramid array were polished on SiC and WC by introducing the ultrasonic vibration. The experimental results indicate that after corrected the angle of the polishing wheel's V-shape section, the arc radius R of the top corner is reduced from 12 to 5 μm. The maximum profile deviation of the V-groove polished by the polishing wheel with no corrected profile is 1.0487 μm, while through polished by the polishing wheel with corrected profile, the maximum profile deviation is only 0.1768 μm with a factor of six times improvement. Furthermore, ultrasonic vibration-assisted polishing could bring a better grating and pyramid surface quality on SiC and WC than through grinding. The edges and tops of the V-groove are sharp and without damage by ultrasonic vibration-assisted polishing.