Experimental characterization of plane and conformal hydrodynamic polishing of machined single crystal sapphire

Sapphire is an important ceramic material which finds applications in optics, electronics, and ceramic bearings. Chemical-mechanical polishing of sapphire is usually carried out for superfinishing. However, this paper reports a hydrodynamic polishing (HDP) approach. It involves deterministic flow of abrasive particles in the slurry between the workpiece surface and a rotating low elastic modulus tool. A novel experimental setup has been fabricated to realize the conformal HDP on single crystal sapphire cavity. The experimental results in flat and conformal nanopolishing show an improvement of 25–70% in the surface finish over the PCD hard-turned surfaces.