Experimental characterization of hydrodynamic nanopolishing of flat steel plates

Nanoscale polishing finds applications in medical, industrial, telecommunication, optics, electronic and military fields. Typically, rigid tool-based methods such as diamond turning, grinding and honing are employed for nanoscale polishing. These methods have inherent limitations in creating nanopolished surfaces on hard and profiled surfaces. To address the issue, this work is focused on experimental investigation of hydrodynamic polishing (HDP) as a nanopolishing method. The soft rubber tool and the workpiece are submerged in a slurry during hydrodynamic nanopolishing. An elastohydrodynamic film is formed between the tool and the workpiece due to the tool rotation which is responsible for nanopolishing. A HDP experimental setup was fabricated and experiments were conducted on oil hardened and non-shrinking steel (OHNS, 58-62 HRC) with colloidal alumina suspensions of different particle sizes. The experiments were designed using Taguchi techniques to study the effect of four main factors (contact load, tool stiffness, spindle speed and abrasive particle size) and three important two-factor interactions at four different polishing times. Statistical analysis of the results shows that concentration of abrasive in the slurry is a significant factor in the hydrodynamic polishing. The best surface finish of 3.5 nm was obtained using 1 μm abrasive particle size colloidal suspension at 7.5 N load, 2400 rpm spindle speed, 90 shore A tool stiffness and 3 min of polishing time. The change in surface morphology and topography due to polishing also confirm the efficacy of the HDP process.