Effect of material composition on the action of surface active medium in ultra-precision microcutting

Ultra-precision diamond turning (UPDT) is an extensively adopted technology in optical applications owing to the nanometric surface finish and excellent form tolerance guaranteed on metallic materials. Coolants such as kerosene, isoparaffin etc. are broadly used in UPDT to reduce the friction at tool-workpiece interface for ultimately ensuring optical quality parts. However, the greater emphasis on sustainable manufacturing nowadays demand alternate approaches for minimizing cutting forces and improving the surface finish. The application of a surface active medium (SAM) over the workpiece surface prior to UPDT can be a befitting choice as it can induce Rehbinder effect on materials thereby minimizing cutting forces. Nevertheless, the performance of SAM in UPDT process with reference to material specific properties has not been widely explored in literature. The present study investigates the role of Rehbinder effect in controlling the material surface energy during UPDT of ductile materials. The surface integrity and force analysis indicate that the SAM action is significantly different for the parent metal (Cu) and alloy (Brass) under consideration. Moreover, the chip morphology inspection highlighted that SAM facilitates easier crack initiation and fracture in Cu unlike Brass. The results were further confirmed by conducting experiments on pure Zinc. Thus, the present study establishes the varying effectiveness of SAM towards material specific elemental composition.