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The polishing process is used to produce a smooth surface with a required geometrical figure for the optical component. The abrasive slurry jet polishing process is one of the non-traditional polishing process, which is used to polish freeform optics with the nano-level surface finish. In the abrasive slurry jet polishing process, the saturation in surface roughness is observed with a jet exposure time or polishing time. Once the saturation limit is reached a further reduction in surface roughness without the modification of processing conditions and the size of the abrasive particles is not possible. Hence to achieve the required surface roughness a different polishing strategy has to be adapted. In this work, an attempt was carried out to yield a considerable reduction in surface roughness using a multistage polishing concept. In this concept, the impact angle, the traverse speed of the nozzle, the type and size of the abrasive particle were changed after the first stage of polishing. The surface generation has been studied by measuring the surface roughness at each stage of polishing, and the Scanning Electron Microscope (SEM) analyses have been done to understand the changes in surface texture, after polishing. From the experiments, the large size Al2O3 particle in the first stage of polishing and then small size Al2O3 particle in the remaining stages of polishing yields a considerable reduction in surface roughness. The combination of parameters with the type and size of the abrasive particles to be used to achieve the required surface characteristics were demonstrated. Thus, the multistage polishing concept can be floated as a viable strategy to achieve a high reduction in surface roughness on the optical component.

The poor machinability of super duplex stainless steels (SDSS) tends to generate detrimental tensile residual stresses that affect the service life of the component. Therefore, developing an efficient machining strategy to machine these components without any subsurface modifications is necessary. This work emphases on a detailed analysis of machinability and stress corrosion cracking resistance (SCC) of SDSS under different coolant environments (Dry, Flood, Minimum quantity lubrication). The cutting performance was evaluated using the machinability indicators such as tool wear, cutting force, surface finish, morphology of chips and residual stress. The chip morphology and residual stress results indicated that the thermally assisted deformation highly influences the machining of SDSS under all coolant environments. The overall machinability results revealed that MQL provided better performance than the other coolant and lubrication methods. To assess the SCC resistance, all the machined samples were subjected to SCC test under the chloride environment. The machined samples under MQL environment was observed with low surface crack density. This is due to presence of lower tensile residual stress with less surface defects. It was also observed that MQL samples exhibits lower localized corrosion (i.e) pit formation on the surface. These results clearly demonstrate that MQL is a recommended cooling and lubrication condition for the efficient machining of SDSS and to improve service life of the component.