Investigation of boring on gunmetal in dry, wet and cryogenic conditions

Abstract

Secondary operation of boring is carried out to produce close geometric tolerance holes produced in drilling. In this work, an attempt has been made in producing a hole by dry boring, wet boring and cryogenic boring of gunmetal. Gunmetal finds its application in areas of casting, steam turbines and pressure valves, due to its high resistance to corrosion. Investigation of cutting temperature generated during machining, cutting force experienced by the tool and surface roughness of the machined workpiece was toted out with analogous to cutting speed and feed, by Taguchi, ANOVA and TOPSIS analyses. Surface morphology study, tool wear analysis, residual stress analysis were done in order to distinguish the modification in the bored surface and tool material after machining. Cryogenic boring of gunmetal reduced the cutting temperature by 63.43% and 53.85% over dry boring and wet boring, respectively. Furthermore, cutting force is reduced by 34.51% and 18.29% over dry boring and wet boring, respectively. Additionally, a decrease of 62.23% and 35.10% is observed in surface roughness on comparing dry boring and wet boring with respect to cryogenic boring of gunmetal. Taguchi and ANOVA arbitrated speed as an imperative parameter for cutting force and feed as a paramount parameter in cutting temperature. Furthermore, speed is a crucial parameter for arbitrating surface roughness in dry boring and wet boring, additionally feed for surface roughness in cryogenic boring condition. TOPSIS analysis illuminated speed of 1200 rpm and feed of 0.055 mm/min as the most closest to exemplar elucidation for all three cutting preconditions. Aggrandizement in compressive residual stress is discerned in cryogenic boring by 39.74% and 19.35% correlated with dry boring and wet boring, respectively, as the material undergoes work hardening. A decrease in residual tensile stress is espied in cryogenic boring when juxtaposed to wet boring, ensuring upsurge in tool life and better surface characteristics. Microhardness in cryogenic boring of gunmetal improves by 5.83–11.05% and 0.51–2.57% analogous to dry boring and wet boring, respectively. Corrosion resistance in cryogenic boring increases by 77.43% and 49.25% analogous to dry boring and wet boring of gunmetal, respectively. The circularity and cylindricity increase by 4.76–98.40%, 8.33–97.50% and 6.25–97.15%, 2.43–92.85% in cryogenic boring juxtaposed to dry boring and wet boring of gunmetal, respectively.