OBRABOTKAMETALLOV Vol. 26 No. 4 2024 TECHNOLOGY Ta b l e 9 A family of optimized process parameters for NFMQL cutting conditions Sr. No. Cutting speed (V) (rpm) Feed (f) (mm/rev) No. of passes Surface roughness (Ra) (μm) Microhardness (HV) Roundness error (Re) (μm) Desirability 1 357.6 0.17 3.68 0.6435 130.1976 3.519 0.8417 2 357.64 0.16 3.68 0.6436 130.1916 3.515 0.8417 3 357.81 0.16 3.68 0.6436 130.1988 3.514 0.8417 4 357.68 0.17 3.68 0.6436 130.2047 3.518 0.8417 5 357.85 0.16 3.68 0.6436 130.1997 3.515 0.8417 6 357.67 0.16 3.68 0.6436 130.1962 3.515 0.8417 As can be seen, roller burnishing under NFMQL cutting conditions gives reduced values for surface roughness, roundness error, and maximum microhardness compared to dry conditions. The lowest surface roughness found was 0.64 μm. However, this study highlights the need for additional investigation on roller burnishing of Al6061-T6 alloy to obtain improved fi nished work geometries that approach surface roughness of up to 0.3–0.4 μm with increased microhardness. Conclusions In the present work, an attempt is made to investigate the roller burnishing of Al6061-T6 alloy. In this study, the roller burnishing of Al6061-T6 alloy in dry condition and using nanofl uid under minimum quantity lubrication (NFMQL) conditions is comparatively evaluated. The study evaluates, simulates and optimizes the microhardness, roundness and surface roughness by considering the factors such as cutting speed, feed and number of passes. Based on the experimental results, mathematical models are developed to predict the surface roughness, microhardness and roundness error. The following conclusions can be drawn: ● R-square value above 0.9 was observed for the surface roughness, microhardness and roundness error models that represent the developed models and can be reliably used to predict the studied responses under dry and NFMQL cutting conditions and within the domain of the parameters selected in the present study. ● Roller burnishing under NFMQL cutting conditions gives reduced values of surface roughness (0.64 μm), roundness error (3.514 μm) and maximum microhardness (130.19 HV) compared with dry conditions. However, roller burnishing under dry cutting conditions gives comparatively higher surface roughness (0.807 μm), roundness error (4.282 μm) and lower microhardness (119.2 H reduced). ● Surface roughness is observed to decrease with increasing cutting speed. However, it increases with increasing cutting speed to 360–380 rpm under both dry and NFMQL cutting conditions. Furthermore, it is observed to decrease with increasing feed and number of passes. However, after three to four passes with a feed of 0.2–0.25 mm/rev, an increase in surface roughness is noticeable. ● Microhardness and roundness error increase with increasing feed. And an increase in microhardness and a decrease in roundness error are observed with an increase in the number of passes. ● Increasing feed is seen to result in inconsistent responses for surface roughness and microhardness. A compromise between roundness error and microhardness and lower surface roughness is obtained using a feed value in the range of 0.18-0.22 mm/rev. It is observed that roundness error decreases with higher pass counts and maximum microhardness was observed with higher number of passes. ● Surface roughness is signifi cantly aff ected by the feed under NFMQL cutting conditions and the number of passes under dry conditions. Microhardness appears to be the most aff ected by cutting speed, with feed and number of passes coming in second and third. However, this eff ect appears to be more
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