Abstract
Nickel-based superalloys are widely used in the aerospace, automotive, marine and medical sectors, owing to their high mechanical strength and corrosion resistance. However, they exhibit poor machinability due to low thermal conductivity, high shear modulus, strain hardening, etc. Various modifications have been incorporated into existing machining techniques to address these issues. One such modification is the incorporation of ultrasonic assistance to turning operations. The assisted process is popularly known as ultrasonic assisted turning (UAT), and uses ultrasonic vibration to the processing zone to cut the material. The present article investigates the effect of ultrasonic vibration on coated carbide tool wear for machining Nimonic-90 under dry and wet conditions. UAT and conventional turning (CT) were performed at constant cutting speed, feed rate and depth of cut. The results show that the main wear mechanisms were abrasion, chipping, notch wear and adhesion of the built-up edge in both processes. However, by using a coolant, the formation of the built-up edge was reduced. CT and UAT under dry conditions showed an approximate reduction of 20% in the width of flank wear compared to CT and UAT under wet conditions. UAT showed approximate reductions of 6–20% in cutting force and 13–27% in feed force compared to the CT process. The chips formed during UAT were thinner, smoother and shorter than those formed during CT.
Highlights
Nickel-based superalloys exhibit good mechanical strength and corrosion resistance.Due to their superior properties, they are used in aircraft gas turbines, power plants, engines, medical applications, space vehicles, etc
Some hybrid machining processes, such as ultrasonic vibration-assisted [2], inductionassisted [3], LASER-assisted [4], gas-assisted [5] and minimum quantity lubrication (MQL)assisted [6,7] machining are used to improve the machinability of those alloys
Comparative analysis of the tool wear of Nimonic-90 in ultrasonic assisted turning (UAT) and conventional turning (CT) has to be studied; (2) the mechanisms and behaviour of tool wear in UAT under dry and wet conditions need to be explored
Summary
Nickel-based superalloys exhibit good mechanical strength and corrosion resistance. Due to their superior properties, they are used in aircraft gas turbines, power plants, engines, medical applications, space vehicles, etc. Some characteristics such as work hardening during machining, localisation of shear in the chips and tendency of builtup edge (BUE) formation make them poor for machining These characteristics produce high temperatures and stresses and increase tool wear, cutting forces, power consumption, etc. Ultrasonic-assisted milling (UAM) of Al 6063 was performed by Verma and Pandey [12] and showed that vibration in the axial direction reduced average cutting force and increased standard deviation. Paktinat and Amini [17,18] performed ultrasonic-assisted drilling (UAD) of aluminium alloys to analyse burr formation, chips and surface quality of holes. (2) the mechanisms and behaviour of tool wear in UAT under dry and wet conditions need to be explored. An experimental study was performed under dry and wet conditions for UAT and CT processes using Nimonic-90 as the workpiece material to address the gaps as mentioned above.
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