Development of ultrasonic-vibration-laser assisted turning process to improve machinability of aluminium and magnesium alloys

Abstract

Cutting fluids are generally used during the conventional turning process to provide lubrication and flushing of chips from the cutting zone. However, cutting fluids cost around 16-20% of total production cost apart from coolant spray equipment and their disposal cost. Besides, cutting fluids are harmful to the operator and environment because in some cases it produces perilous, hazardous, and hydrogen gases that may explode. Thus, eco-friendly machining processes are desired in industries to eliminate cutting fluids apart from enhancing machining performance. Ultrasonic vibration assisted turning and laser assisted turning are advanced eco-friendly hybrid machining processes that have eliminated the usage of cutting fluids apart from achieving better machining performance compared to the conventional turning process. Moreover, a heating source has also been utilized to preheat workpiece material along with providing vibration to the cutting tool. Among various heat sources, the laser heat source is one of the most utilized heat sources due to its localized, rapid, and controlled heating at the workpiece surface. Hence, in the present study, a laser is used to preheat the workpiece material and ultrasonic vibration is provided to the cutting tool, and the developed hybrid turning process is termed as ultrasonic-vibration-laser assisted turning process. An experimental setup was developed to mount the transducer and laser head on the lathe machine so that vibration could be applied in the tangential, feed and radial directions, and it was synchronized for effective movement in the cutting direction. A tungsten carbide cutting tool was used to machine the aluminium 3003 alloy and magnesium AZ31B alloy workpiece material. Aluminium and magnesium alloys possess low melting temperature and high strength-to-weight ratio, and they are most commonly utilized in aviation, automobile, marine, biomedical, and electronics industries. Cutting speed and laser power were varied whereas all other parameters were kept constant during the experiments. Machinability analysis in terms of machining forces, machining temperature, tool wear, chip morphology and surface roughness, and surface integrity analysis in terms of surface damage, microstructure, microhardness, residual stresses and corrosion behavior was investigated for both alloys during the ultrasonic-vibration-laser assisted turning process. Lower machining forces, higher machining temperature, lower tool wear, smooth chip edges, lesser chip segmentation, lower surface roughness, lesser surface damage, higher grain refinement, higher microhardness, higher compressive residual stresses, and higher corrosion resistance were obtained for both alloys during the ultrasonic-vibrationlaser assisted turning process in comparison to the conventional, ultrasonic-vibration, and laser assisted turning processes. Furthermore, higher compressed air pressure was also utilized to suppress the higher machining temperature and higher tool wear during the machining of aluminium 3003 alloys. Lower machining forces, lower machining temperature, lower tool wear, lesser chip segmentation, and lower surface roughness were observed during higher compressed air pressure compared to the lower compressed air pressure. Therefore, the ultrasonic-vibration-laser assisted turning process is found to be more effective to improve the machinability and surface integrity of aluminium and magnesium alloys than other processes. The developed process can be applied to other machining processes and workpiece materials for improvement in machining performance.