Investigating Corrosion and Surface Hardness of Al6061 in Machining Fluids with Variable CNT Concentrations

Abstract

This project investigates the corrosion tendency of various machining fluids on Al6061 alloy for a sustainable cutting process. Also, the surface of the machining workpiece was analysed to understand the effect of the carbon nanotubes (CNTs) on the surface morphology that assists the cutting conversion of the sliding friction to the rolling process. The study used a two-step process to create machining fluid with CNT nanoparticles at different percentage concentrations. The soluble oil (sample B1), mineral oil (sample B2), 0.2-g/l-CNTs nano-mineral machining fluid (sample B3), 0.4-g/l-CNTs nano-mineral machining fluid (sample B4), and 0.6-g/l-CNTs nano-mineral machining fluid (sample 5) makes up the corrosion study medium. The corrosion study was conducted using polarisation resistance and potentiodynamic corrosion techniques. After the corrosion study, the Vickers micro-hardness machine was employed to evaluate the surface hardness of the normal face region subjected to the corrosion study. The SEM and EDS were also used to investigate the microstructure and elemental composition of the machining fluid impacts on the Al 6061 alloy. The results show that the soluble oil has a high corrosion rate of 0.03590591 (mm/year), with a list polarisation resistance rate of 8,432.83 (Ω) compared to the other machining fluid employed in this study. Furthermore, the 0.6-g/l-CNTs nano-mineral machining fluid has the lowest corrosion rate of 0.0013197 (mm/year) and the highest polarisation resistance of 32,941.67 (Ω). The 0.6-g/l-CNTs presence in the mineral oil increases the rheological and tribological properties, which results in an outstanding performance in the corrosion study. Furthermore, the CNTs hardened the surface of the workpiece due to the carbon element deposition during the implementation of the cutting fluid.