In pursuit of sustainability in machining titanium alloys using phosphonium-based halogen-free ionic liquids as potential metalworking fluid additives

Abstract

In recent years, researchers have investigated ionic liquids (ILs) as suitable metalworking fluids (MWFs) additive. Most commonly used ILs contain halogen anions, which creates issues related to corrosion and toxicity. However, phosphonium-based halogen-free ILs (HF-ILs) provide a safer alternate with enhanced biodegradability and minimal adverse effects on the environment. This research examines the potential of HF-ILs as an additive to canola oil. In this research two halogenated ILs [BMIM][PF6]- and [BMIM][BF4]- and one halogen-free IL ([P6,6,6,14][i(C8)2PO2]-) were added 1% by volume in canola oil. First, the thermophysical properties of these synthesized MWFs were evaluated. Result concluded that the HF-ILs reduced contact angles on both the workpiece and the cutting tool surfaces by 12- 15% compared to pure canola oil. Whereas, improved the thermal conductivity by 10.5%. Furthermore, the machining operation was carried out at two cutting speeds (80 and 100m/min) and feed (0.1 and 0.2mm/rev) to analyse the effect of synthesized MWFs under the minimum quantity lubrication method. Findings concluded that phosphonium-based halogen-free IL showed better cutting performance, with reduction in tool wear, cutting temperature by 10-33%, and surface roughness by 34−46%. Additionally, this approach supports a "greener" and more sustainable work environment by lowering MWF consumption by using minimal quantity lubrication, reducing tool wear and surface roughness which helps in cost reduction and product rejection for any manufacturing industry.