Numerical Modelling of Machining of Titanium Alloys Under Phosphonium-Based Halogen-Free Ionic Liquid as Lubricant Additives

In general, dry machining of titanium alloys leads to poor surface finish of the machined product. Also, the tool life is low specifically when machining difficult-to-cut materials. Therefore, lubricants are used, however, traditional lubrication with flood cooling has various detrimental environmental effects as well as it costs approximately 17% of the total cost of the product. As a result of the aforementioned factors, it is essential to employ bio-based lubricants with minimum quantity lubrication (MQL) in the machining process to make the process environmentally friendly and economical. However, bio-based lubricants such as vegetable oils have low pour points and are susceptible to oxidation as well as degradation. To improve the properties of vegetable oils, ionic liquids (ILs) have emerged as desirable additives for metalworking fluids owing to their unique qualities such as low or minimal volatility, strong polarity, and excellent thermal stability. However, most of the ILs being used as lubricant additives are halogen-based. Halogen-based ILs are sensitive to moisture and have the potential to produce dangerous halogen acids, which can corrode metal surfaces. In this work, numerical analysis using ABAQUS™ was performed to investigate the effect of mineral oil and canola oil blended with halogen-free ILs under MQL environment on cutting temperature and cutting forces. For comparison, simulations were also carried out under dry machining. Simulations were performed at two different cutting speeds (80 and 120 m/min) at a constant feed of 0.1 mm. Results show that the cutting temperature was reduced by 13.75 and 9.98% under canola oil blended with halogen-free ILs at 80 m/min and 120 m/min, respectively as compared to dry conditions. Also, cutting forces were reduced by 14–15% under canola oil blended with halogen-free ILs under the same conditions. Whereas, mineral oil used with MQL shows the total reduction of cutting temperature by 8.8 and 4.4% and cutting forces by 8.77% and 8.69% at 80 m/min and 120 m/min, respectively as compared to dry machining. This is attributed to the adsorption of ILs on the metal surface, which formed the lubrication film and reduces the friction resulting in lower cutting temperature and cutting force.