The Influence of Polymeric Ester-Type Additives on the Performance of Metal Cutting Fluids for Machining of Titanium Alloy

The introduction of additives to metal working fluid (MWF) compositions helps to reduce friction and wear while holding the possibility of sustainability to the environment. This study was performed to examine polymeric ester additives' influence on the MWFs performance during the drilling of a titanium alloy, Ti-6Al-4V, under a constant removal rate (MRR) of 4.2 mm³/s. The specific cutting energy (SCE) and build-up edge (BUE) were evaluated to assess the additives' performance in the MWFs. It was observed that the drilling performance of the polymeric ester additives was dependent on the drilling conditions employed. The high polarity polyester additive with high molecular weight displayed enhanced drilling performance under the drilling conditions with cutting speeds of 0.105, 0.188, and 0.293 m/s, and respective feed rates of 0.040 mm/r, 0.022 mm/r, and 0.014 mm/r. This enhanced drilling condition was reflected in the SCE with the high polarity polyester additive possessing lower values than the low-molecular-weight polymeric ester by 32, 27, and 35%, and the high-molecular-weight polymer ester by 17, 6, and 18% at each of the respective drilling conditions. The high-molecular-weight polymer ester was a more suitable additive under the drilling condition with a cutting speed of 0.419 m/s and feed rate of 0.01 mm/r, boasting a 27 and 24% improvement in SCE compared with the high polarity polyester and low-molecular-weight polymeric ester, respectively. The polymeric ester additives' performance could be attributed to the formation of a carbon-rich boundary layer on the cutting blade and the presence of oxygen and carbon in the BUE on the cutting edges.