Effect of the enriched vegetable-based oil as a metalworking fluid for machining applications / Zubaidah Binti Zamri

Faculty of Manufacturing and Mechatronic Engineering Technology

Thesis (Master of Science) -- Universiti Malaysia Pahang – 2025

Includes bibliographical references

Due to their eco-friendly and renewable characteristics, bio-lubricants are gaining interest in the current market as a novel substitute for conventional lubricants. The decrement in raw materials for the lubricant manufacturing process has forced researchers to look for new sources of lubricant production. Using petroleum oil as the base for lubricants has caused several issues such as depletion of mineral resources, increased oil extraction costs, and waste oil disposal after lubricant application. Furthermore, the procedure for disposing of oil waste is very complicated and requires expert personnel. As a result, some business owners improperly dispose the waste oil, which can pollute the soil, and water, as well as bring harmful damage to the marine life. Additionally, the high levels of toxicity in petroleum-based lubricants during machining operation can cause a high risk to the health of machine operators. Petroleum-based lubricants also have lower thermal and oxidation stability compared to bio-lubricants. However, bio-lubricants have several drawbacks due to the percentage of unsaturated fatty acids in them. In this regard, several modification methods need to be implemented to improve the properties of bio-lubricants such as lubricants and machining fluids. To enhance the efficiency of lubricants when used in high-temperature surroundings, additives need to be mixed into the bio-lubricant. In this study, chemically modified Tamanu oil with trimethylolpropane (MTO) was mixed with activated carbon as additives to formulate a bio-based metal-working fluid with solid additives. This activated carbon was added into the oil with varied concentrations of 0.01wt.%, 0.025wt.%, and 0.05wt.%. These mixtures are validated for their tribological performances using a four-ball wear test (ASTM D4172) and minimum quantity lubrication (MQL) with orthogonal machining operation on the AISI 1045 workpiece. Several physicochemical tests such as viscosity, density, viscosity index, flash point, and corrosion test were conducted to test the lubricant's properties. Results from the four-ball wear test and physicochemical properties of the lubricant showed that the lubrication performance of MTO and MTO with additives outperformed the synthetic ester sample used as the benchmark oil. Adding 0.01 wt.% of nano-activated carbon (NAC) to MTO results in the highest viscosity index (208.483) while MTO with 0.025wt.% NAC has outperformed other lubricants sample in the four-ball wear test result. MTO+0.025wt.% has the lowest coefficient of friction (COF) and demonstrates minimal ball groove formation. For orthogonal cutting data, the bio-based lubricants are on par with the synthetic ester in terms of its cutting force, feed force, cutting temperature, and chip formation. In terms of cutting fluid and cutting temperature data, MTO+0.01wt.% NAC has shown the lowest value, while SE shows the lowest feed force. In chip formation data, SE shows a bigger curvature radius compared to other metalworking fluids (MWFs). In conclusion, based on the data obtained from this study, MTO+0.01wt.% NAC has successfully outperformed the synthetic lubricant (SE) in terms of tribological performance observed after the tribological tests were conducted, in terms of oil viscosity, oil stability, and has successfully reduced temperature and force during the machining tests.MTO+0.01wt.% NAC can be a substitute for SE fluid towards greener machining practices.