Analysis of thermal stability and lubrication characteristics of Millettia pinnata oil

Lubricants are mostly used to reduce the friction and wear between sliding and metal contact surfaces, allowing them to move smoothly over each other. Nowadays, due to the increase in oil prices and reduction of oil reserves, it is necessary to replace mineral oil, which will also protect the environment from hazards caused by these oils. It is essential to find an alternative oil for the replacement of mineral-oil-based lubricants, and vegetable oil already meets the necessary requirements. Vegetable-oil-based biolubricants are non-toxic, biodegradable, renewable and have a good lubricating performance compared to mineral-oil-based lubricants. This study analyzes the thermal stability and lubricating characteristics of different types of vegetable oil. The friction and wear characteristics of the oils were investigated using a four-ball tester, according to ASTM method 4172. Millettia pinnata oil has good oxidation stability due to the presence of higher percentages of oleic acid in its fatty acid composition. Millettia pinnata oil also shows a higher kinematic viscosity. Rice bran oil shows a higher viscosity index than other oils, and it is better for boundary lubrication. In thermogravimetric analysis, it was found that Millettia pinnata oil remains thermally stable at 391 °C. Millettia pinnata oil showed a lower coefficient of friction and rice bran oil showed a lower wear scar diameter compared to other vegetable oils and lube oils. A lower wear scar surface area was found with rice bran oil compared to other vegetable and commercial oils. Therefore, due to a better lubricating performance, Millettia pinnata oil has great potential to be used as a lubricating oil in industrial and automotive applications.