Tribological Response of Watermelon Seed Oil on AISI52100 and AISI 1045 Friction Pair

This study investigated the tribological responses of watermelon seed oil on steel contacting surfaces. Mineral oil as a major source of lubrication has, three major drawbacks: poor lubricity, non-biodegradability, and a high coefficient of friction. Hence, there is an urgent need for an environmentally friendly lubricant of which oils from plant sources such as vegetable seed oil can serve as an alternative source of lubrication. The choice of the watermelon seed oil is intended to address these drawbacks. Hence, this study presents a comprehensive way of not only determining the physicochemical characteristics of the vegetable oil but its tribological responses on steel contacting surfaces. Watermelon seed (Citrullus lanatus) oil was the vegetable oil investigated in this study. The friction and wear characteristics on both dry and lubricated conditions were examined using a tribometer (version 6.1.17). The coefficient of friction for the dry condition was observed to be in the range of 0.147 to 0.264, while for moderate (2 to 20) N lubricated condition was within 0.102 to 0.125, showing a drastic reduction in both friction and wear in the order: watermelon seed oil is greater than the mineral oil. Series of tests were performed to examine the physicochemical properties of the oils. The tests included viscosity test, density, pour point, etc. The reduction in friction and wear when lubricated with watermelon seed oil and its superior physicochemical properties suggests its potentials as a lubricant.