Effect of astaxanthin concentration on the wear properties of castor oil and wear rate prediction using non-linear regression by pin-on-disk tests

Numerous studies have aimed to identify biodegradable oils and additives as alternatives to mineral substances in industrial settings. Among these, castor oil combined with astaxanthin, a natural antioxidant, has demonstrated exceptional results compared to other substances. Consequently, this study examined the tribological performance of five mixtures of castor oil with different astaxanthin concentrations using sliding friction tests in a pin-on-disk tribometer based on the ASTM G99-23. For this purpose, steel disks of AISI 4140 and spheres of tungsten carbide (WC) with a diameter of 3 mm were used as counterparts. Each essay was performed by immersing the test specimens in the lubricant, controlling the temperature at 100 °C. The key finding is that the reduction in wear rate is directly affected by increasing astaxanthin concentration, which was observed in the wear mechanism. The correlation between wear rate and astaxanthin concentration was studied through a mathematical equation that estimates the value of the wear parameter at antioxidant concentrations beyond those tested experimentally. This achievement marks a significant milestone in applying statistics to complex systems, establishing a mathematical link between astaxanthin concentrations and wear properties.