Tribological characterization of vegetal lubricants: Comparative experimental investigation on Jatropha curcas L. oil, Rapeseed Methyl Ester oil, Hydrotreated Rapeseed oil

Biodegradability, good lubricating properties and low production costs, are the reasons to consider the plant oils a good alternative as reference to replace the petroleum-based oils that have limited resources. The based plant oils are very attractive as alternative lubricant source. Therefore, the aim of this work is to investigate on physicochemical and tribological performances of three plant seed based oils in the lubricating contact pair AISI E52100 steel sliding against X21OCr12 steel. Fatty Acid Methyl Ester (FAME), Hydrotreated Vegetable oil (HVO) from raw rapeseed oil and raw Jatropha curcas L. oil (JCL) were chosen. The oils were analysed for their chemical and physical properties such as viscosity, density flash point and TAN. The tribo-tests were carried out using ball-on-flat reciprocatory tribometer for several frequencies and normal loads. The oils exhibited good physicochemical properties and could be favourably used as lubricant feedstock in industrial application. The friction coefficient in all tests, for the HVO, stays in the range of 0.14-0.17, in the range of 0.11-0.14 for the Rapeseed Methyl Ester oil (RME) and in the range of 0.11-0.13 for the Jatropha curcas L. seed oil. JCL showed the lowest CoF among the three oils examined, followed by RME and HVO. Whereas, spheres lubricated with HVO underwent to the lowest wear but presented the highest roughness.