Tribological Behavior of Calcium Complex Palm-Biogrease with Green Additives

Vegetable oils have been acknowledged to have significant potential as a substitute base fluid in grease formulation. The so-called biogreases are demanded especially in open applications where the greases are in contact with soil and water and lost to the environment. In this paper, formulation of a biogrease derived from palm-based ester as the base fluid and calcium complex soap as the thickener is discussed, with the main purpose to explore the potential of palm oil as an effective biodegradable fluid, and to investigate the possibility to improve the tribological properties by mixing calcium carbonate (CaCO3) and hydroxyapatite (HA) as green additives. The wear and friction properties as well as the load carrying capacity of the formulated bio-grease were extensively studied through the four-ball wear tester. The experimental results show that the average coefficient of friction of the palm based biogrease was improved by about 6.5% when 5% of CaCO3 and 3% of HA were added comparing to base grease. Besides, the load carrying capacity was also enhanced significantly by the addition of the additives. This demonstrated the good potential of palm ester as base fluid for grease and the CaCO3 and HA as lubricant additives, exhibited the good anti-friction and load carrying abilities.