Estudo tribológico de óleos biodegradáveis de coco e de rícino através de ensaios abrasivos

Abstract

Oils can be of two different origins, biological and non-biological, and this provides a vast array of hydrocarbon compounds. These substances are usually present as complex mixtures and can be used for many other purposes besides lubrication, that is the control of wear and friction. Modern technology places severe and varied demands on lubricants, so the selection and formulation of appropriate mixtures of hydrocarbons for the purposes of lubrication is a skilled and complex process. Replacing mineral oils, biodegradable oils have been providing a great alternative to the industrial market, since it reduces environmental impacts. In order to evaluate the performance of ricin oil (crude and refined) coconut oil and comparing them with mineral oil SAE 20W50 SJ and W40, tribological wear tests were performed using the steel AISI 52100 pin-on-cylinder configuration. The surfaces of metallic samples were prepared by turning and sanding, using sandpaper of different grain sizes, followed by ultrasonic cleaning bath and weighing before and after the tests. The coupons (pins) used in evidence before the tests were analyzed in the optical microscope. The hardness of the AISI 52100 steel was measured using a Rockwell hardness test. The oils were characterized by testing the density and surface tension. The efficiency of action of the lubricant was evaluated through the calculated wear rates for the coupons using Archard's equation and by scanning electron microscopy (SEM). According to results of the wear rates, the vegetable oils such as castor oil and unrefined coconut obtained values of 88.89% and 66.67% lower than for the oils and SAE 20W50 SJ W40, respectively. Therefore, the vegetable oils have similar or superior tribological properties than for the studied mineral oils