Desgaste por fricção oscilatória do aço ASTM 52100 lubrificado com diesel fóssil e biodieseis de diferentes matérias primas e suas blendas

Abstract

The present work aims to evaluate the wear of ASTM 52100 steel (bearing steel) under oscillatory friction in the presence of different biodiesels and their blends. Biodiesels were obtained from soybean oil, coconut oil, canola oil, and pork lard, which were compared to pure diesel without additives and to fossil diesels (S500 and S10) commercialized in Brazil. After the characterization of the biofuels, cyclic (oscillatory) friction wear tests were carried out on the HFRR (High Frequency Reciprocating Rig) equipment, following ASTM G133 and D6079 standards. As a result of the tests, dynamic friction coefficients and characteristic wear tracks were obtained, which were measured to determine the worn volumes, wear rates, and analyzed by scanning electron microscopy and Raman spectroscopy to identify the wear mechanisms and surface interaction between the substrate and biodiesels. The worst performance was observed for pure diesel, with an average friction coefficient of 0.14599, which was 79% higher than the pork lard biodiesel, which showed the best performance with a friction coefficient of 0.081161. Regarding the wear rate, pure diesel also showed the worst result, losing almost 10 times more material than soybean biodiesel, which had the lowest wear rate. These behaviors were attributed to the low sulfur content, lack of lubricity additives, and high oxide formation in pure diesel (non-commercial), while for pork lard and soybean biodiesels, the formation of lubricating films on metal surfaces was associated with the presence of long-chain fatty acids. The use of Raman spectroscopy was essential to corroborate the mechanisms of protective layer formation in biodiesels, confirming their superior effectiveness compared to fossil diesel.