Instrumentação de um tribômetro com espectroscopia Raman para avaliação in situ da formação de filme lubrificante

Abstract

With the industry's modernization, the demand for more sustainable lubricants has grown exponentially worldwide due to their renewable and biodegradable aspects. Lubricants' properties are conferred through their additives; however, most of these additives are compounds based on sulfur and other toxic compounds to the environment. In this context, the use of nanoparticles as an alternative additive has gained space and proved to be very efficient; however, wear reduction in nanoadditivated bio-lubricants occurs through mechanisms that need to be explained, which leads to the need for adequate characterization techniques for this. Raman spectroscopy is a technique that stands out in the characterization of tribomechanical systems due to the ease of obtaining data without preliminary sample preparation. This work aims to develop a low-cost Raman spectrometer and instrumentation in a pin-on-disk tribometer and a high-speed camera to characterize the formation of the lubricating film lubricated systems that act under relative motion. The tribological tests were carried out at boundary lubrication regime, with low speed, and at three loads, 100 N, 150N, and 200 N. Also, the Raman analysis was performed on the wear track during the tests every 10 minutes. The tribopar was made of SAE 1045 steel (Disc) and SAE 52100 steel (sphere). The lubricant used was pure epoxidized soybean oil and additive with polymeric amorphous carbon nanoparticles in concentrations of 0.05%, 0.1%, and 0.2%. After the tribological tests, the disc's wear track was evaluated by scanning electron microscopy, Raman spectroscopy, and profilometry. The results show that the developed Raman spectrometer is functional. For the concentration of 0.05%, friction coefficients characteristic of super low-friction were observed, improving lubrication and decreasing wear. For higher concentrations, nanoparticles intensify the abrasive effect due to interaction with the surface and agglomeration with secondary nanoparticles.