Tribological Properties of the Nanoscale Spherical Y2O3 Particles as Lubricant Additives in Automotive Application

Abstract

The continuous tribological development of engine lubricants is becoming more and more vital due to its fuel efficiency improvement and lifetime increasing potential. The antiwear additives play a high role in the lubricants to protect the contacting surfaces even in the presence of thinner oil film. Nanoscale spherical particles in the lubricant may increase the necessary protecting effect. This paper presents the results of the experimental tribological investigation of nanoscale spherical Y2O3 (yttria) ceramic particles as an engine lubricant additive. The ball-on-disc tribological measurements have revealed an optimum concentration at 0.5 wt% with about 45% wear scar diameter and 90% wear volume decrease, compared to the reference, neat Group III base oil. The high-magnitude SEM analysis revealed the working mechanisms of yttria: the particles collected in the roughness valleys resulted in a smoother contacting surface, they were tribo-sintered and they have also caused slight plastic deformation of the outer layer of the metallic surface.

Investigation of the Applicability of Y2O3–ZrO2 Spherical Nanoparticles as Tribological Lubricant Additives

“…It is necessary to compare the acquired results of the yttria-zirconia nanoparticle mixture with previous research results, in which these nanoparticles were separately tested with the same investigation method. The currently presented result tendencies correlate with both the zirconia results [28] and the yttria results [17], but the results of this mixture of nanoparticles are nearer to the zirconia results. In the case of neat yttria nanoparticles, there were concentrations (between 0.2 and 0.4 wt%) where the wear volume was increased compared to the reference, while the zirconia nanoparticles showed similar tendencies to the current yttria-zirconia mixture results; nevertheless, the neat zirconia particles were only investigated without Triton X-100 extra dispersant additive.…”

“…In the previous article of the authors [17], a surface-active dispersant additive was necessary for the yttria nanoparticles to avoid the formation of larger nanoparticle agglomerates. These larger agglomerates of nanoparticles could decrease the tribological performance of the oil by increasing the three-body abrasion wear on the contacting surfaces.…”

“…However, no research could be found about the synergy of the two ceramic additives. As yttria is a rare and expensive ceramic, a synergy should be sought in which it exerts its previously beneficial effects even at lower concentrations [17]. The weight ratio of yttria stabilizedzirconia (YSZ), which is very common in practice, was used to study the synergy.…”

“…To create a more homogeneous and stable mixture, 1% Triton X-100 (TX100) nonionic surfactant dispersant was added to the mixture (purchased from Reanal Laborvegyszer Kereskedelmi Ltd., Budapest, Hungary). In the previous research activities of the authors [17], neat yttria nanoparticles were investigated with the same methodology and the negative effects of yttria nanoparticles were only defined without the addition of extra nonionic surfactant dispersant by formulating agglomerates. According to this result, the yttria-zirconia mixture was only investigated with the addition of Triton X-100 dispersant.…”

“…Yttrium oxide (Y 2 O 3 , known as yttria) is a high hardness ceramic type material resembling zirconia in its properties that is also found in nature, although it is very rare. Yttria alone has not yet been studied as a nanoadditive, although previous research has shown a reduction in wear volume of up to 90% [17]. However, several studies reported that it has excellent results in tribology-related topics, especially wear-reducing and anti-corrosion effects as an additive in coatings and/or composites.…”