Lanthanum Effect on the Tribological Behaviors of Natural Serpentine as Lubricant Additive

Abstract

The tribological properties of serpentine powders (Mg₆Si₄O₁₀(OH)₈, marked as FGM1) and the admixture of 95 wt% serpentine powders + 5 wt% La₂O₃ nanoparticles (FGM2) as oil additives were comparatively investigated using an optimal SRV-IV friction and wear tester. The worn surface was characterized by scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS) and X-ray photoelectron spectrometry (XPS) and the friction mechanism is discussed. The results show that both FGM1 and FGM2 had excellent tribological performance and 0.5 wt% content was the most efficient in reducing friction and wear at 50 N. With the addition of La₂O₃ nanoparticles, the tribological properties were further improved compared to those of serpentine powders alone. A smoother and more compact tribofilm with iron oxides, silicon oxides, graphite, organic compounds, and La_9.33 (SiO₄)₆O₂ was formed on the worn surface and provided further reduced friction and wear.

KEY WORDS:

• Antiwear Additives
• Friction Modifiers
• Boundary Lubrication
• Friction Mechanisms

ACKNOWLEDGEMENTS

We thank Professor Xia Yanqiu, Dr. Wang Yunxia, and Dr. Wang Bo for assistance with the tribological tests and XPS analysis. We also acknowledge financial support from the NSFC of China (No. 51205183), JSNSFC (No. BK2012475), and NJIT innovation fund (No. YKJ201204).

Review led by Tom Karis