Lubricant/surface interactions under extreme pressure conditions: Corrosion inhibitor interacting extreme pressure/anti-wear additives on steel surface

Abstract

Many mechanical systems operate under mixed-boundary lubricated conditions. Moreover, these mechanical systems have highly loaded non-conformal contact surfaces, therefore significantly influencing friction/wear performance and also inducing various modes of failures. Hence, it is important to optimize selection of the lubricant since it plays a crucial role in controlling friction and affecting durability by forming tribochemical film on top of contact surfaces. The aim of the present work is to investigate the influence of extreme pressure additives, anti-wear additives, and corrosion inhibitors interacting at a steel/steel lubricated contact under extreme conditions and characterize the additive/surface interactions by advanced surface analysis techniques. The tribological testing was carried out employing a ball-on-disc test rig (ASTM G99-05) to measure friction. The wear on the balls was observed on the optical microscope after completion of the tribotest. Energy dispersive X-ray analysis and X-ray photoelectron spectroscopy were used to access the chemistry on the surface. In this paper, synergistic effects and antagonistic effects in terms of tribological parameters (friction and wear) are discussed, and mechanisms of the interactions are explained by surface analysis. Implications for optimizing the system performance are discussed.