Characterization and Modeling of Nano Wear for Molybdenum-Based Lubrication Layer Systems

Abstract

As a result of global economic and environmental change, the demand for innovative, environmentally-friendly technologies is increasing. Employing solid lubricants in rolling contacts can reduce the use of environmentally harmful greases and oils. The aim of the current research was the development of a solid lubricant system with regenerative properties. The layer system consisted of a molybdenum (Mo) reservoir and a top layer of molybdenum trioxide (MoO3). After surface wear, Mo is supposed to react with atmospheric oxygen and form a new oxide. The determination of the wear volume of thin layers cannot be measured microscopically, which is why the wear behavior is initially determined on the nano level. In this work, single Mo and MoO3 coatings prepared by physical vapor deposition (PVD) are characterized by nano testing. The main objective was to determine the wear volume of the single coatings using a newly developed method considering the initial topology. For this purpose, nano-wear tests with different wear paths and normal forces were carried out and measured by in situ scanning probe microscopy (SPM). Based on the characteristic values determined, the coefficient of wear was determined for wear modeling according to Sarkar. The validation of the wear model developed was carried out by further wear tests on the respective mono layers.

Tribological Performance Evaluation of Greases on a Four-Ball Tester with Graphene Oxide Nanoparticles

“…As shown in Figure b, TEM images supported the existence of the nanotube structure, which has an average external diameter of 1–4 nm. A broad (almost sharp) characteristic peak at 2θ = 11.56 °C, corresponding to the basal plane (002) with about 54% crystallinity, is visible in the graphene’s XRD pattern, as shown in Figure c. , Due to the formation of a few layers of rGO following the reduction process, the broad peak denotes the phase of crystals that are randomly arranged. Additionally, the interlayer spacing- d (fwhm = 5.13) accounted for 0.35 nm in accordance with Bragg’s law, and the average grain size was calculated from Scherrer’s formula to be 1.67 nm, confirming the removal of functional groups containing oxygen during the process of manufacturing .…”

Friction and Wear in Nanoscratching of Single Crystals: Effect of Adhesion and Plasticity

“…Many of the conventional studies focus on friction and wear in specific material systems, e.g., the zirconia composites [ 52 ], the magnesium alloy [ 53 ], and the molybdenum-based systems [ 54 ]. However, due to the differences in material properties, a deep understanding of friction behavior remains ambiguous.…”

Insights into modeling approaches for boundary- and mixed-lubricated conditions

“…Another macroscopic approach, which tackles a new angle in the tribology of solid coatings, relates to the prediction of wear. Most recently, Behrens et al (2021) extended the Archard approach toward predicting wear volume. Scanning probe microscopy imaging of the worn surfaces having single Mo and MoO 3 coatings deposited by physical vapor deposition allowed for the measurement of wear volume and wear path subsequent testing during a movement cycle whereby wear is constant throughout the cycle.…”

“…The interpolation between varied test conditions gives the CoW for conditions of interest. Such interpolation was conducted with eight wear tests conducted at two varied load and number of passes (Behrens et al, 2021).…”

“…Figure5Theoretical and experimentally wear volumes for Mo and MoO 3 under the different combination of normal force (mN) and number of passes (P) from experiments and calculations from(Behrens et al, 2021) …”