The role of synthetic oils in controlling hydrogen permeation of rolling/sliding contacts.

Bearing steels suffer from degradation of mechanical properties when atomic hydrogen diffuses into the steel from the contact surface. In rolling contact fatigue tests this can lead to a significant reduction in fatigue life of the specimens as the amount of hydrogen diffused into the steel increases. To mitigate this challenge, synthetic oils of different chemistry have been studied so as to identify their efficiency and mechanism of retarding or preventing hydrogen permeation.

Hydrocarbon Lubricants Can Control Hydrogen Embrittlement.

While it is well known that during RCF tests the formation of nascent catalytic sites on the wear track can break down hydrocarbon molecules to release atomic hydrogen, the potential of the hydrogen environment in fuel cells to hydrocrack the hydrocarbon lubricant in high pressure rolling contacts has so far been ignored. Here we investigate for the first time the ability of the hydrogen environment to generate a chemical tribofilm on the wear track most likely through lubricant hydrocracking, as compared with argon and air environments. Despite the ability of the hydrogen environment to generate a notably larger amount of atomic hydrogen, the chemical tribofilm significantly prevents the formation of atomic hydrogen and its subsequent diffusion through the lattice of steel rolling element bearings.

Self-lubricating Al-WS composites for efficient and greener tribological parts.

Due to their mechanical and physical properties, aluminium alloys possess wide potential in the automotive industry, particularly in hot reciprocating applications such as pistons for diesel and petrol engines. WS particle-reinforced composites could bring further improvements by reducing friction and wear between moving parts. Reducing friction improves efficiency by lowering energy/fuel use, ultimately leading to lower greenhouse gas emissions, while antiwear properties can prolong component life.

Effects of Environmental Gas and Trace Water on the Friction of DLC Sliding with Metals.

This paper describes an experimental study on the friction of a-C:H diamond-like carbon (DLC) and ta-C DLC coatings in gas with different concentration of trace water. Pin-on-disk sliding experiments were conducted with DLC coated disks and aluminum pins in hydrogen, nitrogen, and argon. Trace oxygen was eliminated to less than 0.

Macroscale Superlubricity of Multilayer Polyethylenimine/Graphene Oxide Coatings in Different Gas Environments.

Friction and wear decrease the efficiency and lifetimes of mechanical devices. Solving this problem will potentially lead to a significant reduction in global energy consumption. We show that multilayer polyethylenimine/graphene oxide thin films, prepared via a highly scalable layer-by-layer (LbL) deposition technique, can be used as solid lubricants.

Interferometry study of aqueous lubrication on the surface of polyelectrolyte brush.

The water lubrication behavior of a polyelectrolyte brush was investigated by using double-spacer-layer ultra-thin-film interferometry to determine the thickness of the aqueous lubrication layer present at the interface between the brush and a spherical glass lens. A hydrophilic poly{[2-(methacryloyloxy)ethyl]trimethylammonium chloride} brush was prepared on an optical glass disk coated with layers of semireflective chromium and silica. The thickness of the hydrodynamic lubrication layer was estimated interferometrically.