Hydrocarbon Lubricants Can Control Hydrogen Embrittlement

Abstract

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. this is of great importance in the lubrication of hydrogen technology and the prevention of Hydrogen embrittlement (He). An investigation into the prospects of high energy micro-computedtomography (Micro-ct) as a non-destructive technique for sub-surface damage characterisation in Rcf was comparatively performed alongside traditional sectioning methods.

Hydrogen Impermeable Materials for Efficient Hydrogen Storage

“…Lubricants, on the other hand, can have a key part in reducing damage to steel elements that have undergone lubrication through hydrogen atoms and therefore extending the operational life of materials when they are properly manufactured or utilized in appropriate operating parameters. As they are able to produce a protective layer on the wear track, they can prevent HE by suppressing hydrogen atom generation on the nascent steel substrate and functioning as a hydrogen penetration barrier (HPB) (20).…”

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

“…24 Despite hydrocarbon lubricants have been denounced as one of the main sources of atomic hydrogen, recent studies of RCF tests lubricated with PAO in air, hydrogen and argon atmospheres proved that air and hydrogen gas can enable the formation of tribolms on the wear track and reduce the hydrogen content in steel. 18,25 The tribolm consisted of mainly solidied hydrocracked or oxy-polymerized carbon species and iron as oxides and elemental forms possibly generated through oil oxypolymerization (in air) and hydrocracking (in hydrogen) and its thickness decreased in the order Air > H 2 > Ar. 25 The chemistry of the hydrocarbon oils determines their physico-chemical properties such as polarity, water and air solubility, oxidation, thermal and hydrolytic stability etc.…”

“…18,25 The tribolm consisted of mainly solidied hydrocracked or oxy-polymerized carbon species and iron as oxides and elemental forms possibly generated through oil oxypolymerization (in air) and hydrocracking (in hydrogen) and its thickness decreased in the order Air > H 2 > Ar. 25 The chemistry of the hydrocarbon oils determines their physico-chemical properties such as polarity, water and air solubility, oxidation, thermal and hydrolytic stability etc. These characteristics are important not just to ensure efficient lubrication but also for their ability to generate tribolms on the wear track through processes such as oxypolymerization and hydrocracking.…”

“… 18,25 The tribofilm consisted of mainly solidified hydrocracked or oxy-polymerized carbon species and iron as oxides and elemental forms possibly generated through oil oxypolymerization (in air) and hydrocracking (in hydrogen) and its thickness decreased in the order Air > H 2 > Ar. 25 …”

“…These characteristics are important not just to ensure efficient lubrication but also for their ability to generate tribofilms on the wear track through processes such as oxypolymerization and hydrocracking. 25 This study aims to ascertain how the base oil chemistry influences lubrication performance, tribofilm characteristics and the changes in oil condition during testing in air. Thrust bearing type tests were conducted in air for up to ten hours using three types of synthetic oils selected to have similar viscosity but different chemistry.…”