The tribological behaviour of various engine components can be impacted by alternative fuels, such as hydrogen. It is imperative to undertake a comprehensive evaluation of the various tribosystems, with a particular focus on the ring-on-liner contact. The impact of hydrogen on the tribosystem is multifaceted, manifesting in phenomena such as hydrogen embrittlement, alterations to tribochemical reactions, and modifications to oil properties and additives. The objective of this study was to comprehend the impact of hydrogen on the scuffing behaviour of the tribosystem, specifically examining the interaction between a CrN piston ring and a cast-iron cylinder. A novel methodology was developed to create a localised hydrogen atmosphere through the spraying of hydrogen onto the contact, while the ring and liner specimens were pre-loaded and the oil was continuously flushed with hydrogen. The materials of the tribosystem demonstrated a high level of resistance to hydrogen embrittlement but were affected otherwise by hydrogen, as evidenced by the marginally lower scuffing limit during testing with hydrogen. The underlying reason is attributable to the effect of hydrogen on three factors: the formation of tribofilms, the reduction of oxide layers, and changes in oil properties. • Tribotesting with a localized hydrogen atmosphere • Fast diffusion of hydrogen under elevated temperatures • High hydrogen embrittlement resistance of cast iron liners and PVD rings • Reduction of the scuffing limit in the ring-on-liner contact under hydrogen
Breitegger et al. (Wed,) studied this question.