Wear mechanisms and material deposition of high-performance polymer composites for hydrogen compression

•PTFE and carbon fibre improved piston ring composite materials show improved tribological behaviour in the piston ring tribocontact in the hydrogen compressor application.•Wear mechanism of the tribosystem was investigated in detail using FIB, TEM and EDX to analyse distribution of elements in a depth profile.•Wear mechanism changes to less wear with increased material deposition, in the investigated material pairings (steel vs high strength polymer composites).•Deposition can be optimized by adding PTFE into the polymer composite. The transistion to renewable energy production is a main component in achieving the climate targets defined in the 2015 Paris Agreement. Power-to-gas concepts, where electrical energy is stored as hydrogen gas, require the design and operation of state-of-the-art reciprocating compressor technology to realize high pressure ratios and high volumetric flow rates for gas supply demands. The main challenges in designing machines suited for these operating conditions are high thermo-mechanical stresses acting on the piston sealing rings. High shear loads and minimal ring gap sizes demand material pairings with excellent wear resistance and sliding properties. This work investigates the life cycle limiting wear mechanisms present in the piston compressor and develops advanced concepts for piston rings in cylinder tribo-contacts. PI and PPS polymers reinforced with carbon fiber were modified with dry lubricating PTFE to fulfil the requirements of this highly stressed tribo-system. Tribo-tests were performed against steel countersurfaces with a linear oscillating tribometer in pin-on-plate configuration. The failure mechanisms were analysed utilizing scanning electron microscopy on cross-sections cut into the depth of the countersurface material with focused ion beam milling. 2D scanning transmission electron microscopy mapping supported by energy dispersive X-ray spectroscopy were performed to analyze the depth profile of the deposited tribo-layer elements on the wear track.