Hydrogen is an integral part of the European Green Deal to achieve carbon neutrality in 2050. As part of the Deal, hydrogen internal combustion engines are qualified as zero emission vehicles. Such engines are favorable for all high-power applications, especially robust off-highway vehicles, and large trucks. However, the products (valves, valve seat inserts, sealings, pistons, rings, and liners) and materials used for such engines must first be subjected to a reliable hydrogen damage risk analysis.

Tenneco’s PACE award winning DuraForm-G91 premium aluminum piston material combines excellent mechanical properties at high temperatures and eminent manufacturability, forming the basis for a cost-effective use in hydrogen engines. The DuraForm-G91 alloy was investigated in the high-temperature testing regime up to 400 °C. To achieve this, the samples were charged in an autoclave at various temperatures and compared against oven-soaked material. Hydrogen content measurements, microstructural assessments, tensile and fatigue tests up to 400 °C, and differential scanning calorimetry were conducted on the different conditions. In addition, a specially at the BOKU University developed ultrasonic fatigue tester was used, which can operate at 250 °C in air, in pressurized hydrogen, or in nitrogen atmospheres at 35 bar. Finally, the outcomes were compared with material results after running in hydrogen engines.

The results clearly indicate that DuraForm-G91 is not negatively affected by hydrogen exposure. This conclusion comes from observing that hydrogen content levels remain low and all mechanical properties equal or exceed the reference outcomes. An explanation for these very positive results can be given using the differential scanning calorimetry measurements, which reveal a phase change in the material.