To clarify the effect of hydrogen gas environment on fatigue strength is important to design and to safely operate hydrogen utilization machines. In this study, fretting fatigue test in hydrogen gas environment was done. Test material was aluminum alloy T6061-T6. In case of relatively low contact pressure, fretting fatigue limit decreased in the order of air, nitrogen gas and hydrogen gas. Tangential force excerted on a pair of contact surfaces increased in the reverse order. Therefore, the difference of fretting fatigue strength was considered to be caused by the difference of tangential force among environments.
