Mechanism of reduction of fretting fatigue limit caused by hydrogen gas in SUS304 austenitic stainless steel

The fretting fatigue strength of pre-strained SUS304 is reduced in hydrogen gas. The mechanism of the reduction is discussed. In hydrogen gas, local adhesion between contacting surfaces occurred and many small cracks were formed at the adhered spots. The major crack propagated from one of the small cracks. The roles of the adhesion in relation to the initiation and propagation of the small cracks were examined by a two-step environment test. When adhesion was prevented by an oxidized film, no failure of the specimen occurred. It can be presumed that the stress conditions were more severe in hydrogen gas than that in air due to local adhesion.

Research highlights
► Fretting fatigue strength of SUS304 was significantly reduced in hydrogen gas.
► The role of hydrogen gas to reduce fretting fatigue strength of SUS304 was examined.
► Adhesion was dominant in the process causing the fretting wear damage in the hydrogen gas.
► Many small cracks emanated from the adhered spot.
► The reduction was caused by adhesion, small cracks and increase in the tangential force.