Effect of oxygen addition on fretting fatigue strength in hydrogen of JIS SUS304 stainless steel

• The effect of oxygen addition on fretting fatigue strength in hydrogen is studied.
• Oxygen addition to hydrogen mitigated the fretting fatigue strength in hydrogen.
• Hydrogen participates to the crack nucleation at adhered spot.
• The crack initiation limit increased by oxygen addition to hydrogen.
• The adhesion between contacting surfaces is prevented by the oxygen addition.

Fretting fatigue test of SUS304 austenitic stainless steel was performed in air, in hydrogen gas, and in oxygen–hydrogen mixture. The fretting fatigue strength is more significantly reduced in hydrogen as compared to air. An increase in the fretting fatigue strength was found in the mixture. The mechanisms were investigated focusing on crack initiation. As the result, the crack initiation limit was significantly lower in hydrogen than in air, and increased in the mixture. The tangential force coefficient in the mixture is similar to that in air. The morphology of the fretting damage in the mixture was similar to that in air. These results indicated that the adhesion between contacting surfaces was prevented by addition of oxygen.