Relationship among fatigue life, inclusion size and hydrogen concentration for high-strength steel in the VHCF regime

Based on experimental data and from the viewpoint of linear elastic fracture mechanics (LEFM), this paper proposes the relationship among fatigue life, Nf, nonmetallic inclusion size, r0, and hydrogen concentration in steel, CH, for high-strength steels in the very high cycle fatigue (VHCF) regime. Fatigue life, depending on the inclusion size and hydrogen concentration, decreases significantly with inclusion size and/or hydrogen concentration increasing. For the high-strength spring steel 60Si2CrV, if the inclusion size is reduced by one-third or one-half, the fatigue life will be up to about 10 or 100 times, respectively. Finally, the relationships of fatigue strength and fatigue life with inclusion size were compared.