Rotating bending fatigue tests were carried out for 18% Ni maraging steel in order to investigate the influence of reversion austenite on notch sensitivity of maraging steel. Fatigue strength was increased by formation of reversion austenite. The increase in the fatigue strength was large near the fatigue limit. In the range of notch radius ρ larger than 0.05 mm, fatigue limit was determined by the limit for crack initiation in the material without reversion austenite, whereas a non-propagating crack was observed in only the notched specimen of ρ=0.05 mm in the material formed reversion austenite. These were caused by suppressions of the crack initiation and its early propagation due to formation of reversion austenite. However, the influence of reversion austenite on notch sensitivity was very small.
