The fatigue tests were conducted for high-strength steels, HT50 and HT80, in laboratory air, in ion exchanged water and in synthetic seawater, systematically. Three types of the notched specimens were used: shaft specimens with a groove, with a transverse hole and with a shoulder fillet. The results obtained were as follows:
(1) Synthetic seawater reduced the fatigue strength considerably. However, the strength in the synthetic seawater decreased slightly with an increase of αk (stress concentration factor) in comparison with that in laboratory air or in ion exchanged water.
(2) A notch reduced the fatigue strength remarkably in laboratory air and in ion exchanged water in the order of the specimens with a hole, with a shoulder fillet and with a groove, and HT80 was more sensitive to the notch than HT50.
(3) The increase of βk (fatigue notch factor) with increasing αk was smaller in synthetic seawater than that in laboratory air, but it was much larger than that in ion exchanged water.
