The effect of surface condition on fatigue strength, corrosion fatigue prevention and the corrosion fatigue damage which occurred in the specimen were investigated in fresh water and aqueous solution containing sodium nitrite inhibitor at 80°C using relatively large Cr-Mo cast steel specimens.
A finely machined specimen (surface roughness, R<2s), a roughly machined specimen (R≅20s) and a shot blusted cast skin specimen had a clear fatigue limit in air. The fatigue limit of the roughly machined specimen fell to about 90% of that of the finely machined specimen, but the fatigue limit of the shot blusted cast skin specimen became very high compared with those of the finely and the roughly machined specimens. The fatigue strengths of the finely and the roughly machined specimens in fresh water at 80°C were the same level. Many corrosion pits and microcracks occurred on both the finely and the roughly machined specimens. The shape of microcracks was semielliptical when the stress amplitude was relatively high, but the microcracks were combined with each other and were stretched along the surface of the specimen when the stress amplitude was low. The fatigue strengths of the finely and the roughly machined specimens in aqueous solution containing. sodium nitrite inhibitor at 80°C had the same level of fatigue limit as those in air, and corrosion pits and microcracks were not observed. On the other hand, the behavior of the fatigue strength of the shot blusted cast skin specimen in fresh water and aqueous solution containing sodium nitrite inhibitor at 80°C was different from that of the machined specimens.
