2011 年 60 巻 11 号 p. 1023-1030
This paper discusses the corrosion fatigue property of a high-strength cold-rolled eutectoid steel in deionized water to investigate the countermeasures against corrosion fatigue. The effects of temperature, stress cycle frequency and dissolved oxygen concentration on the corrosion fatigue strength in deionized water were investigated. In the case of smooth sample, lower stress cycle frequency, higher temperature and higher dissolved oxygen concentration decreased the fatigue strength in deionized water compared with that in dry air. Note that the corrosion fatigue strength decreased in the deionized water with a dissolved oxygen concentration of even 0.05ppm. The morphology of corrosion pit depended on the specimen orientation relating with a rolled pearlitic microstructure. Moreover, the addition of inhibitor increased the corrosion fatigue strength up to that in dry air because of the surface corrosion protection. It is more effective countermeasures for corrosion protection to add the inhibitor than to decrease the dissolved oxygen. However, even in ion-exchanged water with inhibitor, the fatigue strength of a sample having an artificial crevice was decreased compared with that of sample without the crevice. The corrosion pit formed inside of the crevice caused a decrease in fatigue strength. These results suggest that the corrosion protection effect becomes insufficient inside the crevice because the nitrous ion depleted due to the interruption of diffusion and convection.