The growth characteristics of small surface cracks for high-strength steel in a corrosive environment. (2nd Report. Results in distilled water).

The growth characteristics of small cracks in distilled water were investigated for the high-strength steel SNCM439. The results were compared with the results obtained in a 1%NaCl solution. The fatigue and the stress corrosion cracking (SCC) behaviors of long cracks in distilled water were the same as those in the 1%NaCl solution. However, the growth rates of small fatigue cracks in the 1%NaCl solution were faster than the rates in distilled water. It was found from the SCC tests of small cracks in distilled water that KISCC decreased with decreasing crack length in the range of less than 0.6mm. At a crack length of more than 0.6mm, KISCC was equivalent to that of long cracks. In the 1%NaCl solution, KISCC decreased for the range of crack lengths of less than about 2mm. It was suggested that the difference in the results obtained from both environments was caused by the chlorine ion (C1-) contained in the 1%NaCl solution.