Abstract
The growth characteristics of small fatigue cracks in 0.1N-NaOH solution have been investigated on a high-strength steel, SNCM439. The results obtained were discussed on the basis of the stress corrosion cracking (SCC) behaviour, and were compared with those in distilled water and in 1%NaCl solution already obtained in a previous study. Long cracks in 0.1N-NaOH solution grew faster than in room air atΔK >10 MPa√(m), and this behaviour was the same as the results in distil1ed water and in 1%NaCl solution. Small cracks also showed higher crack growth rates than those in room air atΔK >15 MPa√(m), which was larger than theΔK value for long cracks mentioned above. Although, in distilled water and in 1%NaCl solution, small cracks grew faster than in room air, theΔK values at which the crack growth rates were enhanced were much lower than that in 0.1N-Na, OH solution. These differences in the acceleration behaviour were found to be strongly related to the SCC behaviour, because the K1scc values increased with decreasing crack length in 0.1N-NaOH solution, while they decreased with decreasing crack length in distilled water and in 1%NaCl solution. Fractographic observations on SCC fracture surfaces revealed predominantly intergranular fractures, and there was no evidence of anodic dissolution on intergranular facets in a small crack region.
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