抄録
The stress corrosion cracking (SCC) initiation behavior under a sustained load with small vibratory loads superimposed has been investigated on a high-strength low-alloy steel AISI 4135 sensitive to hydrogen embrittlement (HE) type SCC immersed in 3.5% NaCl solution at both the free corrosion potential and the cathodically charged potential at E=−1.0 V (SCE). At the free corrosion potential, the time to crack initiation with small vibratory stresses superimposed is shorter than that of static SCC with lower 600 ks strength than σSCC for static SCC. At Δσ≤74 MPa, however, the effects of superimposed stresses on 600 ks strength are negligible with the same value as σSCC. At σmax>σSCC, SCC cracks are initiated at the corrosion pits formed on specimen surfaces. At σmax<σSCC and Δσ>74 MPa, however, superimposed vibratory stresses promote stress-assisted crack-like dissolution preceded by corrosion pits; dynamic SCC cracks are initiated at the bottom of crack-like defects, resulting in the lower dynamic SCC strength. KISCC*, which is obtained by assuming the corrosion pits and the crack-like defects to be sharp cracks, is roughly equivalent to KISCC obtained by long, sharp crack specimens. When the cathodic potential is applied to specimens, the effects of superimposed small vibratory stresses on the 600 ks strength are negligible, because the metal dissolution reaction is inhibited. In such cases SCC cracks are initiated at the interior of specimens where the triaxial stress is maximum.
