定電位SSRT法によるSUS316鋼単結晶の応力腐食割れ

抄録

The stress corrosion cracking (SCC) of SUS316 steel single crystal was investigated with the potentiostatic slow strain rate technique. The smoothed specimens oriented for [001], [101], [111] and 0.50 in Schmid factor were prepared, and the susceptibility of each specimen to SCC was evaluated from the nominal stress-strain curve in a boiling 42% MgCl₂ solution at 416K.
The results indicated that the SCC under the open circuit condition occurred at the strain rate of 2.38×10^-5S^-1 and below, and the tensile strength and the elongation decreased with decreasing strain rate. The potential range for SCC appeared above -400mV vs. SCE which was nearly the critical potential for cracking. The uneven general corrosion occurred when the potential was shifted to more noble values. The susceptibility index to SCC defined by comparing with the nominal stress-strain curve in noncorrosive oil was almost constant in all single crystals. Thus, the resulting susceptibility was less dependent on the tensile axis orientation in comparison with the constant loading-tests. The fracture surface with coalescent steps was formed by the crack growth along ‹211› direction on {210} plane, regardless of test conditions.