The stress corrosion cracking (SCC) of an At ST C-1018 mild steel was investigated in three solutions, composed of 12.5 mol/kg NaOH, 3.35 mol/kg NaOH and 2.5 mol/kg NaOH + 0.42 mol/kg Na₂S, respectively. The potential of maximum susceptibility to SCC of steel in the latter two solutions was assessed by a slow strain rate technique. It was found to be slightly higher than the active-passive transition in each solution (-1.00 Vsce in 3.35 mol/kg NaOH and -0.88 Vsce in 2.5 mol/kg NaOH + 0.42 mol/kg Na₂S).
A fracture mechanics technique, utilizing fatigue
precracked double cantilever beam specimens, was then
used to study the effects of stress intensity, temperature
and electrochemical potential on crack velocity in all
three solutions. Both stress intensity dependent (region
I) and stress intensity independent (region II) crack
velocity behavior was found. Apparent activation energies
for region II of ~ 24 kJ/mol were determined at both
Ecorr and -1.00 Vsce in 12.5 mol/kg NaOH. Crack velocities
of the order of 10⁻⁹ m/s were measured at Ecorr in
12.5 mol/kg NaOH and at -1.00 Vsce and -0.88 Vsce 3.35 mol/kg NaOH and 2.5 mol/kg NaOH + 0.42 mol/kg Na₂S,
respectively. The crack velocities measured at -1.00 Vsce
in 12.5 mol/kg NaOH were of the order of 10⁻⁸ m/s. The fractography of the cracks was transgranular in 12.5 mol/kg NaOH at Ecorr. A mixed intergranular-transgranular fractography was observed at the active-passive transition in all three solutions.
The results of the two techniques were compared and discussed, as was the role of stress intensity and passivation rate in fracture mechanics experiments. Anodic dissolution, hydrogen embrittlement and adsorption mechanisms
were considered. It was decided that the results at Ecorr
in 12.5 mol/kg NaOH could best be accounted for by a hydrogen embrittlement mechanism, perhaps assisted by anodic dissolution. Hydrogen embrittlement was eliminated as a possible mechanism at the active-passive transition in all the solutions. The most likely mechanism was thought to be one involving mixed activation-diffusion controlled dissolution. Applications of the results to the pulp and paper industry were considered. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/22545 |
| Date | January 1981 |
| Creators | Singbeil, Douglas Lloyd |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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