Low Temperature Stress Corrosion Cracking Research Articles

A probe into low-temperature stress corrosion cracking of 304L stainless steel by scanning vibrating electrode technique

Scanning vibrating electrode technique (SVET) that is a reliable method for local measuring of electrochemical potential at the sample surface is used to study stress corrosion cracking of 304L stainless steel in 0.1 M NaCl+HCl solution at room temperature. SVET maps showed a periodic emergence and receding as well as a forward mobility of an active anodic front. This behaviour could indicate a step-wise and discontinuous crack propagation mechanism. SEM images revealed the presence of a side crack adjacent to the main crack which confirms the presence of an expanded anodic front in SVET maps.

Low-Temperature Stress Corrosion Cracking of Austenitic and Duplex Stainless Steels Under Chloride Deposits

Corrosion performance of austenitic-ferritic (duplex) stainless steels UNS S32101, S32202, S32304, and S32205 and austenitic stainless steels UNS S30403 and S31603 was studied in the presence of ch...

Low-Temperature Stress Corrosion Cracking of Stainless Steels in the Atmosphere in the Presence of Chloride Deposits

Abstract Several cases of ceiling collapses and other failed elements have been reported in indoor swimming pool halls in the last two decades. The collapses were caused by stress corrosion crackin...

Hydrogen embrittlement of Ni-Cr-Fe alloys

The purpose of this work was to investigate the role of chromium on hydrogen embrittlement of Ni-Cr-Fe alloys and thus to develop a better understanding of the low-temperature stress corrosion cracking (SCC) phenomenon. The effect of chromium on hydrogen embrittlement was examined using tensile tests followed by material evaluation via scanning electron microscopy (SEM) and light optical microscopy. Four alloys were prepared with chromium contents ranging from 6 to 35 wt pct. In the uncharged condition, ductility, as measured by the percent elongation or reduction in area, increased as the alloy chromium content increased. Hydrogen appeared to have only minor effects on the mechanical properties of the low-chromium alloys. The addition of hydrogen had a marked effect on the ductility of the higher-chromium alloys. In the 26 pct chromium alloy, the elongation to failure was reduced from 53 to 14 pct, with a change in fracture mode from mixed ductile dimple and ductile intergranular failure to a brittle appearing intergranular failure. A maximum in embrittlement was observed in the 26 pct Cr alloy. The maximum in embrittlement coincided with the minimum in stacking-fault energy. It is proposed that the increased hydrogen embrittlement in the high-chromium alloys is due to increased slip planarity caused by the lower stacking-fault energy. Slip planarity did not appear to affect the fracture of the uncharged specimens.

Mechanisms of Stress-corrosion cracking of alloy X-750 in high-purity water

The high-strength, nickel-base alloy X-750 is susceptible to stress-corrosion cracking (SCC) in high-purity, deaerated water. Crack initiation occurs at high temperatures [>400°F (204 °C)]. Crack propagation occurs in both high-temperature and low-temperature [<300 °F (149 °C)] water. High-temperature crack growth rates are on the order of mils per day. Low-temperature cracking is extremely rapid [≈100 in. (250 cm) per day]. Three heat treatments of Alloy X-750 are investigated: (1) stress equalized—1625 °F (885 °C)/24 hours + 1300 °F (704 °C)/20 hours, (2) direct aged—1300 °F (704 °C)/24 hours, and (3) solution annealed and direct aged—2000 °F (1093 °C)/ 1 hour + 1300 °F (704 °C)/20 hours. Stress-equalized Alloy X-750 is most susceptible to SCC; solution-annealed and direct-aged Alloy X-750 is least susceptible. A hydrogen embrittlement model of SCC is developed that predicts SCC performance on the basis of grain boundary chemistry and grain boundary carbides. Phosphorus segregates to the grain boundary in concentrations of up to ≈700 times the bulk concentration during processing and heat treatment. Phosphorus at the grain boundaries increases susceptibility to high- and low-temperature SCC. The presence of M23C6-type carbides and /or the absence of MC-type carbides at the grain boundaries improves SCC performance in high-temperature water.

Effect of Thermal Stabilization on the Low Temperature Stress Corrosion Cracking of Inconel 600

Abstract The propensity of thermally stabilized Inconel 600 to undergo low temperature stress corrosion cracking (SCC) in sulfur bearing environments has been investigated with U-bends and slow strain rate testing. The results have been compared with those of sensitized Inconel 600. The potential dependence of crack propagation rate has been established in a single test by using several U-bends held at different potentials by choosing an appropriate electrical circuitry. The difference in SCC susceptibility of the sensitized and stabilized materials has been discussed in terms of the grain boundary chromium depletion and resultant intergranular attack in boiling ferric sulfate-sulfuric acid tests, and electrochemical potentiokinetic reactivation (EPR) tests.

Low Temperature Stress Corrosion Cracking of Sensitized Inconel 600 in Tetrathionate and Thiosulfate Solutions

Abstract This paper addresses some aspects of low temperature stress corrosion cracking (SCC) in Inconel 600 steam generator tubing, a recent instance of which apparently resulted from the contamination of the primary coolant by sulfur compounds. The low temperature SCC of sensitized Inconel 600 was studied in concentrated and dilute solutions of tetrathionate and thiosulfate. The material tested was a tubing directly sensitized from the mill-annealed condition. Tests were performed using U-bends, slow strain rate, and constant extension. The results show that the propensity to SCC, especially its initiation, in thiosulfate is low and is much lower than in tetrathionate. However, when slow strain rate was applied in thiosulfate, or when the pH of the thiosulfate solution was lowered, the specimens cracked readily. Constant extension tests, where the extension was applied using dynamic straining with the solution present, caused cracking much faster than in U-bends, suggesting that U-bend cracking is initi...

Environmental Variables in the Low Temperature Stress Corrosion Cracking of Inconel 600

Abstract The low temperature stress corrosion cracking of sensitized Inconel 600 has been examined using aerated 1.3% boric acid solutions with small additions of sodium thiosulfate. Cracking is observed for thiosulfate concentrations above 10−6 M. The rate of cracking increases with temperature to at least 80 C. Concentrated solutions with potential control give crack velocities up to about 0.4 μm/s at 22 C. Provided that cracks are initiated by slow straining, they continue to propagate at very low apparent stress intensities. Lithium hydroxide additions inhibit SCC by producing borate anions; the rate of borate to thiosulfate ion concentration is an important factor in determining immunity to SCC.

Low temperature stress corrosion cracking of Inconel 600 under two different conditions of sensitization

The low temperature stress corrosion cracking (SCC) of Inconel 600 under two different conditions of sensitization was studied in sulfur-bearing environments. In one case the material was sensitized directly from the mill annealed condition (MAS) and in the other, solution annealing followed by water quenching was used prior to sensitization (SAS). The propensity to SCC increased significantly by the SAS treatment, as revealed by dynamic tests in very dilute sodium thiosulfate or sodium tetrathionate solutions, and U-bend tests in a concentrated thiosulfate solution which failed to crack the MAS material. The implications of these observations are discussed in terms of the microstructures of the materials.

Chemical studies of polythionic acid stress-corrosion cracking

Low temperature stress corrosion cracking of sensitized stainless steel, promoted by aqueous solutions of polythionates S xO 6 2−, and related sulfur compounds, particularly thiosulfates, has been a long known problem in the petroleum industry and more recently has cropped up in the nuclear power industry. Membrane permeation results presented here show that S 4O 6 2− and S 2O 3 2− do not function simply as sources of sulfide to promote hydrogen permeation and embrittlement. They do promote anodic dissolution, also generating an unusual adsorption-related anodic spike in voltammetric scans. The oxidation of iron sulfide scales, said to be the source of the substances in petroleum refineries, has been shown to give rise mostly to Fe 2O 3 and elemental sulfur, with low yields of both S 4O 6 2− and S 2O 3 2−.