Stress corrosion cracking (SCC) susceptibility of the phosphorus de-oxidized copper has been evaluated in synthetic seawater polluted by sulfides using slow strain rate test (SSRT). The effect of concentration of sulfide, temperature, and applied cathodic and anodic potentials on the final strain values and maximum stress were also studied. No cracks were found under the tested conditions. The final strain and maximum stress values decreased but not significantly, with increase in the temperature, applied anodic potential and sulfide concentration. The observed effect is due to the section reduction by uniform corrosion. Lateral cross section and microscopic examination of the fractured specimen ruled out the existence of the localized corrosion. Electrochemical measurements showed that the Cu2S film is not a protective film and also exhibits a mass transfer limitation to the inward diffusion of the sulfides. Based on these results the reasons for the absence of cracking are also discussed.

Stress corrosion cracking of a 14 wt% Cr martensitic stainless steel, with commercial names PH-15Cr5Ni, FV520B or X4CrNiCuMo15-5, used for the manufacture of low pressure turbine blades, has been studied with the intention of gaining a better understanding of the processes involved, how they occur and why. Industrially this is very important as stress corrosion cracking is considered to be a delayed failure process, whereby microscopic cracks can potentially propagate through a metal undetected until catastrophic failure occurs. The aim of this work is to establish links between crack length and external factors, such as exposure time, in order to devise a method of dating stress corrosion cracks and therefore predicting their possible occurrence in-service.

Lifetime prediction of components in Alloy 600 is a major concern for nuclear power plants. Alloy 600 components have been shown to be susceptible to stress corrosion cracking (SCC). In the 1990’s, an engineering model was developed in order to predict the life time as a function of the main macroscopic parameters (stress, environment, material), based on laboratory results. This model has since been used to predict the ranking of various Alloy 600 components, using the knowledges of the manufacturing and service conditions for each component. It was applied successfully in the case of forged control rod drive mechanism (CRDM) nozzles. However, it was found necessary to improve this model to account for the strain history of the different components. Predictions using the model, investigated from an array of test results on Alloy 600 in laboratory primary water, have demonstrated that the time for initiation differed significantly according to the strain path applied to the specimen. The present work is dedicated to assess SCC results from samples with different strain paths and different level of cold work in order to better understand the manufacturing conditions on SCC. The samples are machined in three different directions and tested at different durations in order to model the time for transition (transition between slow and fast propagation) as a function of cold work, strain path and stress. Thermomechanical treatments are also applied on two different heats of Alloy 600: forged WF675 (very susceptible to SCC in as received conditions) and rolled 78456/337 (non susceptible to SCC in as-received conditions) in order to transform the forged microstructure into a microstructure close to the rolled microstructure and vice-versa. These microstructures are then tested in primary conditions and the results are compared to the results obtained on as-received material in order to get a better understanding of manufacturing process and microstructure parameters regarding SCC behaviour.

Chloride-induced stress corrosion cracking (CISCC) has been identified as the main degradation mechanism for spent nuclear fuel dry storage canisters. This type of induced cracking is complex and depends on several factors, such as material composition, exposure temperature, relative humidity, applied tensile stress, and atmospheric salt concentration. An accelerated experiment was designed to simulate marine environments in a controlled fogging chamber to examine 304 and 304L stainless steel U-bend and welded U-bend samples. The samples were exposed to chloride rich and humid fogging in a corrosion chamber at 35℃ continuously for 4 weeks, 8 weeks, and 12 weeks. The same experiment was repeated at 50℃ for 4 weeks, 8 weeks, and 14 weeks to study the sensitivity of CISCC to temperature changes. A qualitative evaluation of optical micrographs from a 3D Surface Profiler was performed for 16 corroded samples and compared with 2 reference samples. Cracking was observed on 12 out of 16 samples exposed to 35℃ and 50℃ for durations ranging from 8 to 14 weeks. Likely cracking observations were noted on 4 out of 16 samples. A quantitative statistical analysis was also performed using surface profile depth (valley) data from corroded and reference samples. The quantitative analysis examined the effect of temperature, welding, exposure duration, and material composition. The quantitative results were compared with the qualitative results and literature published in CISCC. / Master of Science / Most nuclear power plants are currently using dry storage canisters (DSCs) which are made of a concrete vault and a stainless steel canister that houses the spent nuclear fuel (SNF) assemblies. Multiple conditions must be present simultaneously for chloride-induced stress corrosion cracking (CISCC) to develop, such as the presence of a susceptible alloy, high relative humidity, high temperature, high atmospheric salt concentrations, and applied tensile stresses. DSCs are typically made from 300-series austenitic stainless steels which are susceptible to this type of corrosion during long-term storage near marine environments. Therefore, understanding of the factors leading to CISCC is critically important for proper management and mitigation and to estimate the service life of DSCs for the safe long-term storage of SNF. An accelerated experiment was designed to examine the effects of temperature, exposure duration, and welding on pitting and cracking for 304 and 304L U-bend samples. The experimental results concluded that stainless-steel grades 304 and 304L are susceptible to CISCC when exposed for 8 weeks or longer to fogging at temperatures between 35℃ and 50℃, 95% relative humidity, and 5% salt concentration. This study also concluded that increasing exposure duration from 8 to 12 weeks or the temperature from 35℃ to 50℃ had no significant effect on the acceleration of CISCC. Also, unwelded samples were deemed more susceptible to CISCC than welded samples and the susceptibility of 304 and 304L grades were relatively similar.

Aluminum-magnesium alloy (AA5083-H116) is primarily designed for marine applications such as in ship hulls and deckhouses. Its excellent combination of physical and mechanical properties makes it useful for other applications such as aircraft construction, military equipment and vehicles and automobiles.<p>This study investigated the effect of time and temperature of sensitization on the mechanical and chemical properties of AA5083-H116 such as tensile strength, yield strength and susceptibility to intergranular corrosion (IGC). Test specimens were sensitized at various temperatures (80oC, 100oC, 175oC and 200oC) for up to 672 h (4 weeks). Microhardness measurements, tensile testing, scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), inductively coupled plasma/mass spectrometry (ICP/MS) and nitric acid mass loss tests (NAMLT) were used to evaluate these effects. <p>The results obtained show that the mechanical properties of AA5083-H116 deteriorated with increasing sensitization temperature and time. The adverse effect on these properties was attributed to reduction in dislocation density and recrystallization at higher temperatures. The as-received specimens and those sensitized at 80oC showed no susceptibility to IGC. However, at higher sensitization temperatures and longer resident times, resistance to IGC decreased dramatically. The reduction in IGC resistance was attributed to precipitation of secondary phases along the grain boundaries.

The stress corrosion cracking (SCC) condition for Alloy 600 was determined for various stress modes: constant-strain standard C-ring, and indentation, used to localize cracks for interrogation with x-ray techniques such as micro Laue diffraction (MLD). The SCC cracks nucleated on both the indentation edge, where finite element analysis showed that the maximum residual tensile stresses lie, and the surface in tension (bulge) on 150-kgf conically indented mill-annealed specimens (0.02 wt% C) in de-aerated solution of 10% caustic at 150 mVRE (pseudo-reference: A600), 315 OC for 48 hr. On the C-rings, the cracks nucleated at the lateral outer surface of apex, where maximum tensile stresses lie, in less than 12 hours, and propagated into the cross section. Also, corrosion tests on as-received A600 30-min ZrO2 surface mechanical attrition treated (SMAT) specimens suggested an intergranular attack type of behavior in 50% caustic at 210 mVRE (pseudo-reference: A600), 280°C for 24 hr.

The stress corrosion cracking (SCC) condition for Alloy 600 was determined for various stress modes: constant-strain standard C-ring, and indentation, used to localize cracks for interrogation with x-ray techniques such as micro Laue diffraction (MLD). The SCC cracks nucleated on both the indentation edge, where finite element analysis showed that the maximum residual tensile stresses lie, and the surface in tension (bulge) on 150-kgf conically indented mill-annealed specimens (0.02 wt% C) in de-aerated solution of 10% caustic at 150 mVRE (pseudo-reference: A600), 315 OC for 48 hr. On the C-rings, the cracks nucleated at the lateral outer surface of apex, where maximum tensile stresses lie, in less than 12 hours, and propagated into the cross section. Also, corrosion tests on as-received A600 30-min ZrO2 surface mechanical attrition treated (SMAT) specimens suggested an intergranular attack type of behavior in 50% caustic at 210 mVRE (pseudo-reference: A600), 280°C for 24 hr.

Aluminum-magnesium alloy (AA5083-H116) is primarily designed for marine applications such as in ship hulls and deckhouses. Its excellent combination of physical and mechanical properties makes it useful for other applications such as aircraft construction, military equipment and vehicles and automobiles.<p>This study investigated the effect of time and temperature of sensitization on the mechanical and chemical properties of AA5083-H116 such as tensile strength, yield strength and susceptibility to intergranular corrosion (IGC). Test specimens were sensitized at various temperatures (80oC, 100oC, 175oC and 200oC) for up to 672 h (4 weeks). Microhardness measurements, tensile testing, scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), inductively coupled plasma/mass spectrometry (ICP/MS) and nitric acid mass loss tests (NAMLT) were used to evaluate these effects. <p>The results obtained show that the mechanical properties of AA5083-H116 deteriorated with increasing sensitization temperature and time. The adverse effect on these properties was attributed to reduction in dislocation density and recrystallization at higher temperatures. The as-received specimens and those sensitized at 80oC showed no susceptibility to IGC. However, at higher sensitization temperatures and longer resident times, resistance to IGC decreased dramatically. The reduction in IGC resistance was attributed to precipitation of secondary phases along the grain boundaries.

This study investigated localized corrosion behavior of austenitic stainless steels under stressed and unstressed conditions, as well as corrosion of metallic thin films. While austenitic stainless steels are widely used in corrosive environments, they are vulnerable to pitting and stress corrosion cracking (SCC), particularly in chloride-containing environments. The corrosion resistance of austenitic stainless steels is closely tied to the alloying elements chromium, nickel, and molybdenum. Polarization curves were measured for five commercially available austenitic stainless steels of varying chromium, nickel, and molybdenum content in 3.5 wt.% and 25 wt.% NaCl solutions. The alloys were also tested in tension at slow strain rates in air and in a chloride environment under different polarization conditions to explore the relationship between the extent of pitting corrosion and SCC over a range of alloy content and environment. The influence of alloy composition on corrosion resistance was found to be consistent with the pitting resistance equivalent number (PREN) under some conditions, but there were also conditions under which the model did not hold for certain commercial alloy compositions. Monotonic loading was used to generate SCC in in 300 series stainless steels, and it was possible to control the failure mode through adjusting environmental and polarization conditions. Metallic thin film systems of thickness 10-200 nm are being investigated for use as corrosion sensors and protective coatings, however the corrosion properties of ferrous thin films have not been widely studied. The effects of film thickness and substrate conductivity were examined using potentiodynamic polarization and scanning vibrating electrode technique (SVET) on iron thin films. Thicker films undergo more corrosion than thinner films in the same environment, though the corrosion mechanism is the same. Conductive substrates encourage general corrosion, similar to that of bulk iron, while insulating substrates supported only localized corrosion.

Stress corrosion cracking (SCC) of alloy 600 is regarded as one of the most important challenges to nuclear power plant operation worldwide. This study investigates two heats of alloy 600 (forged control rod drive mechanismnozzle and rolled divider plate) in order to obtain a better understanding of the effects of the material parameter on the SCC phenomenon. The experimental approach was designed to determine the effect of the manufacturing process (forged vs. rolled), the cold-work (as-received vs. cold-worked) and the strain path (monotonic vs. complex) on SCC of alloy 600. Specimens with different strain paths have been produced from two materials representative of plant components and tested in high temperature (360°C) high pressure primary water environment. The manufacturing process has been proven to have a great effect on the stress corrosion cracking behaviour of alloy 600. Indeed, the SCC susceptibility assessment has demonstrated that the rolled materialis resistant to SCC even after cold work, whereas the forged material is susceptible in the as-received state. Microstructural characterisations have been undertaken to explain these differences in SCC behaviour. The carbide distribution is the main microstructural parameter influencing SCC but the misorientation, in synergy with the carbide distribution, has been proven to give a better representation of the materials SCC susceptibilities.