Chloride-induced Stress Corrosion Cracking Research Articles

Stress Corrosion Cracking of Stainless Steel Expansion Joint for Heat-Supply Network

Tree-like transgranular cracks were found at the bottom of a expansion joint bellow that had been used for heat-supply network at 90°C and 0.8MPa. A failure analysis was conducted, including visual, microstructural, compositional, and mechanical characterization, to determine the cause and source of the degradation. Branched, brittle cracks were observed in the failure region and exhibited transgranular propagation. The results showed that the concentration of the chloride in the deposit was 248 ppm in the intermittent wet/dry cycles situation. It was determined that the likely cause of failure was neutral pH, Concentrated chloride-induced stress corrosion cracking.

Probing propensity of grade 2205 duplex stainless steel towards atmospheric chloride-induced stress corrosion cracking

The propensity of grade 2205 duplex stainless steel towards atmospheric chloride-induced stress corrosion cracking at 50°C has been investigated. Electron backscatter diffraction has been used to characterise as received and 750°C heat-treated microstructures. Screening tests in chloride-containing aqueous environments were employed to investigate the corrosion behaviour of both microstructures. These tests indicated significantly increased corrosion rates when exposed to HCl or FeCl3-containing environments. Stress corrosion cracking tests with atmospheric exposures for up to 12 months showed selective dissolution of the ferrite, accompanied by stress corrosion microcracks in the austenite. This work demonstrates that grade 2205 duplex stainless steel microstructure may be rendered susceptible to stress corrosion cracking under atmospheric exposure conditions at 50°C.

Assessing the risk of under-deposit chloride-induced stress corrosion cracking in austenitic stainless steel nuclear waste containers

This paper provides a short summary of investigations that have focused on the occurrence of the phenomenon that is commonly referred to as atmospheric chloride-induced stress corrosion cracking (AISCC) in types 304L and 316L austenitic stainless steels; the materials from which storage containers for the UK’s intermediate level nuclear waste are currently fabricated. A brief overview of the relationship between localised corrosion phenomena (pitting or crevice corrosion) and stress corrosion cracking from observations derived under conditions of immersion in chloride-containing environments is provided. The impact of environmental variables such as the relative humidity, temperature and chloride deposition density on the development of AISCC and potential difficulties in extrapolating data derived from laboratory investigations to an in-store situation are also discussed. Proposals for the development of laboratory protocols that may more accurately reflect behaviour in an actual storage situation, including the possibility of employing accelerated testing methods, are also briefly addressed.

Under-Deposit Chloride-Induced Stress Corrosion Cracking in Austenitic Stainless Steels: Aspects Associated with Deposit Type, Size and Composition

The occurrence of Atmospheric chloride-Induced Stress Corrosion Cracking (AISCC) in austenitic stainless steels beneath ‘wetted’ deposits of either artificial sea-salt, organically-enriched artificial sea-salt or MgCl2.6H2O has been investigated under controlled climatic conditions (40°C and 33% Relative Humidity). The presence of organic exudate in relatively large artificial sea-salt deposits (~3 mm diameter) appears to markedly decrease the induction time associated with AISCC; cracking occurred within a week in one U-bend specimen, well inside the ~12 week period usually observed under ‘wetted’ deposits of artificial sea-salt alone. Cracks appear to initiate from crevices formed under NaCl crystals. It is tentatively proposed that the organic species promotes greater coverage by the MgCl2 electrolyte in the vicinity of these crystals. This increases the probability of crevice initiation, and allows more rapid production of localized corrosion sites (pits or crevices) propagating under conditions that allow the transition to AISCC (pit/crevice dissolution rate < crack velocity).

Chloride-Induced Stress Corrosion Cracking in 316Ti Fuel Oil Pipes of a Gas Turbine Power Plant

Abstract Two bent pipe sections of the fuel oil system of a heavy-duty gas turbine engine had to be disassembled due to leakage. One of the two specimens received by the laboratory of the engine manufacturer featured a sub-standard weld repair performed by customer personnel. A metallurgical failure investigation was ordered to determine the root cause of the leakage and to verify the results of a laboratory investigation already performed by a third party at the customer's request. The repair-welded bent pipe section failed due to halide-induced pitting corrosion that propagated through-wall in a transgranular stress corrosion cracking (SCC) mode.

Towards a more Realistic Experimental Protocol for the Study of Atmospheric Chloride-Induced Stress Corrosion Cracking in Intermediate Level Radioactive Waste Container Materials

ABSTRACTThe occurrence of Atmospheric chloride-Induced Stress Corrosion Cracking (AISCC) under wetted deposits of MgCl2 or sea-salt at 70°C has been investigated at various Relative Humidities (RH). The appearance of AISCC is a function of the environmental RH. At 33% RH (the deliquescence point of MgCl2), AISCC generated under MgCl2 or sea-salt deposits is of a similar appearance with regards to the number of cracks produced and average crack length. At 50% RH sea-salt seems to be more aggressive at least in terms of crack frequency. This observation may highlight the significance of carnallite (KMgCl3.6H2O) in promoting AISCC in types 304L and 316L stainless steels. The use of accelerated testing methods to validate apparent thresholds in chloride deposition density and other critical factors that influence the initiation and propagation of AISCC is briefly discussed.

Under-Deposit Chloride-Induced Stress Corrosion Cracking in Austenitic Stainless Steels: Aspects Associated With Deposit Type, Size and Composition

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Transgranular stress corrosion cracking of 304L stainless steel pipe clamps in direct use geothermal water heating applications

Direct use geothermal heating relies on heat extracted from naturally occurring geothermal water sources to provide heating needs for commercial and residential use. The city of Boise, Idaho maintains the largest district geothermal heating system in the United States, utilizing a source of geothermal water at 80°C. 304 Stainless steel (UNS S30400) pipe clamps are used throughout the system as repair seals and for new service connections. Occasionally unexpected fracture of the stainless steel clamps occurs with time-in-service periods as short as 1year. A failure analysis was conducted, including visual, microstructural, compositional, and mechanical characterization, to determine the cause and source of the degradation. Cracking of the clamps was limited to localized regions with the remainder of the clamp unaffected. Branched, brittle cracks were observed in the failure region and exhibited transgranular propagation. Based on the temperature, available moisture, stress level, and type of material used it was determined that the likely cause of failure was neutral pH, dilute chloride-induced stress corrosion cracking. Based on this failure analysis, geothermal or other buried heated water systems must consider protective measures or more SCC-resistant materials to prevent susceptible conditions from developing, compared to conventional water systems, to ensure maximum lifetime performance.

Chloride-Induced Stress Corrosion Cracking of Austenitic Stainless Steel Used for Dry Storage of Spent Nuclear Fuel

Some dry cask storage system (DCSS) designs utilize austenitic stainless steel canisters surrounded by concrete shielding structures to store spent nuclear fuel (SNF) at Independent Spent Fuel Storage Installations (ISFSIs). ISFSIs that are located where chlorides can be deposited on the canisters may have the potential for initiating chloride-induced stress corrosion cracking (SCC). Susceptibility to chloride-induced SCC depends on the environmental conditions at the canister surface, including the following key parameters: temperature; relative humidity (RH); areal density, composition and aqueous concentration of deposited salts; and the stress state of the canister, particularly in the weld and the weld heat affected zone (HAZ). National and international literature was reviewed to understand threshold values and uncertainties associated with these key parameters. Current models have uncertainties associated with salt deposition rate, local humidity and aqueous chemistry on the canister surface, salt composition and water volume, gamma radiolysis, and laboratory test methods.

Chloride-Induced Stress Corrosion Cracking of Austenitic Stainless Steel for Dry Storage of Spent Nuclear Fuel

not Available.

Development of a prototype pipework scanning system based upon energy dispersive X-ray diffraction (EDXRD)

A prototype pipework scanning system based upon energy dispersive X-ray diffraction (EDXRD) has been produced, for which system development and preliminary results are presented here. This apparatus has been developed from experience with 2D and 3D bench-top EDXRD systems and comprises a conventional industrial X-ray tube coupled to a bespoke design of tungsten collimators and compact CdTe detector. It is designed as a robust system, rather than delicate lab-based system, to investigate sections of stainless steel pipework for structural changes induced through quenching the steel in liquid nitrogen, and damaging effects such as chloride-induced stress corrosion cracking (SCC). Given the properties of tungsten, namely its brittle nature, a complex programme of electro-discharge machining (EDM) has been devised to precisely manufacture the collimators from a series of sintered tungsten blocks. Preliminary measurements have focused on calibrating the system using the extreme ferrite and austenite phases, meeting a pre-requisite benchmark for attempting more challenging measurements such as the austenite to martensite transformation and investigations of SCC in these sections of pipework.

Chloride induced stress corrosion cracking of candidate canister materials for dry storage of spent fuel

Susceptibility to chloride induced stress corrosion cracking (ESCC) of candidate canister materials, UNS S31260 and UNS S31254 stainless steels (SS), was investigated by a constant load test in air at temperatures of 343 and 353 K with relative humidity (RH) of 35%, and at 373 K without controlling RH. UNS S31260 and UNS S31254 SS did not fail until 37,700 h at 353 K with RH = 35%, where UNS S30403 SS failed within 250–500 h. The same tendency also was obtained at 343 K, suggesting the superior ESCC resistance of UNS S31260 and UNS S31254 SS. Even rust was not observed on the specimens tested at the temperature of 373 K. To explain the higher ESCC resistance, the pitting potential was measured in the saturated synthetic sea water at temperatures from 303 to 353 K, since ESCC is usually associated with localized corrosion such as pitting and may be closely related to the corrosion resistance. The pitting potentials of UNS S31260 and UNS S31254 SS were much higher than that of UNS S30403 SS. Thus, it was concluded that the superior ESCC resistance is attributable to the higher resistance of UNS S31260 and UNS S31254 SS to pitting corrosion. The critical relative humidity for ESCC, under which no ESCC occurs, is equal to or higher than 15% at temperatures < 353 K judging from ESCC behavior of UNS S30400 SS.

Stress Corrosion Cracking Growth Rates of Candidate Canister Materials for Spent Nuclear Fuel Storage in Chloride-Containing Atmosphere

Chloride-induced stress corrosion crack growth rates were measured for candidate canister materials in a simulated marine atmospheric environment. Half-inch compact tension specimens were used to obtain stress corrosion crack growth rates by applying a direct-current potential-drop method to measure crack lengths. The crack growth rates of S31603 and S31260 stainless steels were 3 � 10 � 10 ms � 1 and 4 � 10 � 13 ms � 1 for an applied stress intensity factor of 30 MPam 0:5 , respectively, at a test temperature of 353 K at a relative humidity of 35%. S31254 specimens did not show stress corrosion cracking susceptibility under the same conditions as above, suggesting their superior resistance to chloride-induced stress corrosion cracking. These data were consistent with the results that S31260 and S31254 stainless steels did not fail after up to 37700 h although S31603 failed after 533 h in constant-load tests under the same environmental conditions. Assuming active-path corrosion to be an anodic subprocess of stress corrosion crack growth, anodic polarization curves of the test materials were obtained in a synthetic seawater solution of pH 1 at 353 K. The maximum anodic current density of the active dissolution of S31603 stainless steel was ten times as large as that of S31260 stainless steel. This result qualitatively explains the difference in the crack growth behavior between S31603 and S31260 stainless steels. (doi:10.2320/matertrans.MRA2006367)

Chloride-induced stress corrosion cracking of furnace burner tubes

The burner tubes (316SS) of an ethylene cracking furnace in a Saudi petrochemical plant experienced repeated premature failures. One failed sample was investigated by chemical and microstructural analytical techniques to find out the failure cause and provide preventive measures. The results indicate that the burner tube failed due to chloride-induced stress corrosion cracking (SCC). Chloride could be due to the contamination coming from the ambient industrial environment. The forming process (bending and drawing) of the tubes prior to installation introduced residual tensile stresses necessary for SCC. It is recommended to stress relieve (or shot peen) the tubes following the forming process, or alternatively apply protective coatings (chloride-free) to prevent contamination. Periodic cleaning of the tube exterior is necessary.

Failure Propensity of Austenitic Stainless Steels by Chloride Induced Stress Corrosion Cracking in Air

Failure Propensity of Austenitic Stainless Steels by Chloride Induced Stress Corrosion Cracking in Air

Corrosion resistance of the high‐strength filler metal NiCr20Fe14Mo11WN (alloy 50 PLUS)

AbstractThe Nb‐free NiCr20Fe14Mo11WN alloy has been developed as a new filler metal which combines high strength and excellent corrosion resistance in wet environments at ambient temperatures.The alloy is characterized by exceptional resistance to pitting and crevice corrosion, no sensitiveness to chloride induced stress corrosion cracking and shows high mechanical properties, e.g. 0.2 %‐yield strength.Because the alloy is practically free of stable nitride formers like niobium, titanium etc., no nitride formation during welding of super austenitic, duplex and super duplex steels is possible, which proves the alloy to be superior to alloy 625.

Failure of a super duplex stainless steel reaction vessel

Crevice corrosion and stress corrosion cracking (SCC) were recently discovered in a vessel used to strip vinyl chloride monomer from a water-based slurry of PVC granules. The vessel was manufactured from UNS S32750 super duplex stainless steel and the welds were produced using matching welding consumables. Although localised corrosion might have been expected, the occurrence of SCC was inconsistent with the majority of the published literature: in particular, the nominal operating temperature should have been too low for chloride-induced SCC of super-duplex stainless steel. However, damage was found mainly in the vicinity of the circumferential and longitudinal welds, and part of the subsequent failure investigation was therefore focused on the possibility of poor weld quality being the cause of failure. This task was approached primarily by measuring the influence of welding parameters on the value of the critical pitting temperature (CPT), and attempting to correlate the results with observed changes in the weld microstructure. CPT values were determined by a potentiodynamic method, using samples cut from the failed vessel and from a range of reference welds manufactured using known welding parameters.

Chloride Induced Stress Corrosion Cracking of Type 304 and 304L Stainless Steels in Air

Chloride Induced Stress Corrosion Cracking of Type 304 and 304L Stainless Steels in Air

Chloride-Induced Stress Corrosion Cracking of Powder Metallurgy Duplex Stainless Steels

Abstract The chloride-induced stress corrosion cracking (SCC) resistance of nitrogen-alloyed, powder metallurgically (P/M) produced and hot isostatically pressed (HIP) duplex stainless steels (DSS)...

The chloride stress-corrosion cracking behavior of stainless steels under different test methods

Chloride-induced stress-corrosion cracking (SCC) is one of the failure modes of stainless steels. Highly alloyed austenitic stainless steels S32654, S31254, and N08028, and duplex grades S32750 and S31803 possess much improved resistance to SCC compared with S30400 and S31600 steels. With the development of a database, SSData, experimental data collected from calcium chloride tests, autoclave tests, and drop evaporation tests were evaluated. Stress-corrosion cracking data generated by autoclave tests agreed well with the practical service conditions and can be used to discriminate alloys for SCC resistance in sodium chloride solution. Drop evaporation test data can be used in situations where evaporation may occur and cyclic loading may be involved. The SCC resistance of alloys under each method increased with increasing molybdenum equivalent Mo + 0.25Cr + 0.1Ni. For a given alloy, the testing result depends on the stress state and environment; different test methods can give different ranking orders concerning SCC resistance. The performance of duplex stainless steels in a chloride-containing environment at higher temperatures was not as good as expected when dynamic loading was involved.