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Environmental Degradation of Dissimilar Austenitic 316L and Duplex 2205 Stainless Steels Welded Joints

Topolska S., Łabanowski J.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 4

2107--2112

EN

The paper describes structure and properties of dissimilar stainless steels welded joints between duplex 2205 and austenitic 316L steels. Investigations were focused on environmentally assisted cracking of welded joints. The susceptibility to stress corrosion cracking (SCC) and hydrogen embrittlement was determined in slow strain rate tests (SSRT) with the strain rate of 2.2 × 10−6 s−1. Chloride-inducted SCC was determined in the 35% boiling water solution of MgCl2 environment at 125°C. Hydrogen assisted SCC tests were performed in synthetic sea water under cathodic polarization condition. It was shown that place of the lowest resistance to chloride stress corrosion cracking is heat affected zone at duplex steel side of dissimilar joins. That phenomenon was connected with undesirable structure of HAZ comprising of large fractions of ferrite grains with acicular austenite phase. Hydrogen assisted SCC tests showed significant reduction in ductility of duplex 2205 steel while austenitic 316L steel remains almost immune to degradation processes. SSR tests of dissimilar welded joints revealed a fracture in the area of austenitic steel.

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Pękanie korozyjne rurociągów wody amoniakalnej w instalacjach koksowni

Ziewiec A., Tasak E.

Hutnik, Wiadomości Hutnicze

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2011

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Vol. 78, nr 2

193-198

PL

W artykule przedstawiono wyniki badań przyczyn pękania rurociągów wody amoniakalnej w koksowni. Ustalono, że pęknięcia występujące zarówno w spoinach jak i w materiale rury są wynikiem pękania korozyjnego naprężeniowego, spowodowanego obecnością w wodzie związków azotu i siarkowodoru oraz zbyt dużych naprężeń rozciągających wynikających z niewłaściwej kompensacji zmian długości instalacji. Opierając się na badaniach mikroskopowych i fraktograficznych przedstawiono model pękania korozyjnego rurociągów wody amoniakalnej zawierającej siarkowodór i inne związki chemiczne.

EN

The paper presents studies of causes for cracking of ammonia water pipeline in the installations of cocking plant. It has been established that the cracks occurring both in the welded joints and base material of the pipe are due to stress corrosion cracking caused by the concentration of nitrogen compounds and hydrogen sulphide and excessive tensile stresses induced by wrong compensation of length of the installation. On the basis of the microstructural observations and fracture studies a model of corrosion cracking of ammonia pipelines containing hydrogen sulphide and other chemical compounds was presented.

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Hydrogen-induced intergranular embrittlementt of ni-base alloys used for steam generator tubes

Coudurier A., Odemer G., Chene J., Raquet O.

Advances in Materials Science

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2007

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Vol. 7, nr 1(11)

124-132

EN

The hydrogen-induced intergranular rupture of alloys 600, 690 and 82 has been investigated in order to improve the understanding of the possible role of hydrogen on the Stress Corrosion Cracking (SCC) sensitivity of these alloys when exposed to primary water in Pressurized Water Reactors (PWR). Small tensile specimens were hydrogenated at 150°C by cathodic charging in molten salts in order to introduce a controlled amount of hydrogen homogeneously distributed in the samples. The hydrogen concentration in the samples and its dependence on the alloys chemistry and microstructure and on additional desorption annealing was measured by using the thermal fusion method. The role of H on the strain hardening and on the tensile properties of the alloys was investigated at room temperature. SEM was used to characterize the extent of H-induced intergranular cracking. Hydrogenated samples exhibit a strong H-induced ductility lass associated with intergranular fracture. The extent of both the ductility lass and the intergranular rupture strongly depends on the chemical composition and on the microstructure of the alloys. Alloy 82, representative of the weld alloy 600, exhibits the largest HE susceptibility whereas alloy 690 is the less affected by H absorption. The tensile properties recorded after desorption annealing illustrate the reversible character of H-induced intergranular rupture and demonstrate the predominant role, in the mechanism responsible for the ductility lass, of diffusible hydrogen and its interaction with defects involved in the plastic deformation such as dislocations.

4

Stress Corrosion Cracking Evaluation of High Alloy Steel (X2CrNiMoN 22-5-3) by DET

Lasek S., Blahetová M., Číhal V.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2004

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z. 78

17-22

EN

Stress corrosion cracking (SCC) can cause a dangerous failure of structural parts under specific combination of material, environment and loading. For testing of the resistance to SCC at higher temperatures (100-300°C) in water environments were proposed several methods. The Drop Evaporation Test (DET) is useful for comparison and evaluation of resistance of stainless steels and related alloys to SCC in chlorides containing water environments [1,2]. This test is valid in the cases, when evaporation of water environments can increase the content of anions (Cl-) and there is also possibility to form a salt deposition as a crevice on material surface. The advantage of DET is possibility of testing at higher temperature in the range 100~500°C using a lower Cl- water content (0-100 ppm) in convenient gas around the specimen. During DET there is a good possibility to observe a sample surface, initiation and propagation of pitting and corrosion cracking [3]. The process of thermal and corrosion fatigue is superposed on SCC mainly in the stage of initiation and propagation of short cracks especially in case of a higher difference of temperature between drops and heated sample. The DET simulates also the influence of heat transfer from material into environment on localized corrosion under evaporating conditions. The aim of this contribution is the study of short corrosion cracks growth on duplex steel of type X2CrNiMoN 22-5-3 (1.4462) under DET conditions by travelling microscope method.