Corrosion and mechanical strength of welded joints of downcomers for RBMK reactors

Timofeev, B. T.; Karzov, G. P.; Gorbakony, Alexander; Nikolaev, Yu.K

doi:10.1016/s0308-0161(99)00005-8

Cited by 13 publications

(7 citation statements)

References 3 publications

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“…Some investigators have suggested [25,26,27] that while delta-ferrite increases during the welding process, many Crdepleted zones are probably formed because of microsegregation of Cr at the ferrite-austenite interphase boundaries and the interdendritics of ferrite are attacked by austennite due to the less stable passivity, leading to an increase of pitting corrosion susceptibility. However, in this study, as the low heat input and high cooling rate of the FCAW process did not offer sufficient time for chromium diffusion to microsegregate on the boundaries, a large quantity of chromium content may have still remained in the dendrite cores.…”

Section: Electrochemical Analysismentioning

confidence: 99%

Influences of Cr/Ni equivalent ratios of filler wires on pitting corrosion and ductility-dip cracking of AISI 316L weld metals

Kim

Sung

et al. 2011

Met. Mater. Int.

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To study the pitting corrosion of AISI 316L weld metals according to the chromium/nickel equivalent ratio (Creq/Nieq ratio), three filler wires were newly designed for the flux-cored arc welding process. The weld metal with delta-ferrite at less than 3 vol.%, was observed for ductility-dip cracking (DDC) in the reheated region after multi-pass welding. The tensile strength and yield strength increased with increasing Creq/Nieq ratio. The result of anodic polarization tests in a 0.1 M NaCl solution at the room temperature (25) for 45 min, revealed that the base metal and weld metals have a similar corrosion potential of −0.34 VSCE. The weld metal with the highest content of Cr had the highest pitting potential (0.39 VSCE) and the passivation range (0.64 VSCE) was higher than the base metal (0.21 VSCE and 0.46 VSCE, respectively). Adding 0.001M Na2S to the 0.1 M NaCl solution, the corrosion occurred more severely by H2S. The corrosion potentials of the base metal and three weld metals decreased to −1.0 VSCE. DDC caused the decrease of the pitting potential by inducing a locally intense corrosion attack around the crack openings.

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Section: Electrochemical Analysismentioning

confidence: 99%

Influences of Cr/Ni equivalent ratios of filler wires on pitting corrosion and ductility-dip cracking of AISI 316L weld metals

Kim

Sung

et al. 2011

Met. Mater. Int.

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“…2 specimen and the base metal. Some investigators have suggested [2][3][4] that while delta ferrite increases during welding process, many chromium-depleted zones are probably formed because of microsegregation of chromium at the ferrite-austenite interphase boundaries, leading to an increase of pitting corrosion susceptibility. However, in this study, as the low heat input and high cooling rate of the FCAW process did not offer sufficient time for chromium diffusion to microsegregate on the boundaries, a large quantity of chromium content may have still remained in the dendrite cores in No interdendritic attack.…”

Section: Tablementioning

confidence: 99%

“…However, exposure to a chloride atmosphere leads to severe, localized corrosion attack on passive metal weldments due to the microsegregation of chromium content on the ferriteaustenite interphase boundary during the cooling process [2][3][4]. The pitting corrosion phenomenon in thin plate austenitic SS with either TIG or MIG process has been extensively investigated by several authors [2,[5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Pitting corrosion behavior on crack property in AISI 304L weld metals with varying Cr/Ni equivalent ratio

et al. 2009

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“…In [6,10,12], it is shown that the ICCC of welded joints made of 08Kh18N10T steel depends on the following three basic factors: the level of stresses acting in the structure, chemical purity of the heat carrier [i.e., water circulating in the contour (its oxygen content)], and the degree of sensitization of the metal in the HAZ of welded joints. Intercrystalline corrosion cracking is a quite complicated phenomenon including various physical aspects and numerous parameters connected both with the properties of materials (chemical composition of the metal, welding procedures, etc.)…”

Section: Causes and Mechanisms Of The Appearance Of Defects In Pipelimentioning

confidence: 99%

“…2). The analysis of the stress-strain state shows that the total level of (tensile working and residual welding) stresses on the inner surface of the analyzed unit (which was not subjected to thermal treatment after welding) exceeds the yield strength of steel [6,13]. Moreover, the process of operation of nuclear power plants was accompanied by significant violations of the water-chemical conditions (connected with elevated concentrations of oxygen in the heat carrier) [14,15].…”

Section: Causes and Mechanisms Of The Appearance Of Defects In Pipelimentioning

confidence: 99%

Analysis of the events of failures of pipelines made of austenitic steel in nuclear power-generating industry

2006

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On the basis of the experience of long-term operation of nuclear power plants with RBMK (high-power channel reactors) and water-cooled water-moderated reactors, we analyze the events of failures of pipelines made of Kh18N10T steel. It is shown that the main mechanism of failures of welded joints in pipelines made of this type of steel is intercrystalline corrosion cracking. As the causes of the appearance of defects of this sort, one can mention the joint action of high levels of stresses, significant amounts of oxygen in the heat carrier, and sensitization of steel in the heat-affected zone of welded joints in pipelines. We propose compensating measures aimed at decreasing the negative effect of intercrystalline corrosion cracking in the process of operation.Introduction. The experience of operation of power-generating equipment at nuclear power plants in Russia and other countries shows that some elements of this equipment (for the most part, welded joints made of austenitic stainless steels) fail during the designed service life. According to the world statistics, up to 41% of the general number of these failures are caused by the action of the heat carrier. Among the most dangerous events of this sort, we can mention the failures of pipelines of the first contour. The common feature of all failures of pipelines made of 18-8 type steel is the formation of intergranular cracks either in the heat-affected zones (HAZ) of welded joints whose metal is sensitized in the process of welding or in elements made of metals subjected to sensitizing thermal treatment in the process of manufacturing. In the practice of operation of foreign nuclear power plants (USA, Germany, and Japan), this problem is of primary importance. At the same time, in Russia, it is customary to use 08Kh18N10T stabilized austenitic steel as a material of power-generating equipment. This type of steel is characterized by high stability in high-temperature oxygen-containing aqueous media. Nevertheless, numerous cases of crack initiation were detected in pipelines of stainless steel at different nuclear power plants equipped with RBMK (high-pow er channel reactors) after more than 50,000 h of operation.1. Defects in Pipelines. The problem of corrosion cracking of welded joints made of austenitic stainless steels appeared in the late 1960s. Defects in the form of cracks were first detected in the HAZ of welded joints of pipelines (∅ 6-8 inches) at two nuclear power plants in the USA (Dresden-1 and Oyster Greek-1). The phenomenon of corrosion cracking was recorded in the pipelines of the first contour made of AISI-304 and AISI-316 stainless steels both in boiling-water reactors (BWR) and pressurized-water reactors (PWR). Later, the problem of corrosion cracking at nuclear power plants in the USA became much more serious. Thus, 64 events of cracking were recorded in 1975. Moreover, in 1982 and1985, the number of events of this sort exceeded 400 and 800, respectively [1, 2]. Defects occurred mainly in pipelines of small diameters (< 25.4 cm). Although ...

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Corrosion and mechanical strength of welded joints of downcomers for RBMK reactors

Cited by 13 publications

References 3 publications

Influences of Cr/Ni equivalent ratios of filler wires on pitting corrosion and ductility-dip cracking of AISI 316L weld metals

Influences of Cr/Ni equivalent ratios of filler wires on pitting corrosion and ductility-dip cracking of AISI 316L weld metals

Pitting corrosion behavior on crack property in AISI 304L weld metals with varying Cr/Ni equivalent ratio

Analysis of the events of failures of pipelines made of austenitic steel in nuclear power-generating industry

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