Liquid metal induced embrittlement in fuel line braze joints

Maciejewski, J.

doi:10.1361/15477020522960

Cited by 12 publications

(9 citation statements)

References 5 publications

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“…4(a)-(c). The cracks were considered to be responsible for the wetting and penetration of liquid copper into grain boundaries of austenitic steel when there was an intimate contact between liquid copper and austenitic steel under certain stress concentration at a high temperature [9][10][11][12]. In the joint brazed by copper based brazing filler, the cracks initiated at the interface between fusion zone and HAZ and propagated from HAZ to metal zone to form net-like intergranular cracks, as shown in Fig.…”

Section: Effects Of Brazing Filler and Methods On Iter Thermal Anchor mentioning

confidence: 99%

“…Therefore, whether the brazing filler contains copper or not and what the relative copper content in copperbased or copper-contained brazing filler are quite important for the formation and shape of copper penetrating cracks [9,10]. Further, the solidification cracks and liquation cracks that are usually detected in austenitic steel joints [9,12] are not observed in the thermal anchor joints welded by 316L and pure nickel brazing fillers, respectively. Figure 5 shows the joint welded by vacuum brazing using CuSi3Mn filler.…”

Section: Effects Of Brazing Filler and Methods On Iter Thermal Anchor mentioning

confidence: 99%

“…The stress concentration of the whole thermal anchor joint produced by the heating in vacuum brazing is less than that by TIG arc brazing, which is contributed to no copper penetrating crack formed in the joint, even though there is an intimate contact between liquid copper and austenitic steel at 1150 C for 30 min. Therefore, whether there is enough stress concentration in brazing process has a significant influence on the formation of copper penetrating crack in thermal anchor joint [9,10]. Figure 6 shows the SEM images of copper penetrating cracks in thermal anchor joints of TIG arc brazing with CuSi3Mn and Ag45CuSnNi brazing fillers, respectively.…”

Section: Effects Of Brazing Filler and Methods On Iter Thermal Anchor mentioning

confidence: 99%

“…The copper penetrating cracks in thermal anchor joints are caused principally by the penetration of copper constituent of the brazing filler into austenitic grain boundaries of the base metal. The surface stress concentration and the intimate contact between liquid copper and austenitic steel surface are the two main formative factors for these cracks [9][10][11]. The special grain boundary conditions (serious lattice distortion, high distortion energy, and high stress concentration) [12] provide a great probability for liquid copper penetrating into boundaries; the surface energy and atomic binding forces of austenitic grain boundaries can be brought down by the copper penetration.…”

Section: Effects Of Brazing Filler and Methods On Iter Thermal Anchor mentioning

confidence: 99%

“…However, liquid copper and solid austenitic steel are well known as an embrittlement couple, which can cause liquid metal-induced embrittlement (LMIE) of austenitic steel when there is an intimate contact between liquid copper and austenitic steel under certain stress concentration at a high temperature, and then the intergranular copper penetrating cracks are formed [9][10][11][12]. Considering the large forces that the gravity magnet supports will endure, the copper penetrating cracks may seriously affect the normal function and service life of the whole system, so these cracks should be strictly controlled and avoided.…”

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confidence: 99%

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Effects of Brazing Filler and Method on ITER Thermal Anchor Joint Crack

Chen¹,

Wu²,

Pei³

et al. 2014

Materials and Manufacturing Processes

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Thermal anchor, one of the key components to keep temperature balance of gravity magnet support, should be avoided welding defects in its welding joints, which endure large forces when the international thermonuclear experimental reactor (ITER) fusion device is operating. The influences of brazing fillers and brazing methods on the cracks in joints of thermal anchor were investigated by microstructure analysis. The results have shown that the copper penetrating cracks were observed in the heat-affected zone (HAZ) of tungsten inert gas (TIG) arc brazing joints welded by CuSi3, CuSi3Mn, and Ag45CuSnNi brazing fillers, which are chiefly responsible for the diffusion and penetration of copper, derived from molten brazing filler metal into the 316L/316LN austenitic grain boundaries leading to embrittlement. The intimate contact between liquid copper and austenitic steel surface and the surface stress concentration of the austenitic steel are the main formative factors for the copper penetrating cracks. Adopting brazing fillers without containing copper or employing vacuum brazing can effectively avoid the copper penetrating cracks in the joints of ITER thermal anchor.

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Section: Effects Of Brazing Filler and Methods On Iter Thermal Anchor mentioning

confidence: 99%

Section: Effects Of Brazing Filler and Methods On Iter Thermal Anchor mentioning

confidence: 99%

Section: Effects Of Brazing Filler and Methods On Iter Thermal Anchor mentioning

confidence: 99%

Section: Effects Of Brazing Filler and Methods On Iter Thermal Anchor mentioning

confidence: 99%

Section: Please Scroll Down For Articlementioning

confidence: 99%

See 3 more Smart Citations

Effects of Brazing Filler and Method on ITER Thermal Anchor Joint Crack

Chen¹,

Wu²,

Pei³

et al. 2014

Materials and Manufacturing Processes

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Cracking of Copper Brazed Steel Joints Due to Precipitation of MnS upon Cooling

Varanasi

Koncz-Horváth

Sycheva

et al. 2020

J. of Materi Eng and Perform

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The process of brazing of different steel grades by pure liquid copper foil was studied to reveal the critical conditions when cracks do or do not appear in the braze upon cooling without any external load. Steel grades C45 (S 0.030 wt.%, no Mn and no Cr), S103 (Mn 0.25 wt.% and S 0.020 wt.% with no Cr), CK60 (0.75 wt.% Mn, 0.07 wt.% S and 0.15 wt.% Cr) and EN 1.4034 (Cr 12 wt.%, Mn 1.0 wt.% and S 0.035 wt.%) are studied under identical conditions using copper foils of 70-microns-thick. The samples were held above the melting point of copper at 1100 °C under high vacuum for different time durations (between 180 and 3600 s) and then cooled spontaneously. The joints were found cracked during cooling after a certain critical holding time. This critical holding time for cracking was found to decrease with increasing the Mn content and the S content of steel. It is observed that cracking is due to the precipitation of a critical amount of MnS phase upon cooling. The MnS/Cu interface is the weakest interface in the joint (with adhesion ensured only by van-der-Waals bonds), which is broken/separated upon cooling due to difference in heat expansion coefficients of the sulfide and copper phases. Higher is the Mn and S content, shorter is the probable time required for crack to appear in the joint. The braze integrity diagram is constructed as function of solubility product of MnS in steel and holding time showing a stable crack-free technological region and an unstable technological region with high probability of crack formation.

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