Reduced strength degradation of reactive air brazed Ba05Sr05Co08Fe02O3-δ membranes by pre-oxidation of metallic components

Herzog, Simone; Kaletsch, Anke; Broeckmann, Christoph

doi:10.1016/j.msea.2022.143993

Cited by 3 publications

(18 citation statements)

References 34 publications

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“…Bars made of the heat-resistant austenitic steel AISI 314 (DIN X15CrNiSi25-21, EN 1.4841) were coated with different variants. As a reference condition, we refer to results published in [ 39 ] where blank AISI 314 was brazed to BSCF without any diffusion barrier. Aluminizing was carried out by solid-state diffusion in the pack cementation process at Chromin Maastricht BV, Maastricht, The Netherlands.…”

Section: Methodsmentioning

confidence: 99%

“…The brazing of the joints was conducted after the vertical arrangement of all components in a specially constructed brazing frame; see Figure 1 a,b. Details regarding the brazing frame are given in [ 39 ]. The programmed temperature–time regime of a brazing cycle is given in Table 2 .…”

Section: Methodsmentioning

confidence: 99%

“…Suitable metallic joining partners show a similar thermal expansion to the ceramic OTM. Examples include ferritic steels such as Kanthal [ 35 ], Crofer APU or H [ 36 ], AISI 430 [ 37 ], AISI 446 [ 38 ], austenitic heat-resistant steels such as AISI 310S [ 33 ], AISI 314 [ 39 ], and nickel-base alloys such as alloy 602 CA [ 40 ], Haynes 214 [ 35 ], or Inconel 600 [ 33 ].…”

Section: Introductionmentioning

confidence: 99%

“…After 1500 h of Al aging at 850 °C, no growing reaction layers were observed in cross-sections. In [ 39 ], we demonstrated how a pre-oxidation of AISI 314 at 1050 °C can reduce the strength degradation of BSCF-Ag-3CuO-AISI 314 joints after 1000 h of isothermal aging at 850 °C. Without pre-oxidation, the characteristic joint strength decreases from 81 MPa immediately after brazing to 17 MPa after 1000 h, and chromium poisoning is present.…”

Section: Introductionmentioning

confidence: 99%

“…However, there are no heat-resistant austenitic steels with sufficiently high Al content [ 48 ], since these would form intermetallic phases during cooling. The choice of a ferritic high-Al steel led to cracking due to the large differences in thermal expansion coefficients [ 39 ]. In the present study, therefore, aluminum-containing coatings or diffusion layers were applied onto the metallic joining partner before brazing to BSCF and aging.…”

Section: Introductionmentioning

confidence: 99%

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Diffusion Barriers Minimizing the Strength Degradation of Reactive Air Brazed Ba0.5Sr0.5Co0.8Fe0.2O3-δ Membranes during Aging

2023

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The separation of oxygen from air by means of inorganic ceramic membranes requires gas-tight ceramic–metal joints that enable reliable permeation operation in the oxygen partial pressure gradient at 850 °C. Reactive air brazing is a promising method to solve this challenge. However, reactive air brazed BSCF membranes suffer from a significant strength degradation that is caused by unhindered diffusion from the metal component during aging. In this study, we investigated how diffusion layers applied on the austenitic steel AISI 314 influence the bending strength of BSCF-Ag3CuO-AISI314 joints after aging. Three different approaches were compared as diffusion barriers: (1) aluminizing via pack cementation, (2) spray coating with NiCoCrAlReY, and (3) spray coating with NiCoCrAlReY and an additional 7YSZ top layer. Coated steel components were brazed to bending bars and aged for 1000 h at 850 °C in air prior to four-point bending and subsequent macroscopic as well microscopic analyses. In particular, coating with NiCoCrAlReY showed low-defect microstructures. The characteristic joint strength was raised from 17 MPa to 35 MPa after 1000 h aging at 850 °C. In addition, the dominant delamination fracture between the steel and the mixed oxide layer, observed in the reference series with uncoated steel, could be replaced by mixed and ceramic fractures of higher strength. The effect of residual joint stresses on the crack formation and path is analyzed and discussed. Chromium poisoning could no longer be detected in the BSCF, and interdiffusion through the braze was effectively reduced. Since the strength degradation of reactive air brazed joints is mainly caused by the metallic joining partner, the findings on the effect of the diffusion barriers in BSCF joints might be transferred to numerous other joining systems.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Diffusion Barriers Minimizing the Strength Degradation of Reactive Air Brazed Ba0.5Sr0.5Co0.8Fe0.2O3-δ Membranes during Aging

2023

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Review of reactive air brazing: fundamental, progress, and perspective

Si,

Wang,

Guo

et al. 2024

Materials & Design

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Failure Mechanisms of Ba0.5Sr0.5Co0.8Fe0.2O3−δ Membranes after Pilot Module Operation

et al. 2022

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The step from the testing of oxygen transport membranes on a lab scale to long-term operation on a large scale is a challenge. In a previous study, membrane failure was observed at defined positions of one end of the cooled tubular Ba0.5Sr0.5Co0.8Fe0.2O3−δ membranes after an emergency shutdown. To understand the failure mechanisms, strength degradation and transient stress distribution were investigated by brittle-ring tests and finite element simulations, respectively. A 15% decrease in the characteristic strength of 162 MPa was proven after aging at 850 °C and was attributed to grain coarsening. The reduction in characteristic strength after thermal shock ranged from 5 to 90% depending on the cooling rates, and from 5 to 40% after the first and 20th soft thermal cycling. Simulations indicated the chemical strains induced by a 10-bar feed air and 50 mbar permeate pressure, which caused tensile stresses of up to 70 MPa at the outer surface. These stresses relaxed to 43 MPa by creep within a 1000 h operation. A remaining local stress maximum seemed to be responsible for the fracture. It evolved near the experimentally observed fracture position during a 1000 h permeation and exceeded the temperature and time-dependent strength. The maximum stress was formed by a chemical strain at temperatures above 500 °C but effective creep relaxation needed temperatures above 750 °C.

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Reduced strength degradation of reactive air brazed Ba05Sr05Co08Fe02O3-δ membranes by pre-oxidation of metallic components

Cited by 3 publications

References 34 publications

Diffusion Barriers Minimizing the Strength Degradation of Reactive Air Brazed Ba0.5Sr0.5Co0.8Fe0.2O3-δ Membranes during Aging

Diffusion Barriers Minimizing the Strength Degradation of Reactive Air Brazed Ba0.5Sr0.5Co0.8Fe0.2O3-δ Membranes during Aging

Review of reactive air brazing: fundamental, progress, and perspective

Failure Mechanisms of Ba0.5Sr0.5Co0.8Fe0.2O3−δ Membranes after Pilot Module Operation

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