Characterisation of the corrosion fatigue behaviour of brazed AISI 304L/BNi-2 joints in synthetic exhaust gas condensate

Schmiedt, Anke; Manka, M.; Tillmann, Wolfgang; Walther, Frank

doi:10.1007/s40194-018-0557-y

Cited by 10 publications

(22 citation statements)

References 18 publications

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“…The determined directional accumulation of plastic strain is a result of an asymmetric cyclic loading with mean stresses and is well known as ratcheting fatigue. The ratcheting strains in form of the total maximum strain max,t and the total mean strain m,t, respectively, are known to be more pronounced for elevated mean stresses and stress amplitudes [11]. The degressive trend of the cyclic deformation curves within the constant stress levels corresponds well with results in the literature on the AISI 304L austenite [12].…”

Section: Fatigue Behavioursupporting

confidence: 84%

“…The tests were performed by applying a stress ratio of R = 0.1 and a frequency of f = 10 Hz, using sinusoidal load time functions. In addition to constant amplitude tests (CAT) with a limited number of cycles N = 2·10 6 , a time-and source-efficient procedure, based on stepwise load increase tests, was applied, which is already established for a wide range of material classes and joints [10,11]. With a constant stress ratio, the maximum stress was increased stepwise by max = 10 MPa each N = 10 4 cycles, starting at a stress level of 50 MPa at which the material and joints are expected to be damage-free up to the level of specimen`s failure.…”

Section: Methodsmentioning

confidence: 99%

“…Within LIT, the transition from almost steady to significantly deviating material reactions at max,e (LIT) as well as the failure maximum stress max,f (LIT) have proven to be characteristic for the fatigue behaviour of various materials and joints [10,11]. For metastable austenitic materials, a particular evaluation method of LIT was recommended in the literature [6].…”

Section: Methodsmentioning

confidence: 99%

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Tensile and fatigue assessments of brazed stainless steel joints using digital image correlation

et al. 2018

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Abstract. For mechanical tests of brazed stainless steel joints, the local deformation behaviour within the small area of the brazing seam is a major concern, because local strains cannot be detected with standard mechanical extensometers. The current study allows a fundamental comprehension of the gauge length influence on the strain measurements of brazed joints with smooth and notch-containing surfaces, under quasistatic and cyclic loadings. Therefore, the optical measurement technique of digital image correlation (DIC) is used within tensile and fatigue tests of brazed AISI 304L/BAu-4 joints in an as-received and pre-corroded condition. A triggered image acquisition of the DIC system is successfully applied to evaluate the local ratcheting fatigue behaviour in the area of the brazing seam at a frequency of 10 Hz. The gauge length influence, analysed in the range of 0.5 to 12.5 mm, is more pronounced with increasing tensile and fatigue stresses and is significantly enhanced for notch-containing surfaces. Instrumented load increase tests with strain, electrical, magnetic and temperature measuring techniques have proven to be appropriate to estimate fatigue properties of the brazed joints with a deviation of 4%. Fatigue and corrosion fatigue damage mechanisms are evaluated by using scanning electron microscopy with secondary and back-scattered electron detectors.

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Section: Fatigue Behavioursupporting

confidence: 84%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Tensile and fatigue assessments of brazed stainless steel joints using digital image correlation

et al. 2018

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“…The brazed joints are additionally fatigued in air after pre‐corrosions, in order to evaluate the effect of a long‐time corrosion. In previous works of the authors, several results concerning the fatigue and corrosion fatigue behaviour of brazed AISI 304L/BNi‐2 joints with a limiting number of cycles N limit = 2·10 6 have been published . In the current study, the frequency‐dependent fatigue and corrosion fatigue behaviours are investigated, damage mechanisms are identified and the fatigue strength at 2·10 7 cycles is evaluated statistically.…”

Section: Introductionmentioning

confidence: 95%

“…A commercially available nickel‐based brazing alloy BNi‐2 (Ni 620) with the chemical composition Ni‐7Cr‐4.5Si‐3.2B‐3Fe was applied as a 50‐ μm amorphous brazing foil between the base material prior to the brazing. The brazing process was carried out in a vacuum furnace with a vacuum in the range of 1·10 −5 to 8·10 −5 mbar, at a temperature of 1050°C and with a dwell time of 2 minutes . To prevent the formation of brittle phase bands in the centre of the seam, a heating rate of 50 K/min was applied in combination with a short dwell time (Figure A) .…”

Section: Materials and Materials Conditionsmentioning

confidence: 99%

Frequency‐dependent fatigue and corrosion fatigue assessment of brazed AISI 304L/BNi‐2 joints in air and synthetic exhaust gas condensate

Schmiedt

Lücker

Manka

et al. 2018

Fatigue Fract Eng Mat Struct

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Since brazed components are often cyclically loaded in corrosive environments, the corrosion fatigue behaviour of the joints has to be investigated. Fatigue tests of brazed AISI 304L/BNi‐2 joints, relevant for exhaust gas heat exchangers, were performed with specimens in the as‐received condition and after pre‐corrosion according to VDA 230‐214. Additionally, the superimposed corrosion fatigue loading in an exhaust gas condensate was realised using a corrosion cell. Corrosion‐induced and deformation‐induced microstructural changes were metallographically evaluated. The influence of the test frequency from 1 to 150 Hz on the cyclic deformation and damage behaviour was characterised. In a statistical analysis, the fatigue strength of 210 MPa at 2·107 cycles was determined for the as‐received condition with a 50% failure probability. The pre‐corrosion as well as the superimposed loading lead to a reduction of the fatigue strength down to 22%. A novel test strategy is suitable for precise fatigue and corrosion fatigue assessments.

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Fatigue of brazed joints made of X5CrNi18-10 and Cu110 and derivation of reliable assessment approaches

et al. 2020

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Brazing in a continuous belt furnace is a quite cost-effective way of joining components consisting of many individual parts. It is extensively used in many industrial sectors like the automotive or in the energy industry. Even though many components are cyclically loaded during service up to now, no approaches to assess the lifetime under in-service loads are available. In order to assess the fatigue strength of brazed joints, three different specimen types have been investigated: peel and shear as well as a component-like specimens. The specimens were characterized and tested under load control using constant and variable amplitudes. Subsequently, the fatigue life of these joints was assessed by linear-elastic notch stresses. A reference S-N curve and characteristic damage sums were derived that enable to perform a reliable fatigue assessment. Further parameters which seem to have a strong influence on the fatigue life, the surface topology, and the overall quality of the braze were identified. Their influence is discussed.

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Characterisation of the corrosion fatigue behaviour of brazed AISI 304L/BNi-2 joints in synthetic exhaust gas condensate

Cited by 10 publications

References 18 publications

Tensile and fatigue assessments of brazed stainless steel joints using digital image correlation

Tensile and fatigue assessments of brazed stainless steel joints using digital image correlation

Frequency‐dependent fatigue and corrosion fatigue assessment of brazed AISI 304L/BNi‐2 joints in air and synthetic exhaust gas condensate

Fatigue of brazed joints made of X5CrNi18-10 and Cu110 and derivation of reliable assessment approaches

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