Tensile and Fatigue Behavior of an Austenitic Stainless CrNi-Steel at 10 MPa Hydrogen Gas Atmosphere

2017 ◽  
Author(s):  
Martina Schwarz ◽  
Erich Sattler ◽  
Stefan Zickler ◽  
Stefan Weihe
Keyword(s):  
Hydrogen Embrittlement ◽  
Ambient Temperature ◽  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Nickel Content ◽  
Hydrogen Gas ◽  
Material Behavior ◽  
Relative Reduction ◽  
Nominal Composition ◽  
Gas Atmosphere

To understand the role of nickel in austenitic stainless steels, six heats were produced from one nominal composition differing in the nickel content between 9 % and 13 %. To characterize the material behavior in hydrogen gas atmosphere at 10 MPa, tensile and fatigue testing was conducted at ambient temperature and at 223 K. The susceptibility to hydrogen embrittlement clearly decreases with increasing nickel content both at ambient temperature and at 223 K. But at low temperature the relative reduction of area is less and thus hydrogen embrittlement is intensified. Fatigue tests confirmed these results as the reduction of the fatigue life is strongly dependent on the nickel content and the temperature. The influence of the test frequency was investigated at 4 different frequency levels. A low frequency slightly increases the susceptibility to hydrogen embrittlement. To gain a better understanding of hydrogen embrittlement and its influences the crack growth behavior was analyzed in detail.

scholarly journals Hydrogen effect on the fatigue behavior of LBM Inconel 718

2018 ◽  
Vol 165 ◽  
pp. 02010 ◽  
Author(s):  
Simon Puydebois ◽  
Abdelali Oudriss ◽  
Pierre Bernard ◽  
Laurent Briottet ◽  
Xavier Feaugas
Keyword(s):  
Hydrogen Embrittlement ◽  
Fracture Surface ◽  
Inconel 718 ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Ion Beam ◽  
Hydrogen Gas ◽  
Hydrogen Effect ◽  
Cycle Number ◽  
The Impact

For several years, Inconel 718 made by Laser Beam Melting (LBM) has been used for components of the Ariane propulsion systems manufactured by ArianeGroup. In the aerospace field, many components of space engines are used under hydrogen environment. The risk of hydrogen embrittlement (HE) can be therefore a first order problem. Consequently, to improve the HE sensitivity of LBM Inconel 718, a systematic approach needs to be developed to characterize the microstructure at different scales and its interaction with hydrogen. This study addresses the impact of gaseous hydrogen on the material mechanical behavior under fatigue loadings. In a first step, the low cycle fatigue behavior under 300 bar of hydrogen gas has been evaluated with specimen loaded at a constant load ratio of R=0.1 and a frequency of 0.5 Hz. A reduction in the cycle number of fracture is shown. This reduction of fatigue life is a consequence of the impact of hydrogen damage processes. The impact of hydrogen is evaluated at the stages of crack initiation, crack propagation. These results are discussed in relation with the hydrogen embrittlement mechanisms and particularly in terms of hydrogen / plasticity interactions. To achieve this, the fracture surface morphology was first examined using scanning electron microscopy and second samples near the fracture surface were extracted using Focused-Ion Beam machining from regions containing striation. The main result observed is a reduction of the size of dislocation organization in relation with a decrease of the striation distance.

A Numerical and Experimental Study of the Disk Pressure Test

2013 ◽  
Author(s):  
Kevin Ardon ◽  
Yann Charles ◽  
Monique Gaspérini ◽  
Jader Furtado
Keyword(s):  
Finite Element ◽  
Hydrogen Embrittlement ◽  
Hydrogen Gas ◽  
Material Behavior ◽  
Experimental Investigations ◽  
Cohesive Elements ◽  
Global Response ◽  
Lower Face ◽  
Neutral Gas ◽  
Pressure Test

The Disk Pressure Test is used to select metallic materials for hydrogen storage and transportation and consists of a thin metallic disk bulged out until fracture by applying a gas pressure on its lower face. The ratio of the fracture pressures obtained with a neutral gas and with hydrogen gas defines a phenomenological index for material hydrogen sensitivity. In order to use the Disk Pressure Test for the selection of materials exposed at high pressure (50–70 MPa), a thorough study of this method has been carried out. Experimental investigations of damage mechanisms at different scales and finite element computations of the test have been carried out to exhibit the main features of hydrogen embrittlement in low alloy Fe-Cr-Mo tempered steels during the disk rupture test. Finite Element computations of the test permitted to predict the global response and to understand the effect of boundary conditions and of material behavior on stress gradients and plastic strain distribution throughout the disk. Using hydrogen sensitive cohesive elements to model the global crack path, good agreement with experiment was obtained on the effect of disk thickness and of hydrogen pressure rate on the failure pressure. The relative influence of loading conditions and material behavior on the hydrogen embrittlement during the disk rupture test are discussed.

Fatigue of Unidirectional Cord-Rubber Composites

1999 ◽  
Vol 27 (1) ◽  
pp. 48-57 ◽  
Author(s):  
Y. Liu ◽  
Z. Wan ◽  
Z. Tian ◽  
X. Du ◽  
J. Jiang ◽  
...  
Keyword(s):  
Damage Accumulation ◽  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Constant Load ◽  
Testing System ◽  
Rubber Composites ◽  
Cycle Frequency ◽  
Periodic Loading ◽  
Fatigue Damage Accumulation ◽  
Rubber Composite

Abstract A fatigue testing system is established with which the real-time recording of stress, strain, temperature, and hysteresis loss of rubbers or cord-rubber composite specimens subjected to periodic loading or extension can be successfully carried out. Several problems are connected with the experimental study of the fatigue of rubber composites. In constant extension cycling, the specimen becomes relaxed because of the viscoelasticity of rubber composites, and the imposed tension-tension deformation becomes complex. In this method, the specimen is unlikely to fail unless the imposed extensions are very large. Constant load cycling can avoid the shortcomings of constant extension cycling. The specially designed clamps ensure that the specimen does not slip when the load retains a constant value. The Deformation and fatigue damage accumulation processes of rubber composites under periodic loading are also examined. Obviously, the effect of cycle frequency on the fatigue life of rubber composites can not be ignored because of the viscoelasticity of constituent materials. The increase of specimen surface temperature is relatively small in the case of 1 Hz, but the temperature can easily reach 100°C at the 8 Hz frequency. A method for evaluating the fatigue behavior of tires is proposed.

Infrared Spectroscopy of Molten LiCl−KCl under Hydrogen Gas Atmosphere

2004 ◽  
Vol 108 (21) ◽  
pp. 4567-4569 ◽  
Author(s):  
Hironori Nakajima ◽  
Toshiyuki Nohira ◽  
Yasuhiko Ito
Keyword(s):  
Infrared Spectroscopy ◽  
Hydrogen Gas ◽  
Gas Atmosphere

Partial Devitrification of Sintered Silicon Nitride During Static Fatigue Testing

1992 ◽  
Vol 287 ◽  
Author(s):  
W. Braue ◽  
G. D. Quinn
Keyword(s):  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Slow Crack Growth ◽  
Stress Rupture ◽  
Secondary Phase ◽  
Boundary Phase ◽  
Static Fatigue ◽  
Phase Assemblage ◽  
Transmission Electron ◽  
Stress States

ABSTRACTThe static fatigue behavior of sintered Y2O3/A12O3-fluxed Si3N4 in air is controlled by slow crack growth or creep fracture. Partial devitrification of the amorphous grain boundary phase at 1000°C and 1100°C improves the static fatigue resistance with specimens surviving up to 1500 hrs. during stress rupture experiments. In this study the early stages of partial devitrification during static fatigue testing at 1000°C are investigated by conventional and analytical transmission electron microscopy with emphasis on nucleation and growth of δ-Y2Si2O7 and X1-Y2SiO5 and possible constraints from different stress states. The results show that the stress state does not affect the nature of the secondary phase assemblage. However, the amount of crystallization is higher within the tensile region of the flexural specimens than in areas which experienced compressive stresses.

Gigacycle Fatigue of Welded Joints of Structural Materials (A Review)

2016 ◽  
Vol 17 ◽  
pp. 14-30 ◽  
Author(s):  
Okechukwu P. Nwachukwu ◽  
Alexander V. Gridasov ◽  
Ekaterina A. Gridasova
Keyword(s):  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Testing Machine ◽  
Structural Materials ◽  
Fatigue Tests ◽  
Material Defects ◽  
Graphite Cast Iron ◽  
Ultrasonic Fatigue ◽  
Materials Used ◽  
Fatigue Failures

This review looks into the state of gigacycle fatigue behavior of some structural materials used in engineering works. Particular attention is given to the use of ultrasonic fatigue testing machine (USF-2000) due to its important role in conducting gigacycle fatigue tests. Gigacycle fatigue behavior of most materials used for very long life engineering applications is reviewed.Gigacycle fatigue behavior of magnesium alloys, aluminum alloys, titanium alloys, spheroid graphite cast iron, steels and nickel alloys are reviewed together with the examination of the most common material defects that initiate gigacycle fatigue failures in these materials. In addition, the stage-by-stage fatigue crack developments in the gigacycle regime are reviewed. This review is concluded by suggesting the directions for future works in gigacycle fatigue.

scholarly journals Stacking Fault Energy in Relation to Hydrogen Environment Embrittlement of Metastable Austenitic Stainless CrNi-Steels

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1170
Author(s):  
Robert Fussik ◽  
Gero Egels ◽  
Werner Theisen ◽  
Sebastian Weber
Keyword(s):  
Phase Transformation ◽  
Intermediate Stage ◽  
Tensile Tests ◽  
Stacking Fault ◽  
Hydrogen Gas ◽  
Stacking Fault Energy ◽  
Austenitic Steels ◽  
Aisi 304L ◽  
Hydrogen Environment ◽  
Gas Atmosphere

Metastable austenitic steels react to plastic deformation with a thermally and/or mechanically induced martensitic phase transformation. The martensitic transformation to α’-martensite can take place directly or indirectly via the intermediate stage of ε-martensite from the single-phase austenite. This effect is influenced by the stacking fault energy (SFE) of austenitic steels. An SFE < 20 mJ/m2 is known to promote indirect conversion, while an SFE > 20 mJ/m2 promotes the direct conversion of austenite into α’-martensite. This relationship has thus far not been considered in relation to the hydrogen environment embrittlement (HEE) of metastable austenitic CrNi steels. To gain new insights into HEE under consideration of the SFE and martensite formation of metastable CrNi steels, tensile tests were carried out in this study at room temperature in an air environment and in a hydrogen gas atmosphere with a pressure of p = 10 MPa. These tests were conducted on a conventionally produced alloy AISI 304L and a laboratory-scale modification of this alloy. In terms of metal physics, the steels under consideration differed in the value of the experimentally determined SFE. The SFE of the AISI 304L was 22.7 ± 0.8 mJ/m2 and the SFE of the 304 mod alloy was 18.7 ± 0.4 mJ/m2. The tensile specimens tested in air revealed a direct γàα’ conversion for AISI 304L and an indirect γàεàα’ conversion for 304mod. From the results it could be deduced that the indirect phase transformation is responsible for a significant increase in the content of deformation-induced α’-martensite due to a reduction of the SFE value below 20 mJ/m2 in hydrogen gas atmosphere.

As-Built Geometry and Surface Finish Effects on Fatigue and Tensile Properties of Laser Fused Titanium 6Al-4V

2017 ◽  
Author(s):  
Onome Scott-Emuakpor ◽  
Tommy George ◽  
Emily Henry ◽  
Casey Holycross ◽  
Jeff Brown
Keyword(s):  
Tensile Properties ◽  
Surface Finish ◽  
Fatigue Behavior ◽  
Turbine Blades ◽  
Material Behavior ◽  
Small Scale ◽  
Internal Cooling ◽  
Roughness Effects ◽  
Form And Function ◽  
And Function

The as-built material behavior of additive manufactured (AM) Titanium (Ti) 6Al-4V is investigated in this study. A solution heat treated, aged, stress relieved, and hot isostatic pressed Laser Powder Bed Fusion (LPBF) AM process was used to manufacture the specimens of interest. The motivation behind this work is based on the ever-growing desire of aerospace system designers to use AM to fabricate components with novel geometries. Specifically, there is keen interest in AM components with complex internal cooling configurations such as turbine blades, nozzle vanes, and heat exchangers that can improve small scale propulsion performance. Though it is feasible to three-dimensionally print parts that meet the Fit portion of a part characteristic description and identification, the Form and Function portions have proven to be more difficult to conquer. This study addresses both the Form and Function characteristics of the LPBF AM process via the investigation of geometry variation and surface roughness effects pertaining to mechanical properties and fatigue behavior of Ti 6Al-4V. Results show that geometry variation may be the cause of increased vibration fatigue life uncertainty. Also, both fatigue and tensile properties show profound discrepancies associated with surface finish. As-built surface finish specimens have lower fatigue and ductility performance, but the results are more consistent than polished data.

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