Fatigue Crack Growth Behaviour of High Strength Ferritic Steels in High Pressure Hydrogen (original) (raw)
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Engineering Fracture Mechanics, 2011
Experiments to investigate the effect of hydrogen pressure and test frequency on the fatigue crack growth properties of a Ni-Cr-Mo steel for the storage cylinder of a 70 MPa hydrogen storage station were conducted. Compact tension specimens were cut out from the storage cylinder. The crack growth properties obtained in hydrogen gas were compared with those obtained in air. Higher hydrogen pressures and lower loading frequencies lead to faster crack growth. However, there is an upper limit to the acceleration of the fatigue crack growth rate in hydrogen gas, which can be used for the design of the hydrogen cylinder. The effect of long and large inclusions present in the steel was also verified. The observations carried out on specimen fracture surfaces showed that the low population of inclusions did not influence the fatigue crack growth rate.
Fatigue crack growth modeling of pipeline steels in high pressure gaseous hydrogen
International Journal of Fatigue, 2014
This work proposes a phenomenological fatigue crack propagation (FCP) model for API-5L X100 pipeline steel exposed to high-pressure gaseous hydrogen. The semi-empirical model is predicated upon the hypothesis that one of two mechanisms dominate the fatigue crack growth (FCG) response depending upon the crack extension per cycle (da/dN) and the material hydrogen concentration. For da/dN between approximately 1 Â 10 À5 mm/cycle and 3 Â 10 À4 mm/cycle, fatigue crack growth in hydrogen is markedly increased over that in laboratory air, resulting in a Paris exponent over two and a half times that of air and producing a predominately intergranular crack propagation surface. Fatigue crack growth in hydrogen at da/dN above approximately 3 Â 10 À4 mm/cycle result in FCP rates over an order of magnitude higher than that of lab air. The Paris exponent in this regime approaches that of lab air and the crack morphology is predominately transgranular. Increasing the hydrogen test pressure from 1.7 MPa to 20.7 MPa increases the FCG rate by as much as two, depending upon the stress intensity factor. It is proposed that the FCG response in hydrogen at da/dN <3 Â 10 À4 mm/cycle is primarily affected by the hydrogen concentration within the fatigue process zone, resulting in a hydrogen-dominated mechanism, and that the FCG response in hydrogen at da/dN >3 Â 10 À4 mm/cycle results from fatigue-dominated mechanisms. The proposed model predicts fatigue crack propagation as a function of applied DK and hydrogen pressure. Results of fatigue crack growth tests in gaseous hydrogen as well as fracture morphology are presented in support of the proposed model. The model correlates well with test results and elucidates how the proposed mechanisms contribute to fatigue crack propagation in pipeline steel in environments similar to those found in service.
A study of fatigue crack propagation in prior hydrogen attacked pressure vessel steels
Metallurgical Transactions A, 1985
A study has been made of the effects of prior hydrogen attack damage on fatigue crack propagation behavior in commercial pressure vessel steels. Quenched and tempered Mn-Mo-Ni steel (ASTM A533B Class 2) and normalized and tempered 2.25Cr-lMo steel (ASTM A387 Class 2 Grade 22) were exposed to gaseous hydrogen atmospheres for up to 1480 hours at hydrogen pressures of 12.4 to 17.2 MPa and temperatures of 550 ° to 600 °C and tested in fatigue. Mild degrees of hydrogen damage, characterized by limited methane bubble formation with no appreciable decarburization, were found to increase growth rates slightly at near-threshold stress intensities. Severe degrees of hydrogen damage, characterized by extensive intergranular bubble formation and decarburization with associated large reductions in strength and toughness, were found to have no further influence on nearthreshold growth rates. The minor influence of prior hydrogen damage on fatigue crack extension, even for cases of severe attack, is attributed to result from two mutually competitive mechanisms, namely, the creation of methane-filled voids on prior austenite grain boundaries, which increases growth rates, and the enhancement in crack closure from decarburization-induced softening and rough cavitated intergranular fracture surfaces, which decreases growth rates.
Fatigue Crack Growth Under High Pressure of Gaseous Hydrogen: Experiments and Modeling
2014
In this study, the effect of gaseous hydrogen pressure in relation with the loading frequency on the fatigue crack growth behavior of a precipitation-hardened martensitic stainless steel is investigated. It is found that increasing the hydrogen pressure from 0.09 to 9 MPa induces an enhancement of the fatigue crack growth rates. This enhancement is pronounced particularly at higher stress intensity factor amplitudes at 9 MPa. Meanwhile, decreasing the frequency from 20 to 0.2 Hz under 0.9 MPa of hydrogen reveals a significant increase in the crack growth rates that tends to join the curve obtained under 9 MPa at 20 Hz, but with a different cracking mode. However, it is shown that the degradation in fatigue crack growth behavior derives from a complex interaction between the fatigue damage and the amount of hydrogen enriching the crack tip, which is dependent on the hydrogen pressure, loading frequency, and stress intensity factor level. Scanning electron microscope (SEM) observations of the fracture surfaces are used to support the explanations proposed to account for the observed phenomena.
Development of a Model for Hydrogen-Assisted Fatigue Crack Growth of Pipeline Steel 1
Journal of Pressure Vessel Technology
Hydrogen has been proposed as a potential partial solution to the need for a clean-energy economy. In order to make this a reality, large-scale hydrogen transportation networks need to be engineered and installed. Steel pipelines are the most likely candidate for the required hydrogen transportation network. One historical barrier to the use of steel pipelines to transport hydrogen was a lack of experimental data and models pertaining to the fatigue response of steels in gaseous hydrogen. Extensive research at NIST has been performed in conjunction with the ASME B31.12 Hydrogen Piping and Pipeline committee to fill this need. After a large number of fatigue crack growth (FCG) tests were performed in gaseous hydrogen, a phenomenological model was created to correlate the applied loading conditions, geometry, and hydrogen pressure to the resultant hydrogen-assisted fatigue crack growth (HA-FCG) response of the steels. As a result of this extensive data set, and a simplification of the...
Application of a Model of Hydrogen-Assisted Fatigue Crack Growth in 4130 Steel
2017
In this work, we applied a finite element model to predict the cyclic lifetime of 4130 steel cylinders under the influence of hydrogen. This example is used to demonstrate the efficacy of a fatigue crack growth (FCG) model we have developed. The model was designed to be robust and incorporate features of stress-assisted hydrogen diffusion, large-scale plasticity, hydrogen gas pressure, loading frequency, and effects of microstructure. The model was calibrated to the 4130 steel material by use of tensile tests and experimental FCG results of a compact tension specimen. We then used the model to predict the hydrogenassisted FCG rate and cycle life of a pressurized cylinder with a deliberate initial thumbnail crack. The results showed good correlation to the cyclic lifetime results of 4130 pressurized cylinders found in the literature.
Hydrogen enhanced fatigue in full scale metallic vessel tests – Results from the MATHRYCE project
International Journal of Hydrogen Energy, 2017
This study investigates the fatigue life of CreMo pressure vessels for hydrogen storage by hydraulic and hydrogen pressure cycle tests. Two different sized cylinders have been tested; 35 L inner volume and 28 MPa working pressure (WP) and 198 L volume and 41 MPa WP. On the inner surface of the cylinders U-shaped notches of different depths were machined by electro discharge machining technique. The initial notch sizes were designed based on a two stage fatigue predictive model based on fracture mechanics to develop through wall cracks in the deepest notches after about 50,000 hydraulic cycles together with crack propagation of the intermediate notches and crack initiation in the smallest. The cylinders were cycled between the nominal pressure of 2 MPa and the WP until leak before break (LBB). Strain gauges were placed at the external surface of the cylinders in correspondence of the internally machined notches. On the notches which developed through wall, the strain showed a progressive decrease followed by an increase of the hoop strain during the final stage of crack propagation until LBB failure. Hydrogen effect was clearly identified by the reduction in the number of cycles to failure comparing tests in hydrogen and in oil. Subsequent failure analysis at the end of each test revealed a typical trans-granular fatigue crack surface morphology (with fatigue striations) for tests in oil, while quasi cleavage and intergranular fracture appearance were found for hydrogen tests.