Corrosion Fatigue Performance of Duplex 2507 for Riser Applications

2010 ◽  
Author(s):  
Feng Gui ◽  
Ramgopal Thodla ◽  
Ken Evans ◽  
Carlos Joia ◽  
Ilson Palmieri Baptista
Keyword(s):  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Crack Growth ◽  
Corrosion Fatigue ◽  
Growth Rates ◽  
High Strength Steels ◽  
High Strength ◽  
Fatigue Performance ◽  
Partial Pressures ◽  
Crack Growth Rates

Corrosion fatigue performance is of interest for high strength steels in riser applications. This work investigated the corrosion fatigue performance of 2507 duplex stainless steel for use as riser materials in environments containing high partial pressures of carbon dioxide (50–100 bar) and limited quantity of hydrogen sulfide (0–0.12 bar). The procedures developed for controlling oxygen and Fe2+ contamination as well as methods to evaluate the concentration of H2S in the autoclave are presented. The crack growth rates and ΔKth for these materials in the pressure environments were discussed along with procedures to obtain ΔKth, when they were below 5ksi√in. Low crack growth rates in the range of 1×10−8 in/cycle were measured and the effect of sour environments was quantified. The fatigue crack growth rate in sour environments on 2507 duplex stainless steel is a 10x higher than in air.

scholarly journals Effects of Waveform and Cycle Period on Corrosion-Fatigue Crack Growth in Cathodically Protected High-Strength Steels

2014 ◽  
Vol 891-892 ◽  
pp. 211-216 ◽  
Author(s):  
Mark Knop ◽  
Nick Birbilis ◽  
Stan Lynch
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Corrosion Fatigue ◽  
Growth Rates ◽  
High Strength Steels ◽  
High Strength ◽  
Corrosion Fatigue Crack ◽  
Corrosion Fatigue Crack Growth ◽  
Crack Growth Rates

The processes involved in corrosion fatigue in general are briefly outlined, followed by a brief review of recent studies on the effects of cycle frequency (rise times) and electrode potential on crack-growth rates at intermediate ΔK levels for cathodically protected high-strength steels. New studies concerning the effects of fall times and hold times at maximum and minimum loads on crack-growth rates (for Kmax values below the sustained-load SCC threshold) are presented and discussed. Fractographic observations and the data indicate that corrosion-fatigue crack-growth rates in aqueous environments depend on the concentration of hydrogen adsorbed at crack tips and at tips of nanovoids ahead of cracks. Potential-dependent electrochemical reaction rates, crack-tip strain rates, and hydrogen transport to nanovoids are therefore critical parameters. The observations are best explained by an adsorption-induced dislocation-emission (AIDE) mechanism of hydrogen embrittlement.

Corrosion-Fatigue Performance of High-Strength Riser Steels in Seawater and Sour Brine Environments

2011 ◽  
Author(s):  
Stephen J. Hudak ◽  
Guadalupe B. Robledo ◽  
Jeffrey Hawk
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Corrosion Fatigue ◽  
Cathodic Protection ◽  
High Strength Steels ◽  
High Strength ◽  
Fatigue Performance ◽  
Material Strength ◽  
Loading Frequency

Although new high-strength steels have recently been developed to meet the demands of increased reservoir pressures, and sour production fluids, the corrosion-fatigue performance of these new higher-strength materials is largely unknown. The goal of this study was to fill this knowledge gap by generating corrosion-fatigue data in two aggressive environments: 1) a sour production brine, and 2) seawater with cathodic protection. The focus of the current paper is on stress-life (S-N) corrosion-fatigue results in these environments, as well as a baseline air environment. Experiments were performed on five different steels with yield strengths ranging from 848 MPa to 1080 MPa. Prior frequency-scan results based on corrosion-fatigue crack growth rate data demonstrated that not all of these material-environment combinations exhibit a saturation frequency where the detrimental environmental effect approached a constant value as the cyclic loading frequency is decreased. Consequently, S-N tests were performed at different frequencies (0.01 Hz, 0.17 Hz, and 1 Hz), depending on the fatigue life regime, in attempting to match the loading frequencies experienced in service. Corrosion-fatigue occurred at stresses well below the fatigue endurance limit in laboratory air, and cyclic lives in the seawater with cathodic protection environment were found to be 2X to 10X less than those in the baseline air environment, while cyclic lives in the sour brine environment were found to be 30X to 100X less than those in the baseline air environment. In both environments, degradation was greatest at lower stresses in the high cycle fatigue regime. The effect of material strength level had little or no measurable effect on the S-N corrosion-fatigue performance, and the effect of cyclic frequency on the corrosion-fatigue performance was mixed. The S-N response to these two variables differed significantly from recently measured fatigue crack growth kinetics in these same materials that were performed in a companion study. Possible reasons for these differences are discussed.

The Effect of Cyclic Loading Frequency on Corrosion-Fatigue Crack Growth in High-Strength Riser Materials

2010 ◽  
Author(s):  
Stephen J. Hudak ◽  
James H. Feiger ◽  
Jason A. Patton
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Corrosion Fatigue ◽  
Growth Rates ◽  
High Strength ◽  
Loading Frequency ◽  
Corrosion Fatigue Crack ◽  
Corrosion Fatigue Crack Growth ◽  
Crack Growth Rates

Corrosion-fatigue is a significant design consideration in deepwater floating production systems. Mechanical loading is accentuated due to the compliant nature of these structures, and sour service conditions can also occur either due to the nature of the crude production or due to seawater flooding of the reservoir to enhance production yield. New high-strength riser steels have recently been developed to meet the demands of deepwater development. The objective of this study was to characterize the corrosion-fatigue resistance of these materials in terms of crack growth rates as a function of applied stress intensity factor range (ΔK), as well as cyclic loading frequency. Experiments were performed on five different steels with yield strengths ranging from 848 to 1080 MPa. Two environments were considered: seawater with cathodic protection to simulate the environment outside of the riser, and a sour brine environment with low oxygen (< 10 ppb) to simulate the environment inside the riser. Not all steels were tested in the sour brine environment since not all were designed to operate in sour service. For both environments, higher strength steels were found to exhibit higher growth rates and lower saturation frequencies. Fatigue crack growth rates as a function of ΔK were also measured, and exhibited two different frequency responses. At high ΔK, the classical frequency response occurred: decreased frequency gave increased crack growth rates. At low ΔK, an inverse frequency effect was observed: deceased frequency gave decreased crack growth rates, as well as increased corrosion-fatigue crack growth thresholds. These differences are believed to be caused by different underlying processes controlling crack growth — specifically, material-environment reaction kinetics at high ΔK, and crack closure due to corrosion-product wedging at low ΔK. The practical significance of these results is discussed, including selection of frequencies for corrosion-fatigue crack growth testing, and applicability of results to structural integrity assessments.

Fatigue Crack Growth of Duplex Stainless Steel Castings at 4 K

1985 ◽  
Vol 107 (2) ◽  
pp. 161-165 ◽  
Author(s):  
P. T. Purtscher ◽  
Y. W. Cheng ◽  
P. N. Li
Keyword(s):  
Stainless Steel ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Duplex Stainless Steel ◽  
Crack Growth ◽  
Growth Rates ◽  
Constant Load ◽  
Steel Castings ◽  
Constant Load Amplitude ◽  
Crack Growth Rates

Constant-load-amplitude stage II fatigue crack growth rates at 4 K were measured for duplex stainless steel castings. The results show that at a ΔK of 60 MPa•m1/2, da/dN = 7.6 × 10−4 mm/cycle for an alloy with 1 percent ferrite. For an alloy with 8 percent ferrite, da/dN is 35 percent, and for an alloy with 29 percent ferrite, da/dN is 260 percent greater than for the 1 percent ferrite alloy. However, the exponent in the Paris equation does not change appreciably (less than 18 percent) as the ferrite content changes from 1 to 29 percent.

Crack Growth in Stainless Steel 304 under Creep-Fatigue Loading

2007 ◽  
Vol 353-358 ◽  
pp. 485-490 ◽  
Author(s):  
Y.M. Baik ◽  
K.S. Kim
Keyword(s):  
Stress Intensity Factor ◽  
Stainless Steel ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Growth ◽  
Growth Rates ◽  
Static Loading ◽  
Fatigue Loading ◽  
Creep Fatigue ◽  
Crack Growth Rates

Crack growth in compact specimens of type 304 stainless steel is studied at 538oC. Loading conditions include pure fatigue loading, static loading and fatigue loading with hold time. Crack growth rates are correlated with the stress intensity factor. A finite element analysis is performed to understand the crack tip field under creep-fatigue loading. It is found that fatigue loading interrupts stress relaxation around the crack tip and cause stress reinstatement, thereby accelerating crack growth compared with pure static loading. An effort is made to model crack growth rates under combined influence of creep and fatigue loading. The correlation with the stress intensity factor is found better when da/dt is used instead of da/dN. Both the linear summation rule and the dominant damage rule overestimate crack growth rates under creep-fatigue loading. A model is proposed to better correlate crack growth rates under creep-fatigue loading: 1 c f da da da dt dt dt Ψ −Ψ     =         , where Ψ is an exponent determined from damage under pure fatigue loading and pure creep loading. This model correlates crack growth rates for relatively small loads and low stress intensity factors. However, correlation becomes poor as the crack growth rate becomes large under a high level of load.

Use of Duplex Stainless Steel in Economic Design of a Pressure Vessel

2006 ◽  
Vol 129 (1) ◽  
pp. 155-161 ◽  
Author(s):  
Milan Veljkovic ◽  
Jonas Gozzi
Keyword(s):  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Stainless Steels ◽  
Pressure Vessel ◽  
Design Procedure ◽  
High Strength Steels ◽  
High Strength ◽  
Pressure Vessels ◽  
Economic Design ◽  
European Standard

Pressure vessels have been used for a long time in various applications in oil, chemical, nuclear, and power industries. Although high-strength steels have been available in the last three decades, there are still some provisions in design codes that preclude a full exploitation of its properties. This was recognized by the European Equipment Industry and an initiative to improve economy and safe use of high-strength steels in the pressure vessel design was expressed in the evaluation report (Szusdziara, S., and McAllista, S., EPERC Report No. (97)005, Nov. 11, 1997). Duplex stainless steel (DSS) has a mixed structure which consists of ferrite and austenite stainless steels, with austenite between 40% and 60%. The current version of the European standard for unfired pressure vessels EN 13445:2002 contains an innovative design procedure based on Finite Element Analysis (FEA), called Design by Analysis-Direct Route (DBA-DR). According to EN 13445:2002 duplex stainless steels should be designed as a ferritic stainless steels. Such statement seems to penalize the DSS grades for the use in unfired pressure vessels (Bocquet, P., and Hukelmann, F., 2001, EPERC Bulletin, No. 5). The aim of this paper is to present an investigation performed by Luleå University of Technology within the ECOPRESS project (2000-2003) (http://www.ecopress.org), indicating possibilities towards economic design of pressure vessels made of the EN 1.4462, designation according to the European standard EN 10088-1 Stainless steels. The results show that FEA with von Mises yield criterion and isotropic hardening describe the material behaviour with a good agreement compared to tests and that 5% principal strain limit is too low and 12% is more appropriate.

Influence of Load Ratio, Rise Time and Waveform on the Corrosion Fatigue Crack Growth of Austenitic Stainless Steel in a PWR Primary Coolant Environment

2007 ◽  
Author(s):  
Norman Platts ◽  
David Tice ◽  
Keith Rigby ◽  
John Stairmand
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Weld Metal ◽  
Crack Growth ◽  
Growth Rates ◽  
Rise Time ◽  
Load Ratio ◽  
Loading Frequency ◽  
Primary Coolant ◽  
Crack Growth Rates

The rate of growth of flaws in reactor circuit components by fatigue is usually determined using the reference crack growth curves in Section XI of the ASME Boiler and Pressure Vessel Code. These curves describe the rate of crack propagation per cycle (da/dN) as a function of the applied stress intensity factor range (ΔK). No reference curves for water-wetted defects in austenitic stainless steels are currently available. This paper describes the results of testing of austenitic stainless steel and weld metal in simulated PWR primary coolant over a range of temperatures and mechanical loading conditions. Previous data presented by the authors on wrought stainless steel demonstrated that crack growth rates can be significantly enhanced by the PWR primary environment at temperatures between 150°C and 300°C. The current study extends these data to weld metal and also investigates the impact of other loading waveforms (e.g. trapezoidal loading) on the degree of environmental enhancement. The environmental enhancement increases significantly with reducing loading frequency and decreases with decreasing water temperature. The environmental influence on fatigue is shown to be independent of load ratio over the range R = 0.1 to R = 0.8. The level of enhancement is frequently smaller at very high R ratio (≥0.85) with the enhanced rates of fatigue frequently being unsustained at these high load ratios. There is a strong correlation between the rise time and the level of enhancement of crack growth rate over inert crack growth rates at all temperatures tested. Weld metal has been shown to exhibit similar behavior to wrought material over the whole temperature range studied although the apparent rates of enhancement relative to average inert crack growth rates are lower than found for wrought material. For complex loading waveforms (e.g. trapezoidal loading with hold periods at maximum or minimum load) it is possible predict the level of enhancement on the basis of the test data generated using simpler saw tooth loading regimes.

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