Abstract

High pressure high temperature (HPHT) design is a significant new challenge facing the subsea sector, particularly in the Gulf of Mexico. API 17TR8 provides HPHT Design Guidelines, specifically for subsea applications. Fatigue endurance (i.e., S–N) and fracture mechanics design are both permitted, depending on the criticality of the component. Both design approaches require material properties generated in corrosive environments, such as seawater with cathodic protection and/or sour production fluids. In particular, it is necessary to understand sensitivity to cyclic loading frequency (for both design approaches), crack growth rates (CGR) (for fracture mechanics approach) as well as fracture toughness performance. For many subsea components, the primary source of fatigue loading is associated with the start-up and subsequent shutdown operation of the well, with long hold periods in-between, during which static crack growth (CG) could occur. These are the two damage modes of most interest when performing a fracture mechanics based analysis. This paper presents the preliminary results of a novel single specimen test method that was developed to provide fatigue crack growth rate (FCGR) and fracture toughness data in corrosive environments, in a timeframe that is compatible with subsea HPHT development projects. Test data generated on alloy 625+ in seawater with cathodic protection are presented along with a description of how the test method was developed. A crack tip strain rate based formulation was applied to the data to rationalize the effect of frequency, stress intensity factor range (ΔK), and maximum stress intensity factor (Kmax).

References

References
1.
Esakul
,
K. A.
, and
Martin
,
J. W.
,
2004
, “
High Strength Fasteners for Subsea Applications
,”
CORROSION
,
New Orleans, LO
, Mar. 28–Apr. 1, Paper No. 04151.https://www.onepetro.org/conference-paper/NACE-04151
2.
Kernion
,
S. J.
,
Magee
,
J. H.
,
Werely
,
T. N.
, and
Maxwell
,
P.
,
2014
, “
Hydrogen Embrittlement Susceptibility of Precipitation Strengthened Ni-Base Superalloys
,”
Offshore Technology Conference (OTC)
,
Houston, TX
, May 5–8, Paper No. 25177.10.4043/25177-MS
3.
Kernion
,
S. J.
,
Magee
,
J. H.
,
Heck
,
K. A.
, and
Werely
,
T. N.
,
2015
, “
Effect of Microstructure and Processing on the Hydrogen Embrittlement of Ni-Base Superalloys
,”
CORROSION
,
Dallas, TX
, Mar. 15–19, Paper No. 6053.https://www.onepetro.org/conference-paper/NACE-2015-6053
4.
Rollins
,
B. C.
,
Carlton
,
C.
,
Piza Paes
,
M.
, and
Thodla
,
R.
,
2016
, “
Development of Test Methodology to Evaluate High Strength Nickel Based Alloys Under Cathodic Protection
,”
CORROSION
,
Vancouver, BC, Canada
, Mar. 6–10, Paper No. C2016-7828.https://www.onepetro.org/conference-paper/NACE-2016-7828
5.
Thodla
,
R.
,
Collins
,
B. R.
,
Holtam
,
C.
, and
Scott
,
H.
,
2017
, “
Effect of Strain Rate on the Fatigue and Static Crack Growth Rate of UNS N07718 Under Cathodic Polarization
,”
CORROSION
,
New Orleans, LA
, Mar. 26–30, Paper No. C2017-9669.https://www.onepetro.org/conference-paper/NACE-2017-9669
6.
ASTM,
2000
, “
Standard Test Method for Measurement of Creep Crack Growth Rates in Metals
,”
ASTM International
,
West Conshohocken, PA
, Standard No. E1457.
7.
ASTM
,
2012
, “
Standard Test Method for Linear-Elastic Plane-Strain Fracture Toughness KIC of Metallic Materials
,”
ASTM International
,
West Conshohocken, PA
, Standard No. E399.
8.
ASTM
,
2013
, “
Standard Test Method for Determining Threshold Stress Intensity Factor for Environment-Assisted Cracking of Metallic Materials
,”
ASTM International
,
West Conshohocken, PA
, Standard No. E1681-03.
9.
Koul
,
M. G.
, and
Knudsen
,
E. C.
,
2012
, “
Environmentally Assisted Cracking Evaluation of a Large UNS N07725 Forging Under Cathodic Protection Conditions
,”
Corrosion
,
68
(
5
), pp.
449
460
.10.5006/0010-9312-68.5.449
10.
Lillard
,
J.
,
1998
, “
Environment Assisted Cracking of a Nickel-Based Super Alloy in Hydrogen-Producing Environment
,”
University of Virginia
,
Charlottesville, VA
.
11.
Moody
,
N. R.
,
Stoltz
,
R. E.
, and
Perra
,
M. W.
,
1987
, “
The Effect of Hydrogen on Fracture Toughness of the Fe-Ni-Co Superalloy IN903
,”
Metall. Trans. A
,
18
(
8
), pp.
1469
1492
.10.1007/BF02646659
12.
Harris
,
Z. D.
,
Dolph
,
J. D.
,
Pioszak
,
G. L.
,
Rincon Troconis
,
B. C.
,
Scully
,
J. R.
, and
Burns
,
J. T.
,
2016
, “
The Effect of Microstructural Variation on the Hydrogen Assisted Cracking of Monel K-500
,”
Metall. Trans. A
,
47
(
7
), pp.
3488
3510
.10.1007/s11661-016-3486-7
13.
Ford
,
F. P.
,
1988
, “
Status of Research on Environmentally Assisted Cracking in LWR Pressure Vessel Steels
,”
ASME J. Pressure Vessel Technol.
,
110
(
2
), pp.
113
128
.10.1115/1.3265576
14.
Ford
,
F. P.
, and
Andresen
,
P. L.
,
1989
, “
Stress Corrosion Cracking of Low Alloy Steels in 288 °C Water
,”
CORROSION
,
New Orleans, LA
, Paper No. 498.
15.
Shoji
,
T.
,
Takahashi
,
H.
,
Suzuki
,
M.
, and
Kondo
,
T.
,
1981
, “
A New Parameter for Characterizing Corrosion Fatigue Crack Growth
,”
ASME J. Eng. Mater. Technol.
,
103
(
4
), pp.
298
304
.10.1115/1.3225020
16.
BSI,
2013
, “
Guide to Methods for Assessing the Acceptability of Flaws in Metallic Structures
,”
BSI
,
London
, Standard No. BS 7910.
17.
Sowards
,
J. W.
,
Weeks
,
T. S.
, and
McColskey
,
J. D.
,
2013
, “
The Influence of Simulated Fuel-Grade Ethanol on Fatigue Crack Propagation in Pipeline and Storage-Tank Steels
,”
Corros. Sci.
,
75
, pp.
415
425
.10.1016/j.corsci.2013.06.026
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