Temperature Dependence of Fatigue Crack Growth in Low-Alloy Steel Under Gaseous Hydrogen

2018 ◽  
Author(s):  
Osamu Takakuwa ◽  
Saburo Matsuoka ◽  
Saburo Okazaki ◽  
Michio Yoshikawa ◽  
Junichiro Yamabe ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Binding Energy ◽  
Fatigue Crack Growth ◽  
Temperature Dependence ◽  
Crack Growth ◽  
Site Occupancy ◽  
Hydrogen Gas ◽  
Temperature Elevation ◽  
Trap Site ◽  
Thermal Equilibrium State

In order to elucidate the temperature dependence of hydrogen-enhanced fatigue crack growth (FCG), the FCG test was performed on low-alloy Cr-Mo steel JIS-SCM435 according to ASTM E647 using compact tension (CT) specimen under 0.1–95 MPa hydrogen-gas at temperature ranging from room temperature (298 K) to 423 K. The obtained results were interpreted according to trap site occupancy under thermal equilibrium state. The FCG was significantly accelerated at RT under hydrogen-gas, that its maximum acceleration rate of the FCG was 15 at the pressure of 95 MPa at the temperature of 298 K. The hydrogen-enhanced FCG was mitigated due to temperature elevation for all pressure conditions. The trap site with binding energy of 44 kJ/mol dominated the temperature dependence of hydrogen-enhanced FCG, corresponding approximately to binding energy of dislocation core. The trap site (dislocation) occupancy is decreased with the temperature elevation, resulting in the mitigation of the FCG acceleration. On the basis of the obtained results, when the occupancy becomes higher at lower temperature, e.g. 298 K, hydrogen-enhanced FCG becomes more pronounced. The lower occupancy at higher temperature does the opposite.

Effects of Gaseous Hydrogen on Fatigue Crack Growth Behavior of Low Carbon Steel

2009 ◽  
Author(s):  
Dongsun Lee ◽  
Hide-aki Nishikawa ◽  
Yasuji Oda ◽  
Hiroshi Noguchi
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Ductile Fracture ◽  
Crack Growth ◽  
Strain Range ◽  
Hydrogen Gas ◽  
Crack Growth Behavior ◽  
Low Carbon ◽  
Nitrogen Gas

In order to investigate the effects of hydrogen on the fatigue crack growth behavior of low carbon steel JIS S10C, bending fatigue tests were carried out using a specimen with a small blind artificial hole in a low pressure pure hydrogen gas atmosphere. The results show that the fatigue crack growth rate in hydrogen gas is higher than that in nitrogen gas, moreover, the degree of acceleration is greater in the high strain range. In fractography, intergranular facets mixed with ductile fracture and quasi-cleavage fracture with brittle striations appear in a hydrogen gas environment, while only ductile fracture mainly appears in nitrogen gas. In the low growth rate range, many intergranular facets are seen on the ductile fracture surface, and in the higher growth rate range, quasi-cleavage facets increase as the growth rate increases. The growth rate of a small crack in nitrogen gas can be expressed by dl/dN ∝ Δεpnl in the wide range of applied total strain range Δεt. The same type equation is also satisfied in hydrogen gas, but in the narrow range roughly from Δεt = 0.25% to Δεt = 0.37%. The fracture surface in this range shows only intergranular facets and a ductile morphology, but no quasi-cleavage fracture. Although the crack growth mechanism in hydrogen is different from that in nitrogen, observation of the mechanism of intergranular facet formation shows a similarity to the mechanism in nitrogen in which the slip-off mechanism of crack growth is valid. The formation of intergranular facets is also closely related to the slip behavior influenced by hydrogen. This means that there exists a high possibility for the application of the small crack growth law inhydrogen to not only S10C, but also to other carbon steels in which the intergranular facet appears.

The Effect of Microstructure on the Hydrogen-Assisted Fatigue of Pipeline Steels

2013 ◽  
Author(s):  
Andrew J. Slifka ◽  
Elizabeth S. Drexler ◽  
Douglas G. Stalheim ◽  
Robert L. Amaro ◽  
Damian S. Lauria ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
High Pressures ◽  
Load Ratio ◽  
Fatigue Tests ◽  
Hydrogen Gas ◽  
The Other ◽  
Stress Intensity Factor Range ◽  
Pipeline Steels

Tests on the fatigue crack growth rate were conducted on four pipeline steels, two of grade API 5L-X52 and two API 5L-X70. One X52 material was manufactured in the mid-1960s and the other was manufactured in 2011. The two X70 materials had a similar vintage and chemistry, but the microstructure differs. The fatigue tests were performed in 5.5 and 34 MPa pressurized hydrogen gas, at 1 Hz and (load ratio) R = 0.5. At high pressures of hydrogen and high values of the stress intensity factor range (ΔK) there is no difference in the fatigue crack growth rates (da/dN), regardless of strength or microstructure. At low values of ΔK, however, significant differences in the da/dN are observed. The older X52 material has a ferrite-pearlite microstructure; whereas, the modern X52 has a mixture of polygonal and acicular ferrites. The X70 materials are both predominantly polygonal ferrite, but one has small amounts (∼5%) of upper bainite, and the other has small amounts of pearlite (<2%) and acicular ferrite (∼5%). We discuss the fatigue test results with respect to the different microstructures, with particular emphasis on the low ΔK regime.

scholarly journals Hydrogen Effects on Fatigue Crack Growth Rates in Pipeline Steel Welds

2016 ◽  
Author(s):  
Joe A. Ronevich ◽  
Brian P. Somerday
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Rates ◽  
Pipeline Steel ◽  
Hydrogen Gas ◽  
Friction Stir Weld ◽  
Friction Stir ◽  
Welding Processes ◽  
Crack Growth Rates

Fatigue crack growth rate (da/dN) versus stress intensity factor range (ΔK) relationships were measured for various grades of pipeline steel along with their respective welds in high pressure hydrogen. Tests were conducted in both 21 MPa hydrogen gas and a reference environment (e.g. air) at room temperature. Girth welds fabricated by arc welding and friction stir welding processes were examined in X65 and X52 pipeline grades, respectively. Results showed accelerated fatigue crack growth rates for all tests in hydrogen as compared to tests in air. Modestly higher hydrogen-assisted crack growth rates were observed in the welds as compared to their respective base metals. The arc weld and friction stir weld exhibited similar fatigue crack growth behavior suggesting similar sensitivity to hydrogen. A detailed study of microstructure and fractography was performed to identify relationships between microstructure constituents and hydrogen accelerated fatigue crack growth.

Mechanical Properties of a New Nitrogen-Strengthened Stainless Steel With Reduced Amount of Ni and Mo in High Pressure Gaseous Hydrogen

2013 ◽  
Author(s):  
Kazuhisa Matsumoto ◽  
Shinichi Ohmiya ◽  
Hideki Fujii ◽  
Masaharu Hatano
Keyword(s):  
High Pressure ◽  
Stainless Steel ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
High Strength ◽  
Hydrogen Gas ◽  
Fracture Surfaces ◽  
Growth Properties ◽  
Pressure Hydrogen

To confirm a compatibility of a newly developed high strength stainless steel “NSSC STH®2” for hydrogen related applications, tensile and fatigue crack growth properties were evaluated in high pressure hydrogen gas up to 90MPa. At temperatures between −40 and 85°C, no conspicuous deterioration of tensile properties including ductility was observed even in 90 MPa hydrogen gas at −40°C while strength of STH®2 was higher than SUS316L. Although a slight drop of reduction of area was recognized in one specimen tested in 90 MPa hydrogen gas at −40°C, caused by the segregation of Mn, Ni and Cu in the laboratory manufactured 15mm-thick plate, it was considerably improved in the large mill products having less segregation. Fatigue crack growth rates of STH®2 in high pressure hydrogen gas were almost the same as that of SUS316L in air. Although fatigue crack growth rate in air was considerably decelerated and lower than that in hydrogen gas at lower ΔK region, this was probably caused by crack closure brought by oxide debris formed on the fracture surfaces near the crack tip by the strong contact of the fracture surfaces after the fatigue crack was propagated. By taking the obtained results into account, it is concluded that NSSC STH®2 has excellent properties in high pressure hydrogen gas in addition to high strength compared with standard JIS SUS316L.

On Material Qualification and Strength Design for Hydrogen Service

2015 ◽  
Author(s):  
Junichiro Yamabe ◽  
Hisao Matsunaga ◽  
Yoshiyuki Furuya ◽  
Saburo Matsuoka
Keyword(s):  
High Pressure ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Safety Factor ◽  
Fatigue Testing ◽  
Hydrogen Gas ◽  
Multiplier Method ◽  
Notched Specimens ◽  
Pressure Hydrogen

To clarify the usefulness of the safety factor multiplier method for hydrogen components given in the CHMC1-2014 standard, we performed slow-strain-rate tensile and fatigue testing by using smooth and notched specimens in air and in high-pressure hydrogen gas. We also conducted fatigue-crack growth tests by using compact tension specimens in air and in hydrogen gas. Testing of notched specimens sampled from a Cr–Mo steel gave a safety factor multiplier of 3.0. This value agreed well with that predicted by crack growth analysis taking into account hydrogen-enhanced fatigue-crack growth. The safety factor multipliers of types 304, 316, and 316L austenitic stainless steels were predicted to be 2.0, 1.6, and 1.3, respectively, from their fatigue-crack growth behaviors. The safety factor based on the safety factor multiplier method seems to be overly conservative for the various steels in high-pressure hydrogen gas service. We therefore propose a new and promising design method for specific component applications that is based on design by rule and design by analysis. The importance of operational histories of components for hydrogen service is introduced to permit the precise prediction of their fatigue lives.

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