Session: MF-02-06 Materials for Hydrogen Service-Test Methods 1

Paper Number: 122190

122190 - Performance of Regulator Valve Steels in Hydrogen and Hydrogen/natural Gas Blends 

Materials compatibility of ASTM A350 Grade LF2 steel with 75ksi UTS for high pressure hydrogen and mixed hydrogen/natural gas blend applications has been evaluated. A350-LF2 is a low alloy steel grade commonly used to manufacture forged piping components such as flange and forged fittings Utilizing a unique slow rate high pressure hydrogen testing system, extremely slow strain rate notched tension test (10^-7 1/s) and ultra-low frequency (2.78x10^-4 Hz) notched tension fatigue test were performed. Such slow loading rates, 2 to 3 orders of magnitudes slower than typical mechanical property testing in hydrogen in open literature, makes it possible to evaluate the steel under conditions more closely resembling the slow pressure variations caused by cyclic loading of pipeline under high pressure hydrogen or mixed hydrogen/natural gas service conditions. The mechanical property tests revealed a ~10% reduction in notched tensile strength under 1000-psi pure hydrogen (99.9999% research grade). Under 50% H₂ and 50% methane gas blend at 1000psi total pressure, only 4.5% reduction of notched tensile strength was measured. Furthermore, the ultra-low frequency fatigue test did not cause any visible hydrogen damage after 3000 cycles over a 5-month period of testing. The fractography analysis revealed quasi-cleavage fracture around the periphery of the fractured surface, which is indictive of hydrogen embrittlement (HE). However, the extent of quasi-cleavage fracture surface was limited to 0.1-0.2 mm deep. Specimens subjected to 50/50 mixed gas exhibited only isolated hydrogen embrittlement damage. The results from this study suggest that, in accordance with Ref 1, the tested A350-LF2 steel, a carbon and low alloy steel of tensile strength less than 70ksi and impurity control, was negligible or small HE effect under the testing conditions in this study. 

 

Reference:

1. Lee, J.A. 2016. Hydrogen Embrittlement. NASA Marshall Space Flight Center. NASA/TM-2016-218602. Huntsville, AL

Presenting Author: Zhili Feng Oak Ridge National Laboratory

Presenting Author Biography: Dr. Zhili Feng is a Distinguished R&D Staff and Group Leader of Materials Joining at Oak Ridge National Laboratory. He has been investigating the fundamental of hydrogen effects in metal, especially in welds of steels and alloys, and developing solutions to address them for the past 30 years.

Authors:

Zhili Feng Oak Ridge National Laboratory
Yong Chae Lim Oak Ridge National Laboratory
Yanli Wang Oak Ridge National Laboratory
Yiyu Wang Oak Ridge National Laboratory
Steven Kung Electric Power Research Institute