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Hydrogen embrittlement testing of austenitic stainless steels SUS 316 and 316L

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Title: Hydrogen embrittlement testing of austenitic stainless steels SUS 316 and 316L
Author: Bromley, Darren Michael
Degree Master of Applied Science - MASc
Program Materials Engineering
Copyright Date: 2008
Publicly Available in cIRcle 2008-06-18
Subject Keywords Hydrogen embrittlement; Stainless steel; 316L; Martensite; Stacking fault energy
Abstract: The imminent emergence of the hydrogen fuel industry has resulted in an urgent mandate for very specific material testing. Although storage of pressurized hydrogen gas is both practical and attainable, demands for increasing storage pressures (currently around 70 MPa) continue to present unexpected material compatibility issues. It is imperative that materials commonly used in gaseous hydrogen service are properly tested for hydrogen embrittlement resistance. To assess material behavior in a pressurized hydrogen environment, procedures were designed to test materials for susceptibility to hydrogen embrittlement. Of particular interest to the field of high-pressure hydrogen in the automotive industry, austenitic stainless steels SUS 316 and 316L were used to validate the test programs. Tests were first performed in 25 MPa helium and hydrogen at room temperature and at -40°C. Tests in a 25 MPa hydrogen atmosphere caused embrittlement in SUS 316, but not in 316L. This indicated that alloys with higher stacking fault energies (316L) are more resistant to hydrogen embrittlement. Decreasing the test temperature caused slight embrittlement in 316L and significantly enhanced it in 316. Alternatively, a second set of specimens was immersed in 70 MPa hydrogen at 100°C until reaching a uniform concentration of absorbed hydrogen. Specimens were then loaded in tension to failure to determine if a bulk saturation of hydrogen provided a similar embrittling effect. Neither material succumbed to the effects of gaseous pre-charging, indicating that the embrittling mechanism requires a constant supply of hydrogen at the material surface rather than having bulk concentration of dissolved hydrogen. Permeation tests were also performed to ensure that hydrogen penetrated the samples and to develop material specific permeation constants. To pave the way for future work, prototype equipment was constructed allowing tensile or fatigue tests to be performed at much higher hydrogen pressures. To determine the effect of pressure on hydrogen embrittlement, additional tests can be performed in hydrogen pressures up to 85 MPa hydrogen. The equipment will also allow for cyclic loading of notched tensile or compact tension specimens for fatigue studies.
URI: http://hdl.handle.net/2429/925

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