Session: MF-02-02 Materials for Hydrogen Service-Effect of Gas Impurities

Paper Number: 123469

123469 - Non-Conservative Fracture Toughness Measurements Due to Trace Oxygen Impurities in Hydrogen Gas 

It is recognized that oxygen gas impurities can inhibit the deleterious effects of hydrogen gas on mechanical properties of steels. Most commonly, the effect of oxygen on hydrogen assisted fatigue has been studied. An increase in the measured hydrogen-assisted fracture toughness has been reported to result from oxygen gas impurities, but few efforts have been made to understand how much oxygen can be present in hydrogen gas without altering measured fracture toughness values. Hy-Performance Materials Testing measures the post-test oxygen content from every test performed in hydrogen gas and, as a result, has observed various instances where the measured oxygen content was unintentionally higher than intended. This paper will present some of these chance observations in which unintentionally elevated oxygen levels resulted in elevated fracture toughness measurements. Even a few tenths of a part per million have been observed to effectively inhibit hydrogen assisted fracture under certain conditions. These observations indicate the extreme importance of understanding and controlling the levels of trace oxygen impurities in hydrogen gas during fracture toughness measurements to avoid anomalously high toughness measurements. Finally, it should be noted that these observations apply only to fracture toughness measurements performed at laboratory test time scales (typically measured in hours); it is not currently understood whether similar trace levels of oxygen will inhibit crack growth in structures operated over operational time scales measured in months to years.

Presenting Author: Kevin Nibur Hy-Performance Materials Testing, LLC.

Presenting Author Biography: Kevin Nibur received his BS in Materials Engineering from Cal Poly, San Luis Obispo and a PhD in materials science from Washington State before spending 5 years working at Sandia National Laboratories in the Hydrogen Effects on Materials Laboratory. Dr. Nibur went on to found Hy-Performance Materials Testing in Bend, OR in 2011. HPMT is designed and operated specifically to meet the growing need for mechanical testing in hydrogen gas. Innovative approaches to all aspects of testing, including test chamber design, custom transducers, and lab safety maintain Hy-Performance Materials Testing as a premier mechanical testing laboratory.

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