Hydrogen embrittlement is a potentially catastrophic failure mode of high strength steel fasteners. One of the leading indicators of susceptibility to this phenomenon is hardness. While the susceptibility of case hardened fasteners is undisputed, minimal data exist to explain how the variables of case hardness, case depth, and core hardness work together to influence overall fastener susceptibility to failure. Peak Innovations Engineering principal engineer John Medcalf investigated this topic, and along with co-authors Brian Thomas and Salim Brahimi, presents his findings in the following paper. The research indicates that hardness levels found in current fastener standards may be susceptible to hydrogen embrittlement in corrosive environments. Future research is planned to address susceptibility to internal hydrogen embrittlement.
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Medcalf, J.S., Thomas, B.G., and Brahimi, S.V., “Hydrogen Embrittlement Susceptibility of Case
Hardened Steel Fasteners,” SAE Technical Paper 2018-01-1240, 2018, doi:10.4271/2018-01-1240