Hydrogen embrittlement of steels: Mechanical properties in gaseous hydrogen

As the exigency for decarbonizing sectors such as utilities, heavy-duty transportation, and manufacturing has risen, interest in hydrogen technologies has intensified accordingly. Among the safety issues being addressed for hydrogen technologies is the potential for hydrogen embrittlement of steels, which are commonly specified for pressure boundaries in containment components. From an engineering perspective, hydrogen embrittlement of steels can be managed through conventional design and fitness-for-service (FFS) practices provided the mechanical property inputs are measured appropriately, i.e., testing of steels is performed in the hydrogen environment. Given the increasing need for managing hydrogen embrittlement to safely operate high-pressure containment components, the purpose of this review is to comprehensively survey and critically assess the literature on the following mechanical properties of steels in gaseous hydrogen that serve as inputs to design and FFS analyses: threshold stress-intensity factor or threshold J-integral for subcritical, time-dependent cracking, fatigue crack growth rate, and total fatigue life. The review focuses on such mechanical properties in gaseous hydrogen for carbon-manganese (C-Mn) steels, low-alloy steels, austenitic stainless steels, duplex stainless steels, as well as the ferritic and martensitic stainless steels, since these are most pertinent to containment components in hydrogen technology. Three high-level conclusions from the review are the following: 1) mechanical property data for C-Mn and low-alloy steels in hydrogen gas are sufficiently mature so that conservative limits can be specified for design and FFS analyses, 2) mechanical property data for austenitic stainless steels must be supplemented with additional measurements, particularly from specimens tested in high-pressure hydrogen gas, before conservative limits can be defined for design and FFS analyses, and 3) mechanical property data for ferritic, martensitic, and duplex stainless steels in hydrogen gas are so scarce that design and FFS analyses covering wide ranges of steel grades and component service conditions are currently not feasible.