Hydrogen Embrittlement Mitigation by Engineering Grain Boundary Composition (HEnGB)

When exposed to water vapour, aqueous solutions or hydrogen gas, metallic components absorb hydrogen. The mobility of hydrogen and its interaction with the inner structural features of metals cause a significant decrease in their resistance to fracture and fatigue. This phenomenon, known as hydrogen embrittlement, has been responsible for numerous sudden catastrophic failures in metallic infrastructure. Moreover, this embrittlement effect poses major challenges to developing a safe and economical large-scale hydrogen infrastructure, which is critical to achieving net zero carbon emissions. This New Investigator Award, HEnGB, aims to deliver a new path for manufacturing alloys resistant to hydrogen.
The structure of metals is formed by grains, the intersections of which are higher energy interfaces, called grain boundaries (GBs). The accumulation or segregation of hydrogen atoms at GBs can cause cracking of these interfaces in the most relevant engineering metal systems, e.g., iron and steel, nickel, and aluminium. This is seen macroscopically as a sudden brittle fracture of components. Increasing the resistance of GBs to hydrogen would thus enable a breakthrough in alloy engineering for hydrogen applications. Previous studies have shown that changes in the character of GBs result in improvements in resistance to hydrogen embrittlement. However, this strategy has scaling problems, due to the complexity, cost and energy consumption of the thermomechanical processes needed to change GB character. Recent atomistic simulations have revealed that the strength of GBs to hydrogen can be modified depending on the amount and types of other elements that also accumulate at them. Exploiting these interactions of elements at the GBs, known as co-segregation, has the advantage of being controlled simply by heating at moderate temperatures, a process that requires less energy/CO2 and is cheaper than the one required to change GB character. HEnGB aims to prove that co-segregation...