Hydrogen trapping at nanoscale alloy carbides in high-strength steels

Hydrogen, when dissolved in metal or alloy lattice, can render the otherwise ductile material brittle. This phenomenon, namely hydrogen embrittlement (HE), has been a persistent obstacle for the application and development of high strength steels. One effective means to enhance the high strength steels resistance to HE is to introduce nanoscale alloy carbides (NACs) into the microstructure, evidenced by the increased emission temperature of hydrogen and delayed fracture under the same hydrogen charging condition. The role of NACs in HE is often attributed to them trapping hydrogen. Nonetheless, with NACs being nanoscale in size, their trapping effects on hydrogen are difficult to quantify in experiments. In this project, we employ first-principle calculations which provide an accurate way to examine NACs and their interplay with hydrogen with atomic resolution. Several candidate NACs in high-strength steels will be considered. For each of them, the hydrogen adsorption energetics and diffusion kinetics at the NAC will be investigated. The individual roles of the NAC induced coherent lattice strain and NAC/metal interface structure will be clarified. In addition, preliminary studies will be conducted on incoherent NAC/metal interfaces. The results obtained will provide quantitative assessments of the role of NACs on hydrogen trapping, offering important bottom-up insights for the microstructure engineering of high-strength steels against HE.

Faculty Supervisor:

Jun Song

Student:

YUSHUAI XU

Partner:

Discipline:

Engineering - chemical / biological

Sector:

University:

McGill University

Program:

Globalink