Recent research progress in hydrogen embrittlement of additively manufactured metals – A review

Hydrogen is considered as a primary energy carrier for the hydrogen economy. However, hydrogen embrittlement (HE) is an inescapable problem that needs to be solved because metals, particularly steels, are commonly used in the transportation and storage of hydrogen, and because HE occurs in high-performance structural components in contact with moisture or hydrogen. In particular, HE concerns of additively produced alloys should be addressed, because additive manufacturing (AM) can provide significant advantages in the manufacturing of such structural components. This review overviews the recent research progress in HE of metals fabricated using AM. This review introduces AM and HE and summarises and discusses (i) the factors that influence the HE of AM metals, (ii) possible mechanisms of HE, (iii) the differences and similarities of HE behaviour between metals processed by AM and those produced through conventional manufacturing processes, and (iv) the current challenges and research gaps of HE in AM metals. The review covers structural steels, titanium alloys, tool steels, nickel-based superalloys, stainless steels and high-entropy alloys.