Optimizing the hydrogen embrittlement resistance by Cu addition in a low carbon high strength steel

This study used the electrochemical hydrogen permeation test and the slow strain rate tensile (SSRT) test to examine the impact of Cu addition on hydrogen embrittlement (HE) in a low carbon high strength steel. The following method explains how Cu alloying affected HE resistance. (i) Cu alloying refined the prior austenite grain size, which increased the effective area of grain/packet/ block/lath boundaries and mitigated the strain localization, and thus provided additional reversible hydrogen traps, homogenized the hydrogen distribution and suppressed local accumulation of hydrogen at boundaries. (ii) Cu alloying promoted the Cu-rich precipitates, which had strong binding energy with hydrogen. Also, the "incoherent" fcc Cu-rich precipitates contrary to the "slightly coherent" Cu-rich with an energy-poor trap strongly trapped hydrogen and enhanced the HE resistance.