Effects of tempered microstructure and hydrogen concentration on hydrogen-induced embrittlement susceptibility of 10B21 screws at low temperature

Secondary ion mass spectroscopy (SIMS) was used to examine the hydrogen atoms in low-carbon boron (10B21) steel screws. The effects of baking and tempering treatments on the hydrogen-induced embrittlement (HIE) susceptibility of the screws were investigated. SIMS results confirmed that hydrogen concentration decreased with increasing baking duration, and thus increased the engineering reliability of the screws. For low-temperature applications, 10B21 screws must be baked for a longer duration to prevent HIE. The observed tempered martensite was composed of ferrite and cementite, which could limit the movement of hydrogen atoms. At higher tempering temperature, the structure of the screw matrix became finer, reducing the HIE susceptibility. 10B21 screws tempered at a high temperature thus had good ability to resist low-temperature HIE.