Hydrogen Embrittlement of Maraging Steel Tension Bolt / Wasserstoffversprödung eines Spannbolzens aus Maraging-Stahl

TLDR: An ultra-high strength maraging steel bolt, used to fasten steel bands in an aerospace separation system failed prematurely under a sustained stress of about 42 % of its tensile strength during its qualification tests prior to acceptance for flight as mentioned in this paper.

Abstract: An ultrahigh strength maraging steel bolt, used to fasten maraging steel bands in an aerospace separation system failed prematurely under a sustained stress of about 42 % of its tensile strength during its qualification tests prior to acceptance for flight. The metallographic investigation of this failed bolt revealed that certain defects on its surface were filled up by multipass welding causing an inhomogeneous microstructure as well as the accumulation of hydrogen at its sharp thread roots. This caused the delayed failure of the bolt at a lower stress level