Effect of Cut-edge Properties on Hydrogen Embrittlement of Three High-Mn Steels

This study aims to fill a knowledge gap about the cutting effect on hydrogen embrittlement behavior of three different high manganese steels (HMnS). Slow strain rate tests are carried out on uncharged and hydrogen-charged specimens which were processed by four cutting technologies: electrical discharge machining, laser cutting, abrasive waterjet cutting, and blanking. Detailed investigations of the cut-edge quality in terms of microstructure and mechanical properties elucidated the cutting influences on hydrogen-influenced fracture in HMnS.
Electrical discharge machining and laser cutting belong to thermal cutting which have limited influences on the initial microstructure and produce a relatively smooth cut-edge. Both abrasive waterjet cutting and blanking involve plastic deformation, but blanking generates a significant hardening effect with microvoids and distorted grains in the shear-affected zone (SAZ). Due to these factors, the blanked specimens show the worst tensile ductility regardless of hydrogen charging. Conversely, without edge hardening, the thermal-cut specimens exhibit less sensitivity to hydrogen embrittlement. The SAZ of the blanked specimens behaves as a precrack effect during tension, which is facilitated by the deformation twin.