Effects of Ti alloying on resistance to hydrogen embrittlement in (Nb+Mo)-alloyed ultra-high-strength hot-stamping steels

Jisung Yoo, Min Chul Jo, Min Cheol Jo, Seongwoo Kim, Jinkeun Oh, Jian Bian, Seok Su Sohn, Sunghak Lee

Research output: Contribution to journalArticle

Abstract

A boron-containing 1.8–2.0-GPa-grade hot-stamping steel, which has been attracting great attentions as reinforcing automotive parts, often leads to the deteriorated resistance to hydrogen embrittlement due to its high strength level. The micro-alloying elements such as Nb and Mo have been known to improve the resistance to hydrogen embrittlement by refining grains and providing interfaces of precipitates. Ti is also utilized for the mentioned purposes; however, the effect of Ti on hydrogen embrittlement, particularly in (Nb + Mo) multi-alloyed system, has not been revealed clearly yet. In this study, therefore, the alloying effects of Ti on resistance to hydrogen embrittlement were investigated via controlling Ti content and conducting slow-strain-rate tensile (SSRT) tests and thermal desorption analyses (TDA) after the hydrogen charging. The complex addition of Nb, Mo, and Ti promotes the formation of nanoscale (Nb,Ti)C and (Nb,Mo,Ti)C complex precipitates along with coarse Ti(C,N) particles. The increased Ti content to 0.03 wt% increases the volume fraction of nanoscale precipitates, which effectively refines the prior austenite grain size and interfacial incoherency, thereby providing stable hydrogen trapping sites with the higher activation energy for hydrogen desorption. Although the increased Ti also promotes the formation of brittle coarse Ti(C,N) particles, this negative effect of the particles can be minimized or prevented by the decrease in particle size due to the interaction with Nb and Mo.

Original languageEnglish
Article number139763
JournalMaterials Science and Engineering A
Volume791
DOIs
Publication statusPublished - 2020 Jul 22

Keywords

  • 32MnB5 steel
  • Complex carbide
  • Grain refinement
  • Hot-stamping steel
  • Resistance to hydrogen embrittlement

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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