Development of high-chromium ferritic heat-resistant steels with high-nitrogen addition

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Abstract

New ferritic heat resistant steels with high nitrogen content were developed and these microstructure and the mechanical properties at high temperature were evaluated. 0.3 mass% N could be added into ferritic steels without blow holes by applying pressurized melting methods with pressurized atmosphere up to 4.0 MPa. The high nitrogen ferritic heat resistant steels contained several kind of nitrides within the lath martensitic structure. V-rich coarse particles were identified as crystallized VN. Fine VN or Cr2N particles were precipitated on the martensitic grain boundaries depending on the amount of V content. The martensitic structure in the high nitrogen steels contained a hierarchical structure of martensitic lath, block, packet and prior austenitic grain. These martensitic structure satisfied the K-S relationship as with the conventional carbon steel. The creep strength of the developed steels were comparable to Gr.91 steel though weaker than Gr.92. It is required additional precipitates other than nitrides for further strengthening of the developed steels.

Original languageEnglish
Pages (from-to)64-72
Number of pages9
JournalTetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan
Volume103
Issue number1
DOIs
Publication statusPublished - Jan 1 2017

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All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Physical and Theoretical Chemistry
  • Metals and Alloys
  • Materials Chemistry

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