Comparison of Microstructure and Hardness between High-carbon and High-nitrogen Martensites

  • Tsuchiyama Toshihiro
    Department of Materials Science and Engineering, Kyushu University International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University
  • Inoue Kurato
    Graduate Student, Kyushu University
  • Hyodo Katsutoshi
    Graduate Student, Kyushu University
  • Akama Daichi
    Department of Materials Science and Engineering, Kyushu University
  • Nakada Nobuo
    Department of Materials Science and Engineering, Tokyo Institute of Technology
  • Takaki Setsuo
    Research Center for Steel, Kyushu University
  • Koyano Tamotsu
    Cryogenics Division, Research Facility Center, University of Tsukuba

Abstract

<p>The microstructure and hardness of martensite in Fe–C and Fe–N alloys with up to 7.5 at% contents of carbon and nitrogen, respectively, were compared. Their difference in hardness was discussed based on four strengthening mechanisms. The martensitic structures of Fe–C and Fe–N alloys with equal contents of carbon and nitrogen, respectively, were nearly identical, except for the amount of retained austenite. Furthermore, Fe–C alloy was considerably harder than Fe–N alloy. This discrepancy gradually increased with carbon and nitrogen contents. The enhanced hardness of Fe–C alloy martensite was attributed to its higher dislocation density and the stronger pinning force of interstitial carbon atoms on dislocations.</p>

Journal

  • ISIJ International

    ISIJ International 59 (1), 161-168, 2019-01-15

    The Iron and Steel Institute of Japan

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