Journal of Materials Science

, Volume 18, Issue 12, pp 3671–3678 | Cite as

Tempered martensite embrittlement in Fe-Ni-C steel

  • H. Kwon
  • C. H. Kim
Papers

Abstract

The intergranular tempered martensite embrittlement in 6Ni-0.3C steel has been studied. For the evaluation of tempered martensite embrittlement, the impact toughness values were measured by Charpy V-notch tests. Variations in test temperature were applied to investigate its effect upon the intergranular tempered martensite embrittlement. The retained austenite was observed at the grain boundaries, as well as the lath boundaries in the as-quenched and 200° C tempered specimens. The specimen tempered at 300° C showed that the cementite platelets formed at the grain and the lath boundaries, following the decomposition of the retained austenite. The intergranular tempered martensite embrittlement associated with the formation of the grain boundary cementite was observed only when the impact test was performed below the critical test temperature (∼−40° C). It was found that the impact toughness is controlled by the intergranular fracture below the critical test temperature, while it is controlled by the transgranular fracture (i.e. the matrix toughness) above the critical test temperature. Therefore, the grain boundary cementite platelets can produce the intergranular tempered martensite embrittlement at low test temperatures (which are below the critical test temperature) where the impact toughness is controlled by the intergranular fracture, that is, by the incorporated action of the cementite platelets and the impurities at the grain boundaries.

Keywords

Polymer Austenite Martensite Cementite Test Temperature 

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Copyright information

© Chapman and Hall Ltd 1983

Authors and Affiliations

  • H. Kwon
    • 1
  • C. H. Kim
    • 1
  1. 1.Department of Materials Science and EngineeringKorea Advanced Institute of Science and TechnologySeoulKorea

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