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Effect of χ Phase on Impact Toughness of 25Cr-7Ni-2Mo-4W Super Duplex Stainless Steel

25Cr-7Ni-2Mo-4W 슈퍼 2상 스테인리스강의 충격인성에 미치는 χ상의 영향

  • Received : 2012.11.16
  • Accepted : 2013.04.19
  • Published : 2013.04.30

Abstract

This study was carried out to investigate the precipitation behavior of the ${\chi}$ phase and the impact toughness of 25%Cr-7%Ni-2%Mo-4%W super duplex stainless steel. The ${\chi}$ phase was precipitated in the early stage of aging, and with the increasing aging time. However, after reaching a maximum value, the number decreased as a result of the gradual transformation of the ${\chi}$ phase into the ${\sigma}$-phase. It was proved that the ${\chi}$ phase was an intermetallic compound, which represented a lower nickel concentration, higher chromium and molybdenum concentrations, and very higher tungsten concentration compared to the matrix phases. It also showed higher molybdenum and tungsten concentrations than the ${\sigma}$ phase. The decomposition of the ferrite phase into the ${\gamma}_2$ and ${\sigma}$ phases was retarded by W substitution for Mo. Thus, the number of ${\chi}$ phases increased. The impact value was decreased by the substitution of W for Mo. The impact toughness rapidly decreased with time when the ${\chi}$ phase began to precipitate in the initial stage of aging. The impact toughness was, therefore, greatly influenced for the precipitation of the ${\chi}$ phase.

Keywords

${\chi}$ phase;Impact toughness;Super duplex stainless stee;W substitution;Aging treatment

References

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Cited by

  1. Effect of χ Phase on Impact Toughness of 25Cr-7Ni-2Mo-4W Super Duplex Stainless Steel vol.27, pp.2, 2013, https://doi.org/10.5574/KSOE.2013.27.2.075