Kinetics modeling of delta-ferrite formation and retainment during casting of supermartensitic stainless steel

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Abstract

The kinetics model for multi-component diffusion DICTRA was applied to analyze the formation and retainment of δ-ferrite during solidification and cooling of GX4-CrNiMo-16-5-1 cast supermartensitic stainless steel. The obtained results were compared with results from the Schaeffler diagram, equilibrium calculations and the Scheil model in Thermo-Calc, and validated by using microscopy and energy dispersive X-ray spectroscopy for chemical analysis on a cast ingot. The kinetics model showed that micro-segregation from solidification homogenizes within 2–3 s (70 °C) of cooling, and that retained δ-ferrite originates from the incomplete transformation to austenite. The kinetics model predicted the measured amount of δ-ferrite and the partitioning of Cr and Ni reasonably well. Further, it showed that slower cooling for the investigated alloy leads to less retained δ-ferrite, which is in excellent agreement with experimental results.
Original languageEnglish
JournalMaterials & Design
Volume118
Pages (from-to)138-145
ISSN0264-1275
DOIs
Publication statusPublished - 2017

Keywords

  • Casting
  • Delta ferrite
  • Diffusion
  • Kinetics modeling
  • Solid state transformation
  • Solidification
  • Supermartensitic stainless steel

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