In Situ Techniques for the Investigation of the Kinetics of Austenitization of Supermartensitic Stainless Steel

Frank Nießen, Matteo Villa, Daniel Apel, Olaf Keßler, Michael Reich, John Hald, Marcel A. J. Somers

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The austenitization and inter-critical annealing of X4CrNiMo16-5-1 (1.4418)
supermartensitic stainless steel were investigated in-situ with synchrotron X-ray diffraction (XRD), dilatometry and differential scanning calorimetry (DSC) under isochronal heating conditions. Austenitization occurred in two stages: the austenitization started at approx. 600 °C, decelerated at approx. 700 °C at 60 to 75 v.% of transformed austenite, and first resumed after heating for approx.
100 °C. This plateau in the transformation curve was more dominant for faster heating rates. Intercritical annealing at 675 and 700 °C revealed, that austenite can to a certain extent be stabilized to room-temperature. There was good agreement for the transformation curves yielded by dilatometry and XRD. Some deviation occurred due to the different applied heating principles, different temperature monitoring and the impact of surface martensite formation on the XRD measurement. The applicable temperature range for DSC as well as the close proximity of the Ac1- and the Curietemperature limited the usage of the technique in the present case.
Original languageEnglish
JournalMaterials Science Forum
Pages (from-to)1381-1386
Publication statusPublished - 2016


  • Supermartensitic stainless steel
  • Kinetic analysis
  • Austenitization
  • In-situ XRD
  • Dilatometry

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