Kinetics of internal oxidation of Mn-steel alloys

V. A. Lashgari, G. Zimbitas, C. Kwakernaak, W. G. Sloof

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Internal oxidation of three Mn-steel alloys with 1.7, 3.5 and 7.0 wt% Mn concentration at 950 °C in a gas mixture composed of nitrogen, hydrogen and water vapor with a dew point of +10°C was evaluated. For these alloys, the kinetics of internal oxidation are diffusion-controlled and obey parabolic growth rate law. The diffusion coefficient of oxygen and manganese determined from the observed internal oxidation kinetics are 3.35 × 10−7 and 4.14 × 10−12cm2/s at 950 °C, respectively. The formed internal oxide precipitates are mainly composed of MnO. The solubility product of MnO in an austenitic iron matrix is estimated to be (7.66 ± 0.18) × 10−9 mol fraction2 at 950 °C. The numerical simulation of concentration depth profiles of precipitated oxygen is in agreement with depth profiles determined with image analysis and X-ray microanalysis. Validity of the numerical simulation in case of the phase transformation was also tested. When a 1.7 wt% Mn-steel alloy is oxidized at 850 °C (instead of 950 °C) with a dew point of +12 °C partial phase transformation from austenite to ferrite takes place due to the Mn depletion. The associated precipitated oxygen concentration depth profile can be predicted accurately with numerical simulation.

Original languageEnglish
Pages (from-to)249-269
Number of pages21
JournalOxidation of Metals
Volume82
Issue number3-4
Early online date9 Jul 2014
DOIs
Publication statusPublished - 31 Oct 2014

Keywords

  • diffusion coefficient of manganese
  • diffusion coefficient of oxygen
  • internal oxidation
  • kinetics
  • MnO solubility product
  • modelling

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