Characterisation of non-stoichiometric cementite (Fe3C). (March 2020)

• Record Type: Journal Article
• Authors: Schneider, Andre; Palm, Martin
• Is Part Of: Calphad. Volume 68(2020)
• Publication Date: 2020-03
• Subjects: Cementite -- Iron-carbon -- Experimental; Phase diagrams -- Data processing -- Periodicals; Thermochemistry -- Data processing -- Periodicals; Diagrammes de phases -- Informatique -- Périodiques; Thermochimie -- Informatique -- Périodiques; Thermodynamica; Electronic journals; 541.363
• DOI: 10.1016/j.calphad.2019.101689
• Languages: English
• ISSNs: 0364-5916

Abstract

Abstract: In order to measure the composition range of cementite, a sample has been prepared by carburisation at 700 °C at a high carbon activity aC = 100. Such strongly carburising conditions normally result in a quick onset of the high-temperature corrosion process metal dusting, which leads to cementite decomposition at the surface. The effect of sulphur to retard this corrosion process was used by adding a small amount of 1 ppm H2 S to the gas mixture. The measurements of the carbon contents of the cementite particles formed at the sample surface were performed by using electron-probe microanalysis (EPMA). It was found that cementite (Fe3 C) which was formed at a very high carbon activity aC » aC (Fe3 C/α-Fe) reveals a measurable carbon gradient. The homogeneity range of cementite at 700 °C in the investigated sample was determined to be of at least 0.6 at.% carbon. Note: this study has been performed at Max-Planck-Institut für Eisenforschung already two decades ago, but it was not yet published internationally. However, the respective experimental results were already described in [1].