Determination of Concentration Dependent Diffusion Coefficients of Carbon in Expanded Austenite

Thomas S. Hummelshøj; Thomas L. Christiansen; Marcel A.J. Somers

doi:10.4028/www.scientific.net/DDF.273-276.306

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Determination of Concentration Dependent Diffusion Coefficients of Carbon in Expanded Austenite

Abstract:

In the present paper various experimental procedures to experimentally determine the concentration dependent diffusion coefficient of carbon in expanded austenite are evaluated. To this end thermogravimetric carburization was simulated for various experimental conditions and the evaluated composition dependent diffusivity of carbon derived from the simulated experiments was compared with the input data. The most promising procedure for an accurate determination is shown to be stepwise gaseous carburizing of thin foils in a gaseous atmosphere; the finer the stepsize, the more accurate the approximation of the diffusivity. Thermogravimetry was applied to continuously monitor the weight change of thin foils of AISI 316 during carburizing in CO-H2 gas mixtures for one of the simulated experimental procedures.