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oa Oxidation Kinetics of Iron-Chromium and Iron-Chromium-Aluminium Alloys
Influence of secondary processes
- Source: Johnson Matthey Technology Review, Volume 69, Issue 1, Jan 2025, p. 38 - 44
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- 19 Dec 2023
- 28 Feb 2024
Abstract
The paper presents a mathematical model to describe thermogravimetric curves of the growth of scale with its simultaneous sublimation during oxidation of the surface of a metal or alloy. For alloys iron-chromium and iron-chromium-aluminium, a decrease in the effective reaction area as a result of the formation of the oxide of the alloying element lanthanum or yttrium (together with the formation of the main oxide: chromia or alumina) is considered. For metals, the case of increasing this area is also considered. During the oxidation of the chromia-forming alloy, another secondary process is added: the evaporation of chromia. Therefore, the equations describing the kinetics of changes in mass of these alloys are different. Equations are also considered that make it possible to describe the kinetics of the oxidation process taking into account the initial non-isothermal heating. The formal equations of the oxidation process with an increase in the reaction surface as a result of crushing metal powder are also considered. The resulting equations are used to describe the kinetic curves of changes in the mass of the samples under study. The given equations can be considered as a more accurate approximation to describe the experimental data than the formulas known so far.