oa Oxidation Kinetics of FeCr and FeCrAl Alloys: Influence of Secondary Processes

The paper presents a mathematical model for describing of thermogravimetric curves of growth of scale with its simultaneous sublimation during oxidation of the surface of a metal or alloy. For alloys FeCr and FeCrAl, 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 - Cr2O3 or Al2O3) 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 Cr2O3. 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.