Numerical study of the influence of the total mass of oxide formed during heating on the parabolic kinetic constant kp characterizing the high temperature oxidation rate of chromia-forming alloys

摘要

Thermogravimetry is a very useful technique for accessing the kinetic description of the high temperature oxidation progress. Classical methods for deducing the value of k_p, the kinetic constant characterizing the parabolic oxidation in isothermal condition may lead sometimes to underestimated values, often minimizing the real oxidation rate. Here, exploiting some real experimental data, a mathematical study of the kinetic of oxidation during heating and of the dependence of the total mass gain achieved at heating on the heating rate and the mass variation recoding step, was preliminarily realized. The values obtained for this mass gain during heating in stabilized conditions were thereafter used to study the consequences of this first oxidation on the classically determined k_p values. In parallel another type of determination was applied, which led the good original value of k_p, without any dependence on what occurred during heating.