Calculations of parabolic rate constants for metal oxidation

A diffusion driven carburisation combined with a multiaxial continuum creep model to predict random multiple cracking in engineering alloys

“…For metals, different degradation processes [6][7][8][9][10][11][12][13] can result in a time growth relationship that is linear, cubic, parabolic or logarithmic. Only the parabolic case, being the most realistic for engineering components, is considered in this paper.…”

“…It has been shown that environmental damage or oxidation for a range of engineering alloys, versus time, tend to exhibit a parabolic kinetic response [8][9][10][11][12]. The law describes a material property given by the parabolic rate constant, k p , which can change with different materials, temperatures as well as corrosive and oxidation environments described by the relationship:…”

“…Mechanisms such as creep cracking [1][2][3][4][5] and oxidation/carburisation/nitriding [4][5][6][7][8][9][10][11][12][13] have in common a 'rate dependent' damage inducing component. It has been shown that three main categories of damage rate dependencies exist in the oxidation processes.…”

“…The extreme case is linear or accelerating rates of empirical laws damage which can occur at extreme temperatures and environments. The second and third can be described by logarithmic and parabolic relationship [6][7][8][9][10][11][12][13] which essentially describe the rate of damage as continually decreasing with time. In some cases the process can deplete or harden the surface and/or can develop a self-healing/protection mechanism, depending on the type of alloy, environment and temperature and oxidation mode which prevents further surface damage.…”

“…The oxidation damage rate processes can be modelled using oxidation rate processes [4][5] as well as fundamental diffusion or oxidation laws which describe and quantify the rate of damage for different materials [6][7][8][9][10][11][12][13]. When oxidation/carburisation is dominant at the surface the degradation could harden the surface layer which could in turn affect creep damage development.…”