Predicting Internal Oxidation: Building on the Wagner Model
| Periodical | Materials Science Forum (Volume 696) |
|---|---|
| Main Theme | High-Temperature Oxidation and Corrosion 2010 |
| Edited by | Toshio Maruyama, Masayuki Yoshiba, Kazuya Kurokawa, Yuuzou Kawahara and Nobuo Otsuka |
| Pages | 1-11 |
| DOI | 10.4028/www.scientific.net/MSF.696.1 |
| Citation | David J. Young, 2011, Materials Science Forum, 696, 1 |
| Online since | September, 2011 |
| Authors | David J. Young |
| Keywords | Carburization, Cellular Precipitation, Diffusion, Kinetic, Low Stability Precipitates, Nitridation |
| Price | US$ 28,- |
Wagner’s 1959 diffusion model of the internal oxidation process provided a method of predicting the rate at which a binary alloy was penetrated by dissolved oxygen as it precipitated the more reactive (but dilute) alloy component. Parabolic kinetics were predicted to depend on oxygen permeability in the unreacted alloy solvent and also, in cases where the reactive component was sufficiently mobile, the diffusion coefficient of the latter. The model has proven very successful, but is restricted to single oxidant-binary alloy systems, in which the precipitated oxide has extremely low solubility. This paper reviews recent results on a number of internal precipitation processes which cannot be described with the Wagner theory. These include formation of low stability carbides and nitrades; internal precipitation driven by multiple oxidants; the templating effects of prior precipitates on subsequently formed corrosion products; cellular precipitation morphologies; internal interface diffusion effects; volume changes in the reaction zone and the effects upon them of simultaneous external scaling.
