Investigation of the Fundamental Processes in the Internal Oxidation of Binary and Ternary Iron Based Alloys at Elevated Temperatures
In order to develop a fundamental understanding, binary and ternary model alloys (for instance, Fe‑Mn, Fe-Cr etc.) are considered. Significant focus will be given to the oxidation kinetics i.e., monitoring of the mass gain during isothermal oxidation using a thermo‑gravimetric balance (TG). The partial pressure of oxygen during the experiments is kept just below the equilibrium pressure for FeO/Fe. As the mass changes during internal oxidation are very low, errors from buoyancy effects in a standard set-up are in the same range as the mass change to be investigated. Hence, a novel under-pressure TG set-up was developed and applied here. In this under-pressure TG the same gas composition of water vapor and hydrogen are used, but the inert carrier gas N2is omitted, significantly decreasing buoyancy effects. Thus the mass gain measurement is carried out with so far unequaled accuracy.
Furthermore, the role of elemental segregation to the grain boundaries on grain boundary oxidation was investigated. The results will be discussed also on the basis of earlier simulation work .
 M. Auinger, S. Borodin, S. Swaminathan and M. Rohwerder, Materials Science Forum 696 (2011) 76-81