Abstract
A straightforward conceptual tool for discriminating between different oxide scaling processes deviating from the parabolic standard model is formulated. Grain boundary diffusion-controlled oxide scaling is generalized to include lateral grains coarsening. Building on traditional Wagner theory, attenuation of rates of inwards growing oxides owing to the gradual loss of grain boundary density is revisited. Two viable cases are identified. One has the rate of grain boundary density loss to be independent of the rate of oxide growth, while the second case takes the two instantaneous rates to be equal. Simple parabolic–logarithmic and superparabolic–cubic expressions are arrived at for the two cases, respectively. Usefulness is demonstrated by applying the models to published experimental data from 1990 to date. Upon arrival at the superparabolic–cubic behaviour, a generic mathematical form analogous to a ‘spring force’ attenuating the scale growth was identified. ‘Parabolic’, ‘cubic’ and ‘logarithmic’ scaling emerges as limiting cases.
Highlights
For several decades, the outstanding properties of oxide dispersion strengthened alloys have served as a vehicle for fundamental research at the forefront of industrial materials development of relevance to chemical engineering and energy conversion processes [1, 2]
Below we explore to what extent grain boundary transport alone—as attenuated by change of grain boundary density exclusively taking place at the mobile reaction zone—may suffice to describe experimentally observed oxide scale growth kinetics
By comparing to the experimental literature, here we demonstrate the possible validity of the two fundamental assumptions—the predominance of grain boundary transport and the location of grains coarsening processes to the mobile reaction zone, vide supra—as well as the potential usefulness of the emerging conceptual understanding
Summary
The outstanding properties of oxide dispersion strengthened alloys have served as a vehicle for fundamental research at the forefront of industrial materials development of relevance to chemical engineering and energy conversion processes [1, 2]. The efficient generic high-temperature oxide scaling of aluminaforming ODS alloys—i.e. slow growing and well adhering—apparently contradicts their complex and diverse compositions and textures. Oxidation of Metals (2019) 91:55–75 providing the third element effect [3,4,5,6]—are tuned to achieve the sought near-ideal long-term scaling property. Additional fine-tuning, mainly aiming at improved scale/alloy adhesion, is achieved by the so-called reactive elements—e.g. Y, La, Zr, Hf—often appearing as submicron oxide particles in the ODS alloy [7, 8]. The origins of often near-ideal oxidation properties at high temperatures are increasingly being unravelled and revisited by employing state-of-the-art analysis on the nanoscale in conjunction with atomistic first-principles modelling [11]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
