Growth mechanism of chromia scales on a model Ni-30Cr alloy at high temperatures
Xian Huang, Sophie Bosonnet, Paul Fossati, L. Latu‐Romain, Y. Wouters, J. Aléon, Maximilien Verdier‐Paoletti, François Jomard, Laure Martinelli
Abstract
Oxidation tests with markers and tracers were carried out to investigate the growth mechanism of chromia scale on a model Ni-30Cr alloy. The location of oriented grains characterized by TEM-ASRAR indicated that the scale grew predominantly outward at 800 and 900 °C. Experiments using 18 O and 54 Cr tracers confirmed a cationic transport via grain boundaries at these temperatures, using SIMS and NanoSIMS analyses. In the light of this and previous studies, we propose that the scales grow via diffusion of chromium vacancies at 900 °C and oxygen vacancies at 500 °C. • Marker and tracer experiments for the growth mechanism of chromia on a Ni-30Cr alloy. • Dominant outward growth at 800 and 900 °C characterized by TEM-ASTAR. • Dominant cationic diffusion at 800 and 900 °C found by 18 O tracer experiments. • Grain boundary diffusion at 800 and 900 °C according to 54 Cr tracer experiments. • Growth driven by the diffusion of O vacancies at 500 °C and Cr vacancies at 900 °C.