Early stages of high-temperature oxidation of Ni- and Co-base model superalloys: A comparative study using rapid thermal annealing and advanced electron microscopy

A novel approach based on rapid thermal annealing and advanced electron microscopy is used to elucidate the differences in early stages of high-temperature oxidation of Ni- and Co-base superalloys at 900 degrees C. STEM-EDX results obtained for two model superalloys with exactly the same alloying additions demonstrate the individual role of the gamma and gamma' phase during initial oxidation. Observed differences in Al2O3 formation can be directly correlated to changes in the partitioning behavior and the type of defects introduced during oxidation, depending on the base element. Explanations for the worse oxidation resistance of gamma'-strengthened Co-base superalloys are proposed.

Automated summary

A novel approach using rapid thermal annealing and advanced electron microscopy was used to investigate the differences in early stages of high-temperature oxidation of Ni- and Co-base superalloys at 900 degrees C. STEM-EDX results showed the distinct roles of the gamma and gamma' phase during initial oxidation, and differences in Al2O3 formation were directly linked to changes in partitioning behavior and defect types introduced during oxidation, depending on the base element. Explanations for the inferior oxidation resistance of gamma'-strengthened Co-base superalloys were proposed.