Abstract

Thin-walled castings made from Cr–Ni austenitic steels offer a combination of light weight of a near-net component with significant high temperature corrosion protection by forming a surface oxide layer. However, above critical service conditions (temperature, atmosphere, thermal cycling), oxidized surface can result in intensive surface degradation due to scale spallation. Scale spallation can decrease the wall thickness which could be detrimental to the in-service life of thin-walled castings. Experiments and stochastic simulations of spallation assisted oxidation were performed with three cast austenitic heat-resistant steels having different Cr–Ni concentrations at temperatures between 900 and 1000 ℃ on air and water vapor containing combustion atmosphere. The recorded specimen and spalled scale weight together with SEM and TEM analysis were used to predict the oxidation constant to form adherent layer and spallation intensity. Three oxidation modes, including oxidation controlled by diffusion with forming a strongly adherent to steel surface multi-layered scale, spallation assisted oxidation, and oxidation with additional partial vaporization of scale components in the water vapor environment were distinguished. It was revealed that the Cr and Ni concentrations moved temperature boundaries between these surface degradation mechanisms depending on the exposed oxidation environment. Our approach is aimed to alleviate an appropriate alloy selection for service conditions.

Department(s)

Materials Science and Engineering

Comments

U.S. Department of Energy, Grant DE-EE0008458

Keywords and Phrases

Austenitic steel; Oxidation; Spallation

International Standard Serial Number (ISSN)

1573-4889; 0030-770X

Document Type

Article - Journal

Document Version

Final Version

File Type

text

Language(s)

English

Rights

© 2023 Springer, All rights reserved.

Publication Date

01 Jan 2022

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