Abstract
The effects of surface preparations on oxidation kinetics and oxide scale morphology for the commercially available Ni-based superalloy IN 713C have been investigated. The ground and polished samples were exposed in air at 800-1100 °C. The ground specimens were found to demonstrate lower oxidation kinetics compared to those after polishing. The grinding also affected the oxide scale morphology, resulting in a protective alumina scale, while the polished samples developed Ni-/Cr-rich mixed oxides on the surface. Better oxidation resistance of the ground surfaces is related to a higher concentration of defects in the near-surface region introduced by cold working. These defects facilitate the outward transport of the scale-forming element Al and thus are beneficial for protective oxidation. The oxidation mechanism at lower temperatures was introduced. The model based on the generalized Darken method and multiphase approximation was proposed.
Highlights
Over the decades, high-temperature metallic materials such as Ni-based alloys have been optimized to provide high strength at room as well as at elevated temperatures (Ref 1)
The aim of the present work is to investigate the effect of surface preparation on the oxidation resistance of Ni-based superalloy IN 713C between 800 and 1100 °C exposed in laboratory air
A thin alumina scale is formed on the ground samples oxidized at both temperatures
Summary
High-temperature metallic materials such as Ni-based alloys have been optimized to provide high strength at room as well as at elevated temperatures (Ref 1). The latter is achieved by alloying with aluminum to form stable strengthening precipitates such as c¢. Due to the limited Cr and/or Al content, numerous high-temperature construction materials are termed as ‘‘marginal’’ alumina or chromia formers (Ref 3). This implies that the ability of the alloy to form protective scales strongly depends on exposure conditions, i.e., temperature, gas composition, heat treatment, surface preparation, etc. Another way to promote protective external oxide scaling on high-temperature alloys without changing the material composition and/or manufacturing technology is mechanical surface treatment proposed in the present work
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