On the High-Temperature Oxidation Behavior of a Ta-Containing Quaternary Co-Base Model Alloy System with γ/γ′-Microstructure - Influence of γ′-Volume Fraction, Surface State, and Heating Condition on Alumina Growth

Hagen S, Weiser M, Kubacka D, Spiecker E, Virtanen S (2020)

Publication Type: Journal article

Publication year: 2020

Journal

Oxidation of Metals Springer Verlag (Germany)

DOI: 10.1007/s11085-020-10003-w

Abstract

The improvement of the high-temperature oxidation resistance remains an ambitious goal for the design of new γ/γ′-strengthened Co-base superalloys, since their oxidation resistance beyond 800 °C still ranks behind their Ni-base counterparts. To better understand the origin of the poor oxidation resistance at higher temperatures, this study focuses on early stages of oxidation of four quaternary (Co-Al-W-Ta system) Co-base model alloys with a two-phase γ/γ′-microstructure and varying γ′-volume fraction at 800 °C, 850 °C and 900 °C. Based on time-resolved isothermal gravimetric analysis (TGA) in synthetic air and detailed electron microscopic analysis, the role of the γ-channel width (or γ′-volume fraction), the surface preparation prior to exposure (polishing versus shot-peening), and the heating conditions (synthetic air versus argon) on protective alumina growth is elucidated. Firstly, for alloys of increased γ′-volume fractions slower oxidation kinetics prevailed. Secondly, the two-phase microstructure was found to decisively affect the propagation of the internal oxidation front at the early stages of oxidation. Thirdly, shot-peening prior to exposure together with a lack of oxygen availability during heating was identified to foster protective alumina growth, accompanied by TCP-phase formation in the substrate. The critical role of a high Al availability in the alloy for a rapid growth of protective alumina and the relating challenges in alloy development regarding, for example, phase stability in this relatively novel Co-base alloy class are discussed in detail.

Authors with CRIS profile

Sebastian Hagen Lehrstuhl für Werkstoffwissenschaften (Korrosion und Oberflächentechnik) Martin Weiser Professur für Werkstoffwissenschaften (Korrosion und Oberflächentechnik) Dorota Kubacka Lehrstuhl für Werkstoffwissenschaften (Mikro- und Nanostrukturforschung) Erdmann Spiecker Lehrstuhl für Werkstoffwissenschaften (Mikro- und Nanostrukturforschung) Sannakaisa Virtanen Professur für Werkstoffwissenschaften (Korrosion und Oberflächentechnik)

Additional Organisation(s)

Interdisziplinäres Zentrum, Center for Nanoanalysis and Electron Microscopy (CENEM) Lehrstuhl für Werkstoffwissenschaften (Mikro- und Nanostrukturforschung)

Related research project(s)

High resolution transmission electron microscopy investigation of the atomic structure of defects and interfaces in single crystal superalloys (A07) (TRR 103) TRR 103: Vom Atom zur Turbinenschaufel - wissenschaftliche Grundlagen für eine neue Generation einkristalliner Superlegierungen Jan. 1, 2012 - Jan. 1, 2015

How to cite

APA:

Hagen, S., Weiser, M., Kubacka, D., Spiecker, E., & Virtanen, S. (2020). On the High-Temperature Oxidation Behavior of a Ta-Containing Quaternary Co-Base Model Alloy System with γ/γ′-Microstructure - Influence of γ′-Volume Fraction, Surface State, and Heating Condition on Alumina Growth. Oxidation of Metals. https://doi.org/10.1007/s11085-020-10003-w

MLA:

Hagen, Sebastian, et al. "On the High-Temperature Oxidation Behavior of a Ta-Containing Quaternary Co-Base Model Alloy System with γ/γ′-Microstructure - Influence of γ′-Volume Fraction, Surface State, and Heating Condition on Alumina Growth." Oxidation of Metals (2020).

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