Over a decade ago, γ′-strengthened Co-base alloys were introduced as potential replacement for conventional Ni-base Superalloys. Insufficient resistance against high-temperature oxidation restricts the number of possible applications. The present study contributes to the understanding of elementary mechanisms such as material transport during extensive oxide scale formation on γ/γ′ Co-base alloys to explain their inferior oxidation behaviour. A clear dependency of the scale growth kinetics on W content and oxidation temperature is demonstrated by thermogravimetry and subsequent analysis of cross-sections. By means of electron backscattered diffraction (EBSD), the evolution of microstructures in the outer oxide layers were examined depending on the oxidation temperature. Sequential exposure of samples in ¹⁶O₂- and ¹⁸O₂-containing atmospheres proved counter-current material transport. The combination of focused ion beam (FIB) and secondary ion mass spectroscopy (SIMS) visualised the formation of new oxide phases mainly on the outer and inner interface of the oxide scale. An elaborate review of available transport paths for oxygen is given during the discussion of results. All experimental findings were combined to a coherent explanation of the inferior oxidation resistance of this relatively new class of high-temperature materials at temperatures above 800 °C.

十多年前，人们引入了γ '强化的Co基合金，以替代传统的Ni基高温合金。耐高温氧化性不足，限制了可能的应用数量。本研究有助于了解基本机理，例如在γ / γ上形成大量氧化皮时的材料传输'钴基合金来解释其次等的氧化行为。通过热重分析和随后的横截面分析证明了鳞片生长动力学对W含量和氧化温度的明显依赖性。借助于电子背散射衍射（EBSD），根据氧化温度检查了外部氧化物层中微观结构的演变。样品在¹⁶ O _2-和¹⁸ O _2中的顺序暴露含气氛证明了逆流物质的运输。聚焦离子束（FIB）和二次离子质谱（SIMS）的结合可视化了主要在氧化物水垢的内外界面上形成新的氧化物相。在讨论结果的过程中，详细审查了可用的氧气传输路径。所有的实验结果都被结合在一起，对这种相对较新的高温材料在800°C以上的温度下的抗氧化性进行了较明确的解释。