ABSTRACT The modified HR3C austenitic heat-resistant steels were aged at 650°C and 700°C for up to 3000 h. The effect of Co on microstructure evolution during long-term ageing was investigated using scanning electron microscope and transmission electron microscope. The experimental results showed that a large amount of σ phase precipitated within the grain during long-term ageing. The growth and coarsening of the σ phase were greatly influenced by the temperature. The variation of micro-hardness can be well understood in terms of volume fraction of the σ phase. The activation energy of forming σ phase was calculated by the Johnson–Mehl–Avrami equation and Arrhenius equation. It was found that Co addition can suppress the precipitation of the σ phase. The related mechanism of Co effect is discussed.

中文翻译：

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Co对改性HR3C奥氏体耐热钢长期时效组织演变的影响

摘要 改性 HR3C 奥氏体耐热钢在 650°C 和 700°C 下时效达 3000 小时。使用扫描电子显微镜和透射电子显微镜研究了 Co 对长期时效过程中微观结构演变的影响。实验结果表明，在长期时效过程中，晶粒内析出大量σ相。σ相的生长和粗化受温度影响很大。从 σ 相的体积分数可以很好地理解显微硬度的变化。形成σ相的活化能由Johnson-Mehl-Avrami方程和Arrhenius方程计算。发现Co的添加可以抑制σ相的析出。讨论了Co效应的相关机制。