Anti-corrosion behavior of Fe–Cr alloys at elevated temperature is greatly influenced by the protective nature of oxide scale formed on them. However, precipitates formed underneath the scale can affect the diffusion of reactive elements, growth mechanism and failure mechanism of oxide film. Here, we elucidate the precipitation mechanism of Laves phase in the vicinity of oxide film during oxidation at 950–1050 °C in air. Two types of automotive exhaust manifold-used ferritic stainless steels were designed by replacing Mo with different contents of W and adding small content of Ce. By systematic investigations of the precipitates in the vicinity of steel/oxide interface, we conclude that Laves phase precipitated near the oxide film is related to the selective oxidation of chromium, which is dramatically different from conventional precipitation mechanism. Nb was localized at the interface due to rejection from the growing Cr 2 O 3 scale, which promoted the formation of Laves phase. The experimental steels were characterized by excellent oxidation resistance and Ti–rich oxide formed in the internal oxidation zone that hindered the further diffusion of oxygen.

中文翻译：

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Laves相在铁素体不锈钢氧化膜附近的沉淀行为：选择性氧化诱导沉淀

Fe-Cr合金在高温下的抗腐蚀行为很大程度上受其上形成的氧化皮的保护性质的影响。然而，在氧化皮下形成的沉淀物会影响反应元素的扩散、氧化膜的生长机制和失效机制。在这里，我们阐明了在空气中 950-1050 °C 氧化过程中 Laves 相在氧化膜附近的析出机制。设计了两种汽车排气歧管用铁素体不锈钢，采用不同W含量替代Mo和添加少量Ce。通过对钢/氧化物界面附近析出物的系统研究，我们得出结论，在氧化膜附近析出的 Laves 相与铬的选择性氧化有关，这与传统的沉淀机制有很大的不同。由于不断增长的 Cr 2 O 3 鳞片的排斥，Nb 被定位在界面处，这促进了 Laves 相的形成。实验钢的特点是优异的抗氧化性和在内部氧化区形成的富钛氧化物，阻碍了氧的进一步扩散。