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观察并研究了X80钢在800~1 200℃下氧化1min的氧化膜以及氧化圆点的形成规律。结果表明:X80管线钢在1 050℃以下具有良好的抗氧化特性,从1 050℃开始整个氧化膜层明显增厚,抗氧化能力下降;在1 000℃以下氧化膜内侧区域存在明显的Si、Cr富集带,温度升高到1 050℃,基体界面开始出现氧化圆点,同时内侧元素富集氧化膜的完整性遭到破坏,此种现象主要与Cr2O3进一步氧化形成CrO3有关。通过热力学和动力学分析发现,低于1 000℃,Si、Cr的氧化物稳定性高,自扩散系数小,利于形成界面处稳定的氧化膜。同时发现,1 050℃属于X80钢氧化质点形成的临界温度,低于此温度主要形成致密的界面氧化膜,它起到明显的抗氧化作用。
The formation of oxide film and oxidation spots of X80 steel oxidized at 800 ~ 1 200 ℃ for 1 min were observed and studied. The results show that the X80 pipeline steel has a good oxidation resistance below 1 050 ℃. From 1 050 ℃, the entire oxide film thickens and its oxidation resistance decreases. At the inner surface of the oxide film below 1 000 ℃, there are obvious Si, Cr enrichment zone, the temperature rises to 1 050 ℃, the substrate interface began to appear oxidation dots, while the integrity of the inner element-enriched oxide film is destroyed, this phenomenon is mainly associated with Cr2O3 further oxidation of CrO3. Thermodynamic and kinetic analyzes show that the oxides of Si and Cr have high stability and low self-diffusion coefficient below 1 000 ℃, which is favorable for the formation of stable oxide film at the interface. At the same time, it is found that 1 050 ℃ belongs to the critical temperature of the formation of X80 steel oxide particles. Below this temperature, a dense interfacial oxide film forms, which plays a significant role in oxidation resistance.