As part of round robin testing, specimens of commercial alloys 316, 120, 625, and 740 were exposed to 20 MPa research grade CO2 at 700 °C for up to 1500 h. The first set of specimens had higher mass gain likely due to impurities not flushed from the autoclave at startup. After this issue was corrected, an identical set of specimens exhibited lower mass gains for both the Fe- and Ni-based alloys. The differences in reaction products were characterized to understand the effect of impurities under these conditions. As suggested by the mass change, thicker oxides were formed in each case, primarily for the Fe-based alloys. For the Ni-based alloys, the difference was primarily in the transient stage of oxidation with no change in rate constant. Alloy 120 exhibited increased internal attack, and differences in the scale phases formed were characterized to better understand the effect of impurities. Alloy 740 primarily exhibited a greater depth of internal attack in the first run.

中文翻译：

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杂质对 700 °C 超临界 CO2 中合金行为的影响

作为循环测试的一部分，商用合金 316、120、625 和 740 的样品在 700 °C 下暴露于 20 MPa 研究级 CO2 中长达 1500 小时。第一组样品具有较高的质量增益，这可能是由于在启动时没有从高压釜中冲洗掉杂质。纠正此问题后，对于 Fe 基和 Ni 基合金，一组相同的试样显示出较低的质量增加。表征反应产物的差异以了解杂质在这些条件下的影响。正如质量变化所表明的那样，在每种情况下都会形成更厚的氧化物，主要是铁基合金。对于镍基合金，差异主要在于氧化的瞬态阶段，速率常数没有变化。合金 120 表现出增加的内部攻击，并表征形成的水垢相的差异，以更好地了解杂质的影响。合金 740 在第一次运行中主要表现出更大的内部攻击深度。