Details of the desulfurization for molten Ni-base superalloys containing Al using solid CaO have been investigated, and the formula that explains the reaction rate has been developed. A cylindrical CaO rod was inserted into 500 g molten Ni-base superalloy TMS-1700 (MGA1700) containing 200 ppm S and held for a certain period at 1600 °C in each experiment. Sulfur content in the melt decreased with the increasing holding time of the CaO rod. Results of electron probe microanalysis show that Ca, O, S, and Al distribute in the same part of the melt/CaO interface as well as the particle boundaries of the CaO rods. The distribution of these elements suggests that CaO reacted with S in the melt to generate CaS, and Al reacted with O and CaO to form calcium aluminate slag. The desulfurization rate formula was obtained by the assumption that the rate-controlling process of the desulfurization is S diffusion through the generated layer composed of CaS and calcium aluminate slag. This formula expresses the amount of S in the melt by the diffusion term with the effective diffusion coefficient, which was obtained from the experimental results. Moreover, the time required for the desulfurization of 2 kg molten Ni-base superalloy PWA1484 using a CaO crucible, was calculated by this desulfurization rate formula which resulted in fair agreement with the actual result.

中文翻译：

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含铝熔融镍基高温合金中固体 CaO 的脱硫模型

研究了使用固体 CaO 对含铝的熔融镍基高温合金进行脱硫的细节，并开发了解释反应速率的公式。在每个实验中，将圆柱形 CaO 棒插入 500 克含有 200 ppm S 的熔融镍基高温合金 TMS-1700 (MGA1700) 中，并在 1600 °C 下保持一段时间。熔体中的硫含量随着 CaO 棒保持时间的增加而降低。电子探针微量分析结果表明，Ca、O、S 和 Al 分布在熔体/CaO 界面的同一部分以及 CaO 棒的颗粒边界。这些元素的分布表明，CaO 与熔体中的 S 反应生成 CaS，Al 与 O 和 CaO 反应生成铝酸钙渣。脱硫速率公式是通过假设脱硫的速率控制过程是S通过由CaS和铝酸钙渣组成的生成层扩散而得到的。该公式通过具有有效扩散系数的扩散项来表示熔体中 S 的含量，这是从实验结果中得出的。此外，使用CaO坩埚对2kg熔融Ni基高温合金PWA1484进行脱硫所需的时间，通过该脱硫率公式计算得到，与实际结果基本吻合。这是从实验结果中得出的。此外，使用CaO坩埚对2kg熔融Ni基高温合金PWA1484进行脱硫所需的时间，通过该脱硫率公式计算得到，与实际结果基本吻合。这是从实验结果中得出的。此外，使用CaO坩埚对2kg熔融Ni基高温合金PWA1484进行脱硫所需的时间，通过该脱硫率公式计算得到，与实际结果基本吻合。