镍基单晶高温合金熔炼工艺优化

Optimization of Melting Process of Nickel-Based Single Crystal Superalloy

采用中频感应熔炼和MgO坩埚制备镍基单晶高温合金,对比研究氩气保护和真空熔炼工艺下合金的氧、氮、硫含量和显微组织,分析了不同工艺的除杂效果,并讨论了真空熔炼过程中延长精炼时间、添加陶瓷过滤网、加入脱氧剂碳等措施对除杂效果的影响。结果表明:氩气保护熔炼镍基单晶高温合金中氧、硫、氮元素的质量分数均高于1×10^(-5),且组织中存在粗大的氧化铝夹杂物;真空熔炼合金中杂质元素质量分数均小于1×10^(-5),同时组织中未发现大尺寸夹杂物;与氩气保护熔炼相比,高真空熔炼有利于降低合金中氮元素的含量;延长精炼时间可促进合金成分均匀化,大功率电磁搅拌加速了氮的脱除速率;添加陶瓷过滤网滤除了合金中大尺寸夹杂物;利用脱氧剂碳和氧的反应来进一步脱氧和脱氮。

The nickel-based single crystal superalloy was prepared by medium frequency induction melting and MgO crucible.The content of oxygen,nitrogen and sulfur and the microstructure of the alloy under argon shielded and vacuum melting process were studied comparatively.The impurity removal effects of different processes were analyzed.The effects of extending refining time,adding ceramic filter and adding deoxidizer carbon in vacuum melting process on impurity removal were discussed.The results show that the mass fractions of oxygen,sulfur and nitrogen in argon shielded melted nickel-based single crystal superalloy were all higher than 1×10^(-5),and there was coarse alumina inclusion in the structure.The mass fraction of impurity elements in vacuum melted alloy was less than 1×10^(-5),and no large-size inclusions were found in the structure.Compared with argon shielded melting,high vacuum melting could reduce the content of nitrogen in the alloy.Extending refining time could promote the homogenization of alloy composition,and high-power electromagnetic stirring could accelerate the removal rate of nitrogen.Adding ceramic filter removed large size inclusions in the alloy.Further deoxygenation and nitrogen removal was carried out by the reaction of deoxidizer carbon and oxygen.