钴基高温合金GH188中镧化物类型及元素Mg晶界偏聚的研究

使用俄歇电子谱仪（ＡＥＳ）、透射电镜结合能谱仪（ＥＤＡＸ）及扫描电镜等分析仪器，研究了用双真空（真空感应熔炼＋真空自耗重熔）工艺生产的钴基高温合金ＧＨ１８８中稀土镧化物的析出形貌与类型以及添加的微量元素Ｍｇ晶界偏聚的特性。研究结果表明，采用双真空工艺重熔后，合金中的镧化物呈不均匀分布，导致以它为形核点析出的部分碳化物也分布不均，使其弥散强化效果变差。该合金中的镧化物主要有Ｌａ２Ｏ３，Ｌａ２Ｏ２Ｓ，ＬａＯＳ２，Ｌａ２Ｓ３等类型。另外，微量元素Ｍｇ在合金中的晶界偏聚较为明显，这将降低合金的热加工性。因此，ＧＨ１８８合金中应限制元素Ｍｇ的含量或不加Ｍｇ

Study on Lanthanide Precipitate Type and Magnesium Segregation to Grain Boundary in Cobalt-Base Superalloy GH188

The precipitatetypes and morphology of lanthanide, and the segregation behaviour of magnesium to grainboundaries in VIM+VAR produced cobalt-base superalloy GH188 have been studied by means ofAuger electron spectroscopy, transmission and scanning electron microscopy with EDAXanalysis. It has been proved that during the VAR process there precipitate someunevenly-distributed lanthanides, which subsequently makes an uneven carbide distributionowing to these carbides nucleating at or around the lanthanide, leading to a lowerdispersion-strengthening effect of the carbide. There also exist several types oflanthanides which mainly include La₂O₃, La₂O₂S,LaOS₂ and La₂S₃. Additionally, minute magnesium atom hasapparently segregated on grain boundary, which will lower the hot working property of thisalloy instead of strengthening the grain boundary. Therefore, the quantity of addedmagnesium should be controlled or completely limited in superalloy GH188.