镍基高温合金Inconel 740H焊接凝固过程元素偏析行为和组织演变研究

Investigation on Elements Segregation and Microstructure Evolution during Weld Solidification of Nickel-based Superalloy Inconel 740H

采用扫描电镜和能谱仪等分析方法以及热力学计算模拟研究了镍基合金Inconel 740H焊丝焊接GH750过热器管时的焊接凝固行为和焊缝金属的组织变化。结果表明:Inconel 740H合金焊丝焊接凝固时,焊缝金属中存在明显的合金元素偏析,Ti和Nb元素是主要的偏析元素,且在凝固组织的枝晶间偏析,元素偏析的分析结果和热力学模拟结果一致。焊接接头在760℃和800℃时效3000 h后,因Ti和Nb元素在枝晶间的偏析,导致Inconel 740H凝固组织枝晶干处析出γ'相数量少,枝晶间处析出γ'相数量明显多,且已析出少量的η相。

The solidification process and microstructure evolution of the weld metal in the GH750 superheater tube joints welded with Nickel-based welding wire Inconel 740H were investigated by means of scanning electron microscope(SEM),energy dispersive spectrometer(EDS)and thermodynamic calculation.Results show that obvious segregation exists in the weld metal during solidification process when Inconel 740H welding wire is used.Titanium and Niobium are the major segregation elements,and the segregation generally happens in the interdendritic region.The analysis results of element segregation agree well with those of thermodynamic calculation.After being aged for 3000 h at 760℃and 800℃,fewγ'phases precipitate on the dendritic trunk while moreγ'phases precipitate in the interdendritic region of solidified Inconel 740H,where a small quantity ofηphases are observed.