镍基高温合金电子束焊接热影响区微裂纹特征分析

Analysis on the Microfissuring Behavior in the Heat-affected Zone of Electron-beam Welded Nickel-based Superalloy

利用金相分析和扫描电镜对镍基高温合金电子束焊接热影响区微裂纹行为进行了分析。研究发现,熔合线附近的热影响区产生大量液化裂纹和沿晶扩展的固相裂纹。液化裂纹起源于MC碳化物的组份液化而形成的晶界连续或半连续的低熔点共晶液化膜,固相裂纹形成的则是高能电子束流的快速瞬态热冲击效应的直接结果。通过改善焊缝成形和提高焊接线能量有助于减小两类热影响区微裂纹倾向。

The microfissuring behaviors in the heat-affected zone (HAZ) of electron beam (EB) welded nickel-based superalloy GH 4133 have been studied by using analytical scanning electron microscopy (SEM). It is observed that considerable liquation microcracks and some other microfissures called solid-state microcrack initiate in the regions nearby the fusion line and propagate across the grain boundary. The microstructure observation in the microfissures suggests the liquation microcrack results from grain boundary liquation by constitutional liquation of MC carbides and formation of continuous and/or semi-continuous low melting liquid films, however, the occurrence of the solid-state microcracks can be attributed to the effect of ultrafast transit thermal shock introduced by high energy electron beam. Minimal the tendency of microcracks can be obtained by improving the shape of weld pool and enhancing the welding energy input.