焊后热处理对高温合金异种材料焊接组织的影响

针对含有较多合金元素的镍基单晶高温合金熔焊焊接性能较差的问题,采用扫描电子显微镜、背散射衍射分析和显微硬度仪等手段,研究了镍基单晶高温合金DD8和钴基等轴晶K640M的氩弧焊焊接显微组织特征.结果表明,焊接后接头形成定向柱晶区、熔合区和母材区.对实验合金进行焊后热处理后发现,熔合区和定向柱晶区中γ相发生长大,且Co等元素的分布趋于均匀,焊接残余应力的存在导致个别位置出现再结晶现象.热处理前后接头内显微硬度无明显变化.

Influence of post-welding heat treatment on welding microstructure of superalloy dissimilar materials

In order to solve the problem that the fusion welding performance of Ni based single crystal superalloys containing high content of alloying elements is poor, the microstructural characteristics of Ni based single crystal superalloy DD8 and Co based equal axis crystal superalloy K640M after the argon arc welding were studied with such means as scanning electron microscope （SEM）, electron back scattering diffraction （EBSD） analysis and microhardness tester. The results show that three zones including the directional columnar grain zone, fusion zone and matrix zone form in the welding joint. After the post welding heat treatment （PHT）, it is found that the γ phase in both fusion zone and directional columnar grain zone grows and the distribution of such elements as Co tends to be uniform. Due to the existence of residual welding stress, the recrystallization can be observed in some area. The microhardness of welding joint before and after PHT has no obvious difference.