K418合金激光焊接接头组织与裂纹形成原因

Microstructure and Crack Formation in K418 Alloy Laser Welded Joints

通过光学显微镜、扫描电镜、能谱仪等研究了镍基铸造高温合金K418激光焊接接头的组织和焊缝区域成分,分析了接头裂纹产生原因。结果表明:由于激光深熔焊接过程形成的金属蒸气和等离子体在焊缝正面附加热源效应,导致形成大钉头、小钉身的焊缝形貌;焊缝靠近母材的组织为具有一定方向的枝晶组织,且在焊缝与母材交界的不同区域具有锯齿形和光滑过渡两种形貌;焊接过程中,磷、硫和硅元素在晶界偏析形成的低熔点化合物提高了焊接熔池凝固温度范围,增加了焊接过程热裂纹敏感性。

Microstructure and chemical composition of the weld seam of K418 Ni-base superalloy prepared by laser welding were characterized by optical microscopy, scanning electron microscopy, energy dispersive spectrometer. And the weld cracking formation was analyzed. The results show that nailhead shape morphology of weld seam could form as the heat effect of plasma and metal vapor formed during the welding process. Microstructure of dendrites could be observed between weld seam and base metal. There were sawtooth and smoothness shapes at the interface of weld seam and base metal. Temperature range of solidifying was enlarged due to forming low melting point eutectics enriched in P, S and Si. Hot crack sensibility during the welding process was increased.