Characterization of the Microstructures and the Cryogenic Mechanical Properties of Electron Beam Welded Inconel 718
Characterization of the Microstructures and the Cryogenic Mechanical Properties of Electron Beam Welded Inconel 718
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DOI：
10.1007/s11661-015-3269-6
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发表时间：
2016-02-01
影响因子：
2.8
通讯作者：
Hong, Hyun Uk
中科院分区：
文献类型：
--
作者：
Kwon, Soon Il;Bae, Sang Hyun;Hong, Hyun Uk
研究了厚度为10 mm的Inconel 718铸造和锻造高温合金电子束（EB）焊接接头的显微组织和低温力学性能，并与钨极氩弧焊（GTA）接头进行了对比。当电子束焊接线能量低于250 J/mm时，在电子束焊缝的铸侧热影响区（HAZ）形成液化微裂纹。热影响区液化微裂纹似乎与晶界处初生NbC碳化物的成分液化有关。与GTA焊接工艺相比，电子束焊接产生具有上级显微组织的焊缝，由于快速冷却速率，呈现与Laves相的尺寸和分数减小相关的细枝晶结构。这一结果是在77 K（-196 A摄氏度）下电子束焊接的上级机械性能的原因。发现两个焊缝中的Laves颗粒为裂纹萌生和扩展提供了优先位点，导致77 K（-196 A ℃）下的夏比冲击韧性显著降低。从枝晶臂间距、Laves相尺寸和断裂Laves相产生的裂纹前位错结构等方面讨论了两种焊缝夏比冲击裂纹的萌生和扩展。
The microstructures and the cryogenic mechanical properties of electron beam (EB) welds between cast and forged Inconel 718 superalloys with a thickness of 10 mm were investigated in comparison with gas tungsten arc (GTA) welds. EB welding with a heat input lower than 250 J/mm caused the formation of liquation microfissuring in the cast-side heat-affected-zone (HAZ) of the EB welds. HAZ liquation microfissuring appeared to be associated with the constitutional liquation of primary NbC carbides at the grain boundaries. Compared with the GTA welding process, the EB welding produced welds with superior microstructure, exhibiting fine dendritic structure associated with the reduction in size and fraction of the Laves phase due to the rapid cooling rate. This result was responsible for the superior mechanical properties of the EB welds at 77 K (-196 A degrees C). Laves particles in both welds were found to provide the preferential site for the crack initiation and propagation, leading to a significant decrease in the Charpy impact toughness at 77 K (-196 A degrees C). Crack initiation and propagation induced by Charpy impact testing were discussed in terms of the dendrite arm spacing, the Laves size and the dislocation structure ahead of the crack arisen from the fractured Laves phase in the two welds.