Papers by Keyword: High Energy Beam Welding

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Authors: Kyung Ju Min, Jong Hoon Yoon, Joon Tae Yoo, Ho Sung Lee
Abstract: Alloy IN718 is a nickel based precipitation hardened material and it has the necessary strength over a range of temperatures which includes the operating range for many rocket propulsion systems and jet engines. This performance is accomplished by a combination of solid-solution strengthening, precipitation strengthening and grain-boundary strengthening. However, it is common for precipitation hardened nickel based superalloys to have a problem of post-weld cracking. In this study, several welding processes are investigated to obtain the optimum welding method of IN718 for elevated temperature forming. These include LBW(Laser Beam Welding), EBW(Electron Beam Welding), HIP(hot isostatic pressing), and solid state diffusion bonding. The result shows that the LBW specimen performs the highest formability at 980°C so that this process can be applied to superplastic forming of IN718 sheet. It is demonstrated that the elevated temperature superplastic forming of nozzle extension with internal cooling channels was possible with laser beam welded IN718 sheet.
Authors: G. Wang, Kai Feng Zhang, Wen Bo Han, D.Z. Wu, C.W. Wang
Abstract: The superplastic bulging capabilities of Ti-6Al-4V butt-welded plates with 0.8mm in thickness with high energy beam welding methods namely plasma arc welding (PAW), electron beam welding (EBW) and laser beam welding (LBW) are studied in virtue of superplastic bulging tests. Superplastic bulging tests are performed at the superplastic forming temperature 925°C under 1MPa gas pressure. The superplastic bulging capability is represented by the maximum relative bulging height h after fracture. Experimental results suggest that all of butt-welded plates with high energy beam welding methods possess good superplastic bulging capability. Among them, the maximum relative bulge height of LBW is the highest, that of EBW is slightly lower and that of PAW is the lowest. The higher the input energy density is, the bigger the bulge height will be. Furthermore their microstructure evolutions of various weld metals during superplastic bulging were systematically analyzed via metallographical tests. The relation between the microstructure of weld metal and its superplasticity is found. Metallographical analysis shows that the microstructure of Ti-6Al-4V weld metal with high energy beam welding methods is composed of fine acicular martensite. The higher the input energy density is, the finer the martensite structure will be. Upon heating, this martensite changes to a basketweave-like structure and upon bulging, the martensite structure have the trend of transforming to fine equiaxed grain. This can explained the reason why the Ti-6Al-4V butt-welded plates with high energy beam welding methods have excellent superplastic bulging capability.
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