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http://dx.doi.org/10.5781/KWJS.2013.31.6.50

A Study on Microstructures and Cryogenic Mechanical Properties of Electron Beam Welds between Cast and Forged Inconel 718 Superalloys for Liquid Rocket Combustion Head  

Hong, Hyun-Uk (Department of Materials Science and Engineering, Changwon National University)
Bae, Sang-Hyun (Department of Materials Science and Engineering, Changwon National University)
Kwon, Soon-Il (Department of Materials Science and Engineering, Changwon National University)
Lee, Je-Hyun (Department of Materials Science and Engineering, Changwon National University)
Do, Jeong-Hyeon (High Temperature Materials Research Group, Korea Institute of Materials Science)
Choi, Baig-Gyu (High Temperature Materials Research Group, Korea Institute of Materials Science)
Kim, In-Soo (High Temperature Materials Research Group, Korea Institute of Materials Science)
Jo, Chang-Yong (High Temperature Materials Research Group, Korea Institute of Materials Science)
Publication Information
Journal of Welding and Joining / v.31, no.6, 2013 , pp. 50-57 More about this Journal
Abstract
Characterization of microstructures and cryogenic mechanical properties of electro beam (EB) welds between cast and forged Inconel 718 superalloys has been investigated. Optimal EBW condition was found in the beam current range of 36~39 mA with the constant travel speed of 12 mm/s and arc voltage of 120 kV for 10 mm-thick specimens. Electron beam current lower than 25 mA caused to occur the liquation microfissuring in cast-side heat affected zone (HAZ) of EB welds. The HAZ liquation microfissure was found on the liquated grain boundaries with resolidified ${\gamma}/Laves$ and ${\gamma}/NbC$ eutectic constituents. EBW produced welds showing a fine dendritic structure with relatively discrete Laves phase due to fast cooling rate. After post weld aging treatment, blocky Laves phase and formation of ${\gamma}^{\prime}+{\gamma}^{{\prime}{\prime}}$ strengtheners were observed. Presence of primary strengthener and coarse Laves particles in PWHT weld may cause to reduce micro-plastic zone ahead of a crack, leading to a significant decrease in Charpy impact toughness at $-196^{\circ}C$. Fracture initiation and propagation induced by Charpy impact testing were discussed in terms of the dislocation structures ahead of crack arisen from the fractured Laves phase.
Keywords
Superalloy; Electron beam welding; Cryogenic; Microfissure; Fracture toughness; Laves; Dislocation;
Citations & Related Records
Times Cited By KSCI : 1  (Citation Analysis)
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