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Vol.54, No.1, 29 ~ 40, 2016
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| Title |
| Effect of Post-Weld Heat Treatment on the Microstructure and the Cryogenic Mechanical Properties of Electron Beam Welded Cast Inconel 718 |
| 권순일 Soon Il Kwon , 도정현 Jeong Hyeon Do , 조창용 Chang Yong Jo , 홍현욱 Hyun Uk Hong |
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| Abstract |
| Effects of post-weld heat treatment (PWHT) on the microstructure evolution and the mechanical properties at -196 ℃ have been investigated with electron beam (EB) welds of cast Inconel 718. Coarse Laves particles in EB fusion zones after conventional PWHTs provided a preferential site for crack initiation, leading to a significant decrease in cryogenic Charpy impact toughness. A modified PWHT, which was highlighted as higher-temperature solution treatment followed by slow cooling to 980 ℃, was designed to ensure a sufficient micro-plastic region ahead of crack tip by a significant reduction of the Laves size and fraction. The EB weld after the modified PWHT exhibited no blocky Laves particles. Instead NbC with a size of 200~300 nm were observed. This modified PWHT led to 1.7 times higher CVN impact toughness than base metal. The cryogenic mechanical properties of EB welds are discussed in terms of dendrite arm spacing, the Laves size and fraction. |
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| Key Words |
| alloys, welding, microstructure, transmission electron microscopy, TEM, cryogenic mechanical properties |
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