Abstract
The 3-sheet structure of Inconel 718 superalloy will be used in flying vehicles as heat resisting and shielding structure due to its lightweight, high strength and stiffness. The 3-sheet structure of Inconel 718 superalloy processed by LBW/SPF (laser beam welding/superplastic forming) technology exhibited good configuration and uniform thickness distribution. The LBW parameters for 3-sheet structure were as follows: Pulse frequency was 32 Hz, impulse duration 3 ms, peak power per pulse 4500 W, and welding speed 180 mm/min. The SPF parameters were as follows: Temperature T=965°C, forming pressure P=4.2 MPa, and forming time t=130 min. The microstructure in weld fusion zone was constituted of austenite dendritics and Laves phase precipitated in interdendritics. After the SPF process, austenite dendritics in the weld fusion became coarser and most of Laves phases were dissolved and turned into δ precipitated phase, but a few of Laves phases were still reserved. And Nb concentration in dendritics increased to 5.42% compared to 2.82% in as-weld condition. Weld metal Vickers-hardness increased from 331.63 in as-weld condition to 391.74 in post-SPF condition which was closed to the base material Vickers-hardness of post-SPF. Grain size of base material grew slightly and an amount of precipitated phase appeared in the base material undergoing SPF process. The tensile test results of base material showed that tensile strength increased obviously and the ductility decreased slightly after SPF process. Load response test results indicated that the 3-sheet structure possessed good resistance to compression and bending load. Accordingly, the LBW/SPF technology is an appropriate forming technique for the 3-sheet structure of Inconel 718 superalloy.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Han W B, Zhang K F, Wang G F, et al. Research on microstructures and properties of diffusion bonding joints for Inconel 718 superalloy. Mater Sci Technol, 2005, 3(13): 308–311
Dong J X, Xie X S, Zhang S H. Coarsening behavior of γ precipitates in modified Inconel 718 superalloy. Scripta Mater, 1995, 33(12): 1933–1939
Ram G D J, Reddy A V, Rao K P, er al. Control of laves phase in Inconel 718 GTA welds with current pulsing. Sci Technol Weld Joining, 2004, 9(5): 390–398
Cam G, Kocak M. Progress in joining of advanced materials. Int Mater Rev, 1998, 43(1): 1–44
Li Z Q, Li X H. The application of SPF/DB combined with welding technologies. Mater Sci Forum, 2007, 551–552: 49–54
Mullins W W, Sekerka R F. Stability of a planar interface during solidification of a dilute binary alloy. J Appl Phys, 1964, 35(2): 444–451
Ram G D J, Reddy A V, Rao K P, et al. Microstructure and tensile properties of Inconel 718 pulsed Nd-YAG laser welds. J Mater Process Technol, 2005, 167(1): 73–82
Thompson R G, Cassimus J J, Mayo D E, et al. The relationship between grain size and microfissuring in alloy 718. Weld J, 1985, 64(4): 91s–96s
Radhakrishna C H, Rao K P. The formation and control of Laves phase in superalloy 718 welds. J Mater Sci, 1997, 32(8): 1977–1984
Author information
Authors and Affiliations
Corresponding author
Additional information
Supported by the National Natural Science Foundation of China (Grant No. 50672106) and the Intellectual Innovation Project of the Chinese Academy of Sciences (Grant No. KJCX3-SYW.No.12)
Rights and permissions
About this article
Cite this article
Qu, F., Zhang, K. 3-sheet structure of Inconel 718 superalloy processed by LBW/SPF and its load response. Sci. China Ser. E-Technol. Sci. 52, 2237–2244 (2009). https://doi.org/10.1007/s11431-009-0217-y
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11431-009-0217-y