| Inconel718 superalloy is Ni-Cr-Fe superalloy by age hardening and was designed as a material with high strength and good resistance to low cycle fatigue when used at about 650℃. It is one of the most widely used superalloy for all superalloy production.Inconel718 superalloy with multi-sheet structure will be widely used in aerospace as heat resisting and heat shielding structure due to its lightweight, high strength and stiffness. The most preferred method for forming multi-sheet structure is SPF/DB (Superpalstic Forming and Diffusion Bonding) technology. But the diffusion bonding of Inconel718 superalloy is very difficult to perform because of its high strength in high temperature,distortion difficulty and poor diffusion property. Accordingly, it is in the need of a new method to manufacture the multi-sheet structure of Inconel718 superalloy. Use of laser beam welding as a joining method is being rapidly developed in various industries, from automotive to aerospace, due to its advantages such as high speed, low distortion, low heat input, and narrow width of the fusion zone (FZ) and the heat affected zone (HAZ). In recent years, SPF/DB with LBW (Laser Beam Welding) technology which was presented as extension and supplement of SPF/DB technology has excellent effect on multi-sheet structure of titanium alloy. Inconel718 superalloy's weldablility is generally considered to be good in the superalloys. So, it posses technical competency to manufacture Inconel718 multi-sheet core structure by LBW+SPF composite technology.qThis paper mainly carries superplasticity of Inconel718 superalloy with ultra-fine grain, high temperature plasticity of ultra-fine grain Inconel718 superalloy laser abutting plate, LBW+SPF composite technology of multi-sheet coreboard platestructure for Inconel718 superalloy, heat treating technology of the multi-sheet coreboard plate structure of Inconel718 superalloy, LBW+SPF technology of multi-sheet coreboard cylinder structure of Inconel718 superalloy.Superplasticity of ultra-fine grain Inconel718 superalloy for multi-sheet coreboard structure is studied to preferably supervise superplastic forming of multi-sheet coreboard structure. The ideal superplastic forming temperature for ultra-sine grain in this paper is in 950~965℃. In this temperature range, elongation is higher and flow stress is lower.In order to solve the high temperature forming for the cylinder multi-sheet coreboard with laser butt welds, laser butt plate of Inconel718 superalloy with ultra-fine grain is invesgated. Under simple tension state, tensile direction has great influence on the enlongation of butt plate. At the temperature of 950~980℃, the laser butt plate of Inconel718 superalloy with ultra-fine grain has good ability of free bulging. The relative bulging height is higher than 1.0, which can meet the need for forming of complex parts.The multi-sheet coreboard structures which poss various internal strucutures are manufractured by LBW+SPF composite technology. Through researching effect of weld power and speed on penetration, the laser weld parameters for multi-sheet coreboard structure is confirmed. By controlling the rate of loading for superplastic forming, the multi-sheet coreboard structures have good shape, uniform wall thickness distribution, full forming for the internal structure. The experiment shows that LBW+SPF technology is an appropriate forming technique for multi-sheet coreboard structure of Inconel718 superalloy.In order to enhance multi-sheet coreboard structure used security, the heat treatment technology of multi-sheet coreboard structure is studied. The result shows that Laves precipitation phase which contains higher Nb precipitates in the welding process of Inconel718 superalloy, After SPF process, Nb segregation in the weld is partly dissolved. The heat treatment of solution treatment at 1080℃/30min can make Laves phase dissolve and solve the problem of segregation Nb thoroughly. Grain of Inconel718 superalloy by solution treatment 1080℃grows up greatly and is higher than 150μm. The yield strength compared after superplastic forming decreases to 892MPa. The three-sheet structure has the most anti-compression in the multi-sheet coreboard strucute.The laser welding problem of three-sheet core cylinder structure is settled through clamp apparatus which has internal stay of diametral variation. The three-sheet core cylinder structure is reinforced by spot welding. The three-sheet core cylinder structures by LBW+SPF composite technology have good shape, uniform wall thickness distribution, esthetic appearance of internal structure. The error analysis of cylinder three-sheet core structure shows that actual size of cylinder structure has decination compared to design size because of thermal expansion and shrunk but the decination is small and meets the design requirement.
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