Research On Technic Of Vacuum Diffusion Bonding Of GH4169 Alloy

Diaphragm foil device as rockets elastic element, were often limited by their own shortcomings. In order to use the diaphragm box to instead of diaphragm foil, the teshnics of GH4169 alloy direct vacuum diffusion bonding and indirect diffusion bonding with Cu foil or Ni foil were investigated, including the effects of the surface state, joining temperature, holding time and diffusion pressure. With the help of SEM, EDS, XRD, nanoindentation and other analysis and detection methods, the effects of process parameters on the joint interface structure and properties were analysised.Direct vacuum diffusion bonding was adopted to connect GH4169 alloy. According to the test and analysis results, HCl + HNO3 compound acid was used to treat GH4169 alloy which could effectively remove the dense oxide film Cr2O3 and Al2O3 on the surface. The results revealed that interface reaction layer was not formed between the joint where only exited diffusion pore. As the joining temperature, holding time and diffusion pressure growing, the number of joint diffusion pore reduced and its size also becomed smaller.In this paper, tensile strength was adopted to evaluate the mechanical properties of GH4169 alloy diffusion bonding joints. On the condition that T = 1100℃, t = 90min, P = 40MPa, the diffusion pore in the joints disappeared during this time while the joint tensile strength was up to 707MPa and joint deformation reached 9.8%. At this time joint fracture at the interface was proved to be brittle fracture.Pure Cu foil interlayer was adopted to GH4169 alloy indirect bonding. In this case, only solid solution layer was generated in the joint interface; with the interlayer thickness reduced, the joint strength gradually improved; when the Cu foil interlayer thickness reached 20μm, with the joining temperature increased, holding time prolonged and the pressure enhanced, the solid melts layer gradually thicken and tensile strength of joints had a trend that change in rapidly growing at first and then change gently. When T = 950℃/ t = 60min / P = 10MPa, the joint tensile strength reached 720MPa; joint fractures were in the middle layer of Cu.When pure Ni foil interlayer is adopted to GH4169 alloy indirect bonding, the joint interface was similar to the joint of direct diffusion bonding where only diffusion pores presented; with the joining temperature increased, holding time prolonged and the pressure enhanced, diffusion pores gradually disappeared and the joint tensile strength exhibited a trend that rapidly growing at first and then slowly changing. When T = 990℃/ t = 75min / P = 15MPa, the joint tensile strength is up to 840MPa; joint fractures were in the middle layer of Ni foil. Finally, Pure Ni foil interlayer was adopted to GH4169 alloy indirect bonding. In order to obtain little deformation, the method of overall binding was used to bond GH4169 alloy.