Study On Microstructure And Mechanical Property Of The Diffusion Bonding Joint Of GH4169 Foil

The diffusion bonding of GH4169 foil with nickel interlayer was studied, and the effect of grain size and the phase composition with different welding thermal cycling and heat processing were investigated. The effect of joints, elements diffusion and tensile strength with different diffusion bonding temperature, time and pressure were analyzed by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The grain size and phase compositon were studied with welding thermal cycling, solution,δphase andγ″phase aging.The clamp apparatus of welding and leaking test were designed, the diffusion bonding and property test of diaphragm capsule were carried out.The diffusion bonding joint was composed of a nickel interlayer and two deformed layers which were formed by the tension stress with cooling procedure, and the width of interlayer and deformed layer were 12-14μm, 2-8μm respectively. Elements diffusion of the joints were determined by temperature, time and pressure, the elements diffused sufficiently at 1150℃, and the relative mass of nickel element decreased from 47.6 to 8.81, concentration gradient of Ni reduced obviously..With the increase of the diffusion bonding parameters, diffusion bonding holes were prone to intimate contact, concentration gradient of diffusion elements decreased and the tensile strength of joints increased gradually. The tensile strength of joints reached to 660MPa at 1100℃for 60min under 30MPa, which was 92.2% of the tensile strength of the solution base metal. The location of rupture was in the nickel interlayer nearby the interface, fracture analysis revealed that the rupture of joints was plastic.The effect of welding thermal cycling and different heating processing on grain size and phase compositon were investigated. Superalloy recrystallized in the first cycling because of the residual stress in the base metal after forging, the grain size decreased from 33.13μm to 26.14μm. With the increase of cycling, dissolution of second-phase and inclusion weakened the pinning effect on grain boundary, the grain size reached to 48.38μm after 5 times cycling. Theδphase precipitated in the form of nonuniformly distributed on the grain boundary near the niobium inclusion, on the ordinary grain boundary, in the grains at 900℃with the aging time from 0.5h to 48h, respectively, and the size of grains increased from 55.03μm to 73.08μm. Theγ″phase precipitated in the form of dispersively distributed tiny particles in the local area, and the precipitation generated segregation in large area. The grain size reached 30.94μm, which is smaller than the base matel.Stress analysis of the diaphragm diffusion bonding was studied, and the clamp apparatus of welding and leaking test were designed. The good quality joint was acquired at 1100℃for 60min under 30MPa, and the airtight coating test of diaphragm capsule under 3MPa for 20min was carried out without leaking.