Analysis of the interface and strength of diffusion bonding for GH4169 sheets assisted by a nanoscale nickel interlayer

The development of a new generation of high thrust-to-weight ratio aeroengines strongly relies on the adoption of thin-walled hollow components made of nickel superalloys for high-end aerospace equipment to achieve structural lightweighting, making high-quality diffusion bonding technology an urgent need. This study aims to address the key issues faced in the diffusion bonding of GH4169 alloys, such as a low interfacial bonding rate, insufficient bonding strength, and easy structural deformation. It proposes the introduction of a nanoscale nickel interlayer to assist in the interfacial diffusion and microstructural evolution of GH4169 alloys. The microstructures, elemental distributions and mechanical properties of the joints at different temperatures are systematically characterized and analyzed by methods such as scanning electron microscopy (SEM), transmission electron microscope (TEM), electron backscatter diffraction (EBSD) and shear testing. The results show that the interlayer of nanoscale nickel, with high-density grain boundaries, serves as a rapid diffusion channel and a source of high-energy driving force, significantly promoting the mutual diffusion of elements and the relaxation of interfacial strain energy and thereby effectively inhibiting the formation of Kirkendall pores and the precipitation of brittle phases such as δ-Ni₃Nb. Under 1050 °C/15 MPa/90 min, the average shear strength of the joint reaches 235.7 MPa. This study reveals that the nanoscale intermediate nickel layer, through the synergistic mechanism of "accelerated diffusion–strain release–brittle phase suppression", thereby establishing a synergistic mechanism for interfacial healing, providing a feasible approach for achieving low-deformation and high-quality bondings in complex GH4169 alloy components for aerospace applications at comparatively lower temperatures.