Ni3Al-based superalloy is an important material for key parts of aero-engine blades, turbine disks, combustion chambers, etc. The hot end component is designed with a hollow structure with a complicated internal cooling channel, and it is difficult to achieve its final structure through a casting process, so welding is an indispensable manufacturing technology. Transient liquid phase diffusion welding (TLP) combines the advantages of brazing and diffusion welding, and is a better way to connect Ni3Al-based superalloys.
Recently, based on the foundation of Sino-Uzbek international scientific and technological cooperation, researchers from China Brazing Diffusion Welding R&D Center have adopted new low-temperature alloys to address China’s Ni3Al-based superalloy joint gap sensitivity, low joint remelting temperature, and unstable joint quality under production conditions. The boron complex Ni3Al-based intermediate layer material system solves the problem of insufficient joint reliability when the gap is large.
By using density functional theory, the elastic constants of single crystal Ni3Al, the elastic modulus, shear modulus and Poisson's ratio of polycrystalline Ni3Al were calculated and compared with the experimental data reported by previous researchers. Based on the calculation of the mechanical properties of single crystal and polycrystalline Ni3Al, the mechanical behavior of Ni3Al single crystal instantaneous liquid phase diffusion welding joints under simple tensile load was studied by using the three-dimensional finite element method. The results show that the maximum value of the first principal stress, maximum shear stress, equivalent stress, and damage equivalent stress decreases linearly with the decrease of the elastic modulus of the intermediate layer. Reducing the elastic modulus of the intermediate layer can reduce the transient liquid phase. The stress concentration of the diffusion welding joint improves the mechanical reliability of the joint. Related scientific research results were published in the international academic journal Materials 2019, 12(17), 2765.
A new low-boron complex Ni3Al-based intermediate layer material is used for TLP connection of directionally solidified high-temperature alloy IC10. SEM and EBSD were used to analyze the microstructure of TLP connection joints, and the influence of base metal dissolution, isothermal solidification and post-weld heat treatment on the migration of main elements of the base metal was studied, and a new type of superalloy intermediate layer composition design method was proposed. Previous research is only applicable to bottlenecks with a gap of less than 0.03 mm. Under the condition of a joint gap of 0.08 mm, the tensile strength of the joint at high temperature (1100 ℃) reaches 268 MPa; the joint high temperature durability (1100 ℃/36 MPa) lasts for more than 100 h, both reach more than 90% of the base metal. Related scientific research results were published in the international academic journal Journal of Manufacturing Processes 54 (2020) 109–119.