Evolution and formation mechanism of the interfacial microstructure on diffusion bonded joints of single crystal Ni-based superalloys to Ti₃AlC₂ ceramic with Ni interlayer

Single crystal Ni-based superalloys DD3 and nanolaminated ternary ceramics Ti₃AlC₂ were the critical high-temperature structural materials, so the bonding of them is of great significance in promoting their potential applications at elevated temperatures. A strong DD3/Ti₃AlC₂ joint with the average shear strength of 86.4 MPa was obtained by vacuum diffusion bonding using the Ni interlayer at 900 °C for 60 min. The joint microstructure and its formation mechanism were investigated in detail. Especially, the role of Ni diffusion in the process of forming a mixed phase zone at the Ti₃AlC₂ interface was clarified. The diffusion zone adjacent to the DD3 was mainly composed of (Ni)_ss, where Al and Ti existed mainly in the form of solid solution. In contrast, a more complex diffusion process occurred at the Ti₃AlC₂ interface. A Ni₃Al single layer and a mixed phases zone, containing Ni₃Al, AlNi₂Ti and TiC, were formed from the Ni interlayer to the Ti₃AlC₂ substrate. Ni had a strong tendency to diffuse along grain boundaries of the Ti₃AlC₂ substrate, leading to the decomposition of its nanolaminated structure. Along with inward-diffusion of Ni, the Ni₃Al phase was mainly formed, and a small amount of AlNi₂Ti and TiC were also formed.