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

摘要

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 degrees 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.