Reaction-composite diffusion brazing of C-SiC composite and Ni-based superalloy using mixed (Cu-Ti) plus C powder as an interlayer

Taking the advantages of reaction-composite brazing and transient liquid phase bonding (TLP), a novel process with the features of low-temperature bonding & high-temperature resisting was implemented to join C-SiC composite and GH4169 superalloy. In the new process, mixed powder of low-melting-point Cu85Ti15 alloy and carbon (C) was used as an interlayer. At a relatively low bonding temperature (990 degrees C), in-situ reaction of (Cu-Ti) (l)+C-s ->(Cu)(s)+TiCs and interdiffusion between the (Cu-Ti)(l) liquid and the GH4169 substrate concurrently occurred to transform the interlayer into a TiC-reinforced (Cu)(s) matrix composite joining layer. The low-CTE reinforcement TiC helped to alleviate the high residual stress in the joint, and the (Cu)(s) matrix provided the high-temperature resistance for the joint. In the current work, microstructural behavior, formation mechanism, heat resistance and shear strengths of the bonded joints were investigated. Results indicated that the (Cu-Ti)(l)/C-s in-situ reaction had an effect of shortening the solidification time of the joining layer, thus decreasing the formation of Ti-C and Ti-Si brittle compounds at the C-SiC side interface. The bonded joints exhibited excellent comprehensive properties: melting temperature of the joining layer reached 1052 degrees C, which was much higher than that of Cu85Ti15 alloy (898 degrees C) and the bonding temperature (990 degrees C); the maximum shear strength at room temperature and 900 degrees C reached 234 MPa and 101 MPa, respectively.