Effect of diffusion time on interfacial microstructure of TLP joints of DD6 single crystal superalloy

Transient liquid phase diffusion bonding of DD6 single crystal superalloy was achieved using 30μm thick BNi2 filler foil as interlayer at 1100℃/20 min. The effect of diffusion time at 1180℃ on the interfacial microstructure was investigated. The distributions of alloy elements in joint region were analyzed in detail. The results showed that the needle-like boride gradually dissolved and disappeared in the joint region with the extension of diffusion time. After a long time diffusion, γ' phase in DD6 substrate grown and connected to each other, formed net structure. After 16 hours of diffusion, the elements Al and Si in joint and DD6 substrate were homogenized. However, because the diffusion speeds of elements Cr and Co were relatively small, the uniformity degree of Cr and Co in joint and DD6 substrate was obvious. In addition, due to the lowest diffusion speed of elements W and Re, it was difficult to realize their homogenization in joint and DD6 substrate.