Rapidly achieving high-performance joining of single crystal superalloy and powder metallurgy superalloy via partial transient liquid phase diffusion bonding

Abstract

A rapid and high-performance partial transient liquid phase diffusion bonding process has been proposed for the DD5 single crystal superalloy and the FGH96 P/M superalloy via a mixture of NiTi alloy and FGH96 P/M superalloy powders as interlayer. During the bonding process, isothermal solidification and homogenization of the joint were achieved through a rapid diffusion mechanism of short-range and large-area between the liquid phase of NiTi and the FGH96 particles and the base material. When bonded at 1170 °C only for 60 min of the holding time, isothermal solidification and homogenization of the joints were completed. The isothermal solidification joint consisted of a polycrystalline zone with γ/γ′ structure similar to that of FGH96 and an epitaxial growth zone (EGZ) derived from DD5. Compared with traditional brazing and transient liquid diffusion bonding process (TLP), no brittle compounds and eutectics of Si and B were presented in the joint, which ensured the joint with excellent mechanical properties. With the increase of holding time, both the tensile strength and elongation was significantly increased on account of the reduction of η-Ni3Ti. When the joints were bonded at 1170 °C for 60 min, the elevated temperature strength of 650 °C reached 880.7 MPa, which was more than 80 % and 60 %o that of the DD5 and FGH96, respectively.