Joining SiC ceramic to Ni-based superalloy with Zr/Nb multiple interlayers

Joining SiC ceramic to Ni-based superalloy (type GH128) has been realized by diffusion welding with Zr/Nb multiple interlayers. The effects of welding temperature, duration to keep the temperature and welding pressure on the bending strength of welded samples were studied. The optimized technical parameters are obtained as follows: the temperature, the dwelling time and the pressure are 1070°C, 20 min and 11.5 MPa respectively. Under these conditions, the bending strength of the welded sample is 52% of the bending strength of the SiC ceramic. In bending test, the cracking of the welded sample occurs partially at the SiC/Zr interface and partially in the ceramic near welding seam. These experimental results indicate that Zr/Nb multiple interlayers significantly relax the welding thermal stress generated due to the thermal mismatch of the dissimilar materials to be welded. The mechanism of bonding was investigated based on the observation of the microstructure and the determination of the distribution of the elements at the welded area, which show that interdiffusions take place at the interfaces and contribute to bonding at the interface. In addition, mechanical bonding forms at the Zr/SiC interface due to the penetration of Zr into the open pores of the SiC ceramic.