Joining SiC ceramic and metal Mo with AuPdCoMnNi alloy and interfacial reactions

For high-temperature joining of SiC ceramics, a multi-element AuPdCoMnNi alloy was designed and used as filler metal to join SiC ceramics to metal Mo. The brazing experiment was conducted under the condition of 1150 °C for 5 min and 10 min, respectively. The results show that numerous micro-cracks are visible in the directly brazed Mo/SiC joints, which are continuously distributed in bands of (Co, Ni)-Si and (Pd, Ni)2Si compounds. SiC was further joined to Mo using a Kovar interlayer under the same brazing conditions, and the metallurgical quality of the joints was evidently improved compared with the joints without this interlayer. The joining layer was mainly composed of (Au, Mn)ss layer mixed with element C, (Fe, Co, Ni, Mo)-Si compound layer and (Fe, Co, Ni)-Si compound with discontinuous (Pd, Ni)2Si phases and some small fragments of (Fe, Co, Ni, Mo)-Si compounds. In addition, the shear strength of the joints with Kovar interlayer reaches 55.36 MPa, remarkably higher than the void. The joining mechanism was also discussed.