Fabrication and characterisation of silicon carbide/superalloy interfaces

Both silicon carbide ceramic (sintered SiC or reaction-bonded Si-SiC) and Inconel 600 superalloy (Ni72Cr16Fe8 in wt.%) are promising structural materials for high temperature application because of their excellent mechanical properties and good high temperature corrosion resistance. In this study, the reaction-bond silicon carbide (RBSC) was joined to an Inconel 600 (Ni72Cr16Fe8 in wt.%) superalloy using the diffusion bonding method at temperatures from 900 to 1080 °C. The interfacial reaction between the RBSC and superalloy was investigated using optical and scanning electron microscopy (SEM), coupled with energy dispersive X-ray analysis (EDX) and wavelength dispersive spectroscopy (WDS). The reaction products were also studied using X-ray diffraction technique. The mechanical properties of the joints were examined using shear testing. Experimental results showed that the interfacial reaction products at 900 and 950 °C were various silicides with some voids formed in the RBSC. As the bonding temperature increased to 1000 °C, the superalloy/RBSC reactions become more intensive, although some pores in the RBSC were filled by the reaction products. With the bonding temperature increasing to 1080 °C, a thin layer of CrSi2 was formed at superalloy/SiC interface without formation of any pores in the RBSC. The shear strength of this joint was measured as 126 MPa.