LAYER STRUCTURE AND FRACTURE STRENGTH OF SIC CR JOINT/

Solid-state bonding of pressureless-sintered SiC has been carried out using 20 mu m Cr foil at temperatures from 1373 to 1773 It for a const ant 1.8 ks in vacuum. The formation of reaction phase and microstructu re at the interfaces between SIC and Cr were investigated by X-ray dif fraction and electron probe microanalysis. At the bonding temperature of 1373 K, the cubic Cr23C6 phase next to Cr and the hexagonal Cr7C3 p hase next to SIC were formed. Further, the cubic Cr3SiCx phase appeare d on the SiC side at bonding temperature 1473 K. Upon the rise of join t temperature to 1573 K, the hexagonal Cr5Si3Cx phase is formed at the interface of SiC/Cr3SiCx. At a highest bonding temperature of 1773 K, Cr, Cr23C6, Cr7C3 and Cr3SiCx were consumed and resulted in the forma tion of the layered structures such as SiC/Cr5Si3Cx/Cr7C3/Cr3Si3Cx/SiC . The strength of SIC joint with Cr7C3 adjacent to SIC showed the maxi mum strength, and degrades with the formation of the brittle phases of Cr3SiCx and Cr5Si3Cx.