INTERFACE STRUCTURE AND FORMATION MECHANISM OF DIFFUSION-BONDED JOINTS OF SIC CERAMIC TO TiAl-BASED ALLOY

摘要

Diffusion bonding of SiC ceramic to TiAl-based alloy was carried out at 1473-1573 K for 15-240 mm under a pressure of 35 MPa. The kinds of the reaction products and the interface structures of the joints were investigated by SEM, EPMA and XRD. Based on this, a formation mechanism of the interface structure was elucidated.Two kinds of reaction products or new phases have formed during the diffusion bonding of SiC to TAD, namely face-centered cubic TiC and hexagonal Ti_5Si_3Cx. The interface structure of diffusion-bonded SiC/TAD joints is SiC/TiC/(Ti_5Si_3Cx +TiC)/TAD, and this structure will not change with bonding time once it forms.The interface structure of SiC/TAD joints forms according to the three-stage mechanism, namely the occurrence of a single-phase TiC layer; the occurrence of a duplex-phase (Ti_5Si_3Cx +TiC) layer; and the growth of the TiC and (Ti_5Si_3Cx +TiC) layers. In addition, the thickness of each reaction layer Increases with bonding time according to a parabolic law.