Friction bonding of silicon carbide to oxygen free copper with an intermediate layer of reactive metal

Intermediate layers of various metals ranging from reactive metals to noble metals have been applied to the friction bonding of SiC (pressureless-sint ered silicon carbide) to Cu (oxygen free copper), and their influences on t he bond strength and microstructures of the joint have been systematically investigated by TEM observations. When thin foils of reactive metals Al, Ti , Zr, and Nb were applied as the intermediate layer, the bond strength of S iC to Cu was improved remarkably. In contrast, when intermediate layers of Fe, Ni, and Ag were applied, the SiC specimen separated from the Cu specime n immediately after the bonding operation without application of external l oad, similarly to the case of bonding without an intermediate layer. In the joint bonded with the intermediate layers of the reactive metals, the inte rmediate layer was mechanically mixed with Cu to form a mixed region as wid e as a few 100 mu m. TEM observations have revealed that very thin reaction layers between the ceramics and reactive metals formed. When the Ti interm ediate layer was applied, a TiC layer 10-30 nm thick formed over the almost whole interface, and between this layer and the SiC matrix a very thin lay er of a Cu solid-solution was detected. On the other side of the TiC layer, a Ti5Si3 layer similar to 100 nm thick was partially observed. When the Nb and Zr intermediate layers were applied, very thin interfacial layers wher e Nh and Zr were significantly concentrated were observed in addition to th e reaction layers of Nb5Si3, NbC and ZrC. These interfacial layers can be c haracterized by their much smaller thickness and finer grain size than thos e observed in diffusion-bonded and brazed joints, Apart from the layers men tioned above, amorphous silicon oxide layers were occasionally observed, su ggesting that the reactive metal enhanced the removal of the oxide film on the SiC surface.