| Joining of 304 stainless steel to Si₃N₄ ceramic using Cu-Ag-Ti-Al braze alloy was made in vacuum furnace. For the joint showing shear strength value of more than 202 ㎫, reaction products formed at the interface between Si₃N₄ and brazing alloy were investigated by O. M., SEM, EDS, WDS, XRD and X-AEM. The redox reaction of Si₃N₄ with Ti results in the formation of particulate TiN and continuous Ti_5Si₄ layers at the nearest interface. For a Cu-Ag-Ti alloy the FeTiSi on those layers was uniformly formed by solid-state reaction of Ti_5Si₄ with Fe segregated/diffused from stainless steel. But for a Cu-Ag-Ti-Al alloy the M_(1.5)Ti(M : Fe, Cr, Fe/Cr=6.4) compounds were locally formed on the Ti_5Si₄ layer and in the brazement. Titanium irregularly erodes the Si₃N₄ surface, resulting in the formation of local intrusions of TiN particles into the substrate. EDAX analyses showed that Fe and Cr diffused through the glassy phase of Si₃N₄ in the neighborhood of interface. |
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