In active metal – ceramic bonding, reactions taking place between Ti and Al₂O₃ are of particular interest. The reliability of the joint depends on the metal-oxide reactivity and, consequently, on the interfacial microstructure.

The paper is presenting the results obtained in the vacuum brazing of alumina and copper parts using Ti as an interlayer between alumina and AgCu brazing alloys. Ti layer was deposited by vacuum cathodic arc method using ion bombardment with Ti ions originating from the highly ionized arc plasma, at a substrate temperature in the range of 250⁰ C to 350⁰ C. In order to control the shape of the deposited area, metallic Ti masks were used. As it is well known, the energy and intensity of the ion flux impinging on the substrate have a significant influence on the deposited film and interface structure. The higher the energy and density of the ions, the deeper the intermixing zone at the interface. The effects of the alumina substrate bombardment with medium energy Ti ions (0.5 ÷ 2.5 keV) – resulting from dc and pulsed biasing of the substrate during deposition – on some characteristics of the Al₂O₃/Ti interface were analyzed. XRD was used for phase identification at the interface. Elemental composition (AES), chemical nature and oxidation state (XPS) of the elements comprising the interface were also determined.

Different experimental conditions may affect the diffusion path in the Ti-Al-O system. In our case, the long term diffusion bonding is not applying, but it was observed that at low temperature deposition, Ti reacts with Al₂O₃ forming titanium oxides. The purpose of the present work is to investigate the interfacial reaction products in Ti/Al₂O₃ joints obtained in the context of diffusion taking place during Ti vacuum arc ion assisted deposition and during the brazing process (TiAgCu alloy formation). The characteristics of the interface were corroborated with the alumina/copper joint strength.

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