Uma cerâmica avançada é geralmente unida ao metal pelo processo de brasagem, porém o custo das ligas de adição ativas pode ser considerado uma limitação. A brasagem com uma liga de adição isenta de metal ativo para união dos componentes é uma tentativa de transpor esta desvantagem. A difusão de um metal ativo a partir do componente de titânio através do liga de adição fundida para o componente cerâmico produziu uma liga ativa in loco, promovendo a redução do óxido de zircônio e melhorando o molhamento na superfície cerâmica. Titânio não ligado foi unido a zircônia tetragonal (Y-TZP) e zircônia parcialmente estabilizada com magnésia (Mg-PSZ) em forno de alto vácuo (<3x10-5 mbar), usando ligas comerciais Ag-28Cu e Au-18Ni. Testes de detecção de vazamento de gás hélio foram realizados na interface cerâmica/metal à temperatura ambiente; amostras de juntas estanques foram analisadas por técnicas de análise microestrutural e análise por dispersão de raios-X na seção de união das juntas. Juntas estanques foram produzidas com a liga eutética Ag-Cu, formando-se uma camada intermetálica e uma camada escura de reação próxima à superfície cerâmica; a difusão de titânio foi eficiente para promover interações químicas entre os componentes. As juntas brasadas também foram ensaiadas com teste de flexão três-pontos.

Advanced ceramic is usually joined to metal by the well-known direct brazing process, where costly active filler alloys can be considered a limitation. Brazing using active-metal-free filler alloy as insert between the joint components is an attempt to overcome it. The active metal diffusion from the titanium member through the bulk of molten filler to the ceramic was responsible to produce an active filler alloy in loco and promote reduction of the zirconium oxide to improve wetting on the ceramic surface. Unalloyed titanium was joined in a high-vacuum furnace (<3x10-5 mbar) to yttria-tetragonal zirconia polycristals (Y-TZP) and zirconia partially stabilized with magnesia (Mg-PSZ), where commercial fillers Ag-28Cu and Au-18Ni with respective thermal cycles were evaluated. Helium gas leak detection test was performed at the ceramic/metal interface at room temperature; samples from reliable vacuum tight joints were examined by microstructural analysis techniques and energy dispersive X-ray analysis at the joint cross-section. Tight joints were produced with eutectic Ag-Cu filler, revealing an intermetallic layer and a dark reaction layer near the ceramic surface; titanium diffusion was efficient for superficial chemical interactions between individual components. Brazing joints were also tested using three-point flexure testing.

The mechanical metallization is a successful technique at laboratory scale and specially applied to oxide ceramics. Indirect brazing process of zirconia to metals is achieved using active-metal-free filler alloys on previously metallized ceramic. Stabilized zirconia ceramics were mechanically metallized with Ti and wetting conditions evaluated using commercial Ag-Cu and Au-Ni fillers with its respective thermal cycles. Better results were selected for brazing ceramic to metals in a high-vacuum furnace. Reliable vacuum tight ceramic/metal joints were obtained specially using the Ag-28Cu filler for results below 10-8 mbar.ℓ.s-1; samples at the joint cross-section were examined by microstructural analysis techniques and energy dispersive X-ray analysis. Microhardness profiles were made across the joints interface where zirconia undergone a typical darkening effect during brazing. Microstructure at the braze region revealed a dark reaction layer and precipitation zone closely to metallized ceramic surface for zirconia/Ti-6Al4V joints due to chemical interactions between the individual components.