The peculiar properties of the refractory transition metal diborides make them suitable for use in environments where high temperature, high thermal fluxes and severe surface stresses are involved. In order to improve their resistance to thermal stresses and oxidation, SiC- borides composites are often employed.
Joining these materials to themselves or to special alloys offers advanced possibilities and flexibility to designers: thus, studies on their wettability by molten filler alloys, the knowledge of the chemical and physical properties of the newly formed metal-ceramic interfaces and the optimization of the derived brazing processes are mandatory.
In this paper a study is presented on the wettability of ZrB2-SiC composites by Ag- and Cu-base alloys to be used as brazing phases to join the composite to the Ti6Al4V alloy. Thanks to its excellent fracture toughness and corrosion resistance, the latter is of special interest for aerospace and energy production components, as well as for biomedical and lightweight industrial applications.
Wettability tests aimed at elucidating the interfacial interactions and the role of “active metal” additions (e.g.Ti) in the brazing procedure are presented; they have been performed under strictly controlled physico-chemical conditions in a temperature range between 1000 °C and 1100°C.
The goal of the work is to define a brazing process through the formation of a transient liquid phase which homogenizes, as a result of chemical interactions with and diffusion into the adjoining solids, leading to reliable metal-ceramic brazed joints. The results of shear tests on the joints coupled with microstructural and microchemical description of the interfaces are presented as well.