Survey on wetting of SiC by molten metals

Good wetting and low reactivity of metal/ceramic couples are key factors in many technological processes, in particular in metal/ceramic joining, to avoid degradation of ceramics and to achieve the desired properties during service. Silicon carbide is a covalent material of great technological interest due to its excellent overall properties. Starting from a survey of the surface energies of SiC and liquid metals, the reactivity and wettability of pure metal/SiC systems, as well as the wetting behavior and mechanisms of (liquid metal + Si)/SiC systems are reviewed for understanding the interfacial bonding and for supporting the development of application-oriented processes like non-reactive brazing. Silicon chemisorption and interactions between the molten alloys and SiC at the metal/substrate interface and the intrinsic properties of the alloys or of the pure metals are considered to play the key roles in interfacial bonding. In particular, additions of Si can limit or even suppress the substrate dissolution leaving the solid–liquid interface nearly undisturbed. At the same time, oxidation–deoxidation processes at the SiC surface are the basic mechanisms to be controlled in order to allow the liquid phases to contact a “pure” SiC surface. The need of further investigations, covering basic interfacial phenomena including both experiments and ab-initio modeling of the solid–liquid interfaces is strongly underlined.