Metal-ceramic interfaces: wetting and joining processes

Metallic alloys and ceramic materials are employed in aggressive and hostile environments, ranging from aerospace to energy production, from offshore to biological applications. Today, production requires materials able to survive for a long time at high temperatures, in highly aggressive atmospheres, both from the chemical and the mechanical points of view. No single material can offer these characteristics, so that 'composite' structures (composites, multilayer materials, metal-ceramic joints) are designed and tested under extreme conditions. In this paper are presented the basic principles underlying joining technologies, which can be seen also as a particular process pertaining to solidification phenomena, a short discussion of the thermodynamic background of wetting processes, recent developments related to non-reactive and reactive wetting, the influence of trace chemical elements (in the solid, liquid and gaseous phases), and some specific aspects of brazing and transient liquid phase joining processes.