Wetting of Non-Reactive and Reactive Metallic Substrates by Brazing Liquids

A survey of wetting as central phenomenon in soldering and brazing technologies are presented in this paper. The wettability is expressed by the magnitude of wetting angle. The equilibrium condition is widely investigated in the case of non-reactive partners. The phenomenon is less documented in the case of reactive partners, when chemical reaction (hence, local compositional change) also occur between the contacting phases. The brazing process belongs to this category. The mutual wettability is basic requirement for the formation of strong and durable bonding between the machine parts. Therefore, the correlation between the wetting angle (Θ) and the strength of the resulting bonding will be investigated. Not only the chemical concentration change, but phase transformations may also occure in such brazing procedure, when the contacting partners are reactive. As the chemical potencial of components are also change in this cases, the phase transformations has also impact on the evaluation of wetting angle between the brazing pool and alloy pieces to be joined. This phenomena will also be demonstrated in the case of non-reactive and reactive partners as well.