Which Properties Must a Surface have to be Suitable for Cold Pressure Welding?

摘要

Cold pressure welding is a very promising welding technology, as different materials can be joined without thermally induced formation of brittle intermetallic phases in the bond zone. During an extrusion process local contact conditions allow for the formation of a strong metallurgical joint. Special surface preparations can enhance this formation of metallic bonds to result in high overall component strengths. So far, for the material combination of steel and aluminum cleaning of the surfaces by scratch brushing has been found to be beneficial for the bond formation. In this paper, the relevant surface conditions such as the amount of surface contamination and oxide layer thickness are analyzed by means of X-ray photoelectron spectroscopy (XPS). Since plasma treatments are known to influence these parameters, joining of polished samples (reference) and samples after an argon plasma treatment (physical removal of contamination) as well as oxygen plasma treatment (chemical removal) is investigated. The resulting joined samples are micro tensile tested to measure the local bond strength. It was found that the surface contamination was significantly reduced by the plasma treatment and the bond strength increased. Due to the fact that the surface tension is influenced as well, the resulting tensions were further analyzed to take the effect of the adhesion energies into account by the Owens, Wendt, Rabel und Kaelble (OWKR) method.