A Study of Frictional Adhesion between Dissimilar Metals with a Background of Development of Cold Pressure Welding Using Interfacial Slide

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Characteristics of adhesion between dissimilar metals under sliding friction were investigated to serve for cold pressure welding using interfacial slide. Pin-on-plate type sliding friction test was at first applied according to the research project. Aluminum showed strong adhesion, but a problem arose that iron, nickel and titanium chosen as the materials did not show adhesion at all. The problem and an additional difficulty that no information was presented on the effect of sliding length, one of important factors in actual joining processes, let us to stop using the friction test. Then a disc-on-disc type sliding adhesion test was employed in place of the pin-on-plate type test. In the sliding adhesion test, a pair of test- pieces joined each other at the interface by adhesion, and the strength of joining was measured as adhesive strength in order to estimate the degree of adhesiveness quantitatively from practical view point. Influences of the pressure and sliding length were examined, and after that adhesiveness in the various combinations including similar metal ones were evaluated. And the following suggestive information was obtained:1. Adhesive strength strongly depends on sliding length and shows a maximum at a certain sliding length. And the maximum shifts to shorter sliding length with an increase of the pressure. 2. An annealed material shows higher adhesive strength than work-hardened one in the same pressure. But taking flow stress into consideration, both are unified on behavior. 3. Adhesive strength shows a correlation with the threshold of reduction in height to start joining in cold pressure welding by upsetting. 4. Adhesive strength well expresses the degree of adhesiveness, and it can be used as the index to judge whether a particular metal combination is suited to apply cold joining process using interfacial slide.