Metal Transfer during Static Loading and Impacting

Abstract

Experiments are described which investigate the metal transfer which takes place when a radioactive hemispherically ended slider is pressed normally into a flat surface of the same or another metal. It is found that metal transfer in the form of a number of small fragments is always observed, and this supports the view that metallic junctions are formed between metal surfaces in contact. Experiments in which the load is varied suggest that at the higher loads the oxide layer on the metal surfaces is broken up to a larger extent than at lower loads, and a more than proportional increase in metallic interaction and transfer takes place. An analogous effect is observed in the presence of boundary lubricants. When the surfaces are impacted together, very similar results are obtained. Somewhat less pick-up is observed than for static loading, and the difference is probably due to the fact that it takes time for strong junctions to be formed Impact experiments with surfaces covered by lubricants show that a lubricant layer may be trapped between the surfaces, and this produces a large reduction in pick-up without greatly reducing the amount of plastic deformation