Tribo-electrification mechanism for self-mated metals in dry severe wear process: Part II: pure soft metals

The tribo-electrification and the wear behavior are investigated for self-mated pure soft metal pairs of Pb, Zn, Al, Ag, Au and Cu in dry severe wear process. Results show that the wear type for the soft metal pairs is the flake-like wear particles due to the particle aggregation with junction growth. The polarity of electrification voltage keeps negative due to the wear loss of the pin specimen always less than the plate specimen. The flake-like particles can be considered as the bridge in the circuit system so that the generated voltage from the friction has been neutralized across this bridge. This is the reason why the electrification voltage for the soft metal pairs is smaller than that for the hard metal pairs. Another model for the tribo-electrification mechanism suitable for soft metal pairs is proposed. By combining the present results and hard metal pairs obtained from part I, the voltage of tribo-electrification is proportional to the electric resistivity with the hardness/surface energy except Ti.