Self-lubricating behavior of a PdCuNiP glassy alloy by in-situ nanocrystallization during dry friction

Abstract

In the present work, dry-sliding behavior of a PdCuNiP bulk glassy alloy (BGA) was studied and compared with that of a ZrAlNiCu BGA. The PdCuNiP BGA exhibits a 2-fold smaller coefficient of friction (COF) and a 100-fold lower wear rate than those of the ZrAlNiCu BGA, although the PdCuNiP BGA shows the smaller hardness and fracture toughness. The unprecedented low COF and wear rate of the PdCuNiP BGA stem from in-situ formation of an amorphous/ultrafine nanocrystalline structure layer on the wear-scar surface during the dry sliding. The Von-Mises stress simulation mapping in the contact area reveals that the effect of stress and deformation is not the primary cause for the nanocrystallization. The model calculated frictional heat generated during the friction process causes the in-situ nanocrystallization, which increases the hardness and strength of surface layer. The self-lubrication effect results from the effective suppression of the sliding-induced plastic deformation and surface roughening.