Friction and wear of Pd-rich amorphous alloy (Pd₄₃Cu₂₇Ni₁₀P₂₀) under dry and ionic liquid (IL) lubricated conditions

Palladium (Pd) based metallic glass has attracted attention because of its superior tribological performance thereby becoming a potential material to solve contact induced failures and improve the reliability of many engineering applications. In this study, Pd-rich metallic glass (Pd₄₃Cu₂₇Ni₁₀P₂₀) was synthesized, and novel experiments were designed to obtain fundamental insight into its friction and wear behavior. The tribological performance of amorphous (i.e., Pd-rich amorphous alloy) and crystalline (i.e., pure crystalline Pd) palladium under dry and lubricated contact condition was investigated through the reciprocating ball-on-disc tests. The ionic liquid (IL), i.e., 1-nonyl-3-methylimidazolium bis[(trifluoromethane)sulfonyl]amide ([C₉C₁im][NTf₂]), was applied as a lubricant. Under the controlled contact conditions (i.e., sliding velocity, contact load, and environment temperature), the in-situ friction and ex-situ wear were measured and compared quantitatively. First, at dry contact conditions, the amorphous Pd alloy showed much lower coefficient of friction and wear than the crystalline Pd. Three wear mechanisms (delamination, abrasive and adhesive wear) were identified on the crystalline Pd, whereas the amorphous Pd alloy showed single dominant wear mechanism, namely abrasion. Next, when the IL lubricant was applied to the contact interface, it significantly improved the friction and wear of both amorphous and crystalline Pd samples. Only abrasive wear mechanism was observed on both types of Pd samples. In particular, the IL lubrication was more effective to the crystalline Pd sample partly because of the tribofilm formation on the surface.