Effect of the countermaterial on the tribological behavior of Cu45Zr46Al7Nb2 bulk metallic glass

Bulk Metallic glasses (BMGs) are produced through an extremely fast cooling process of a liquid metallic alloy (with a specific composition), so that the final solid state material is deprived of crystalline structure. The resulting mechanical properties of BMGs are of great interest for number of applications, including tribological applications. Recent studies highlighted a probable dependence of the friction and wear of BMGs on the coun-terface material. The present study investigates the relationship between the tribological behavior of Cu45Z-r46Al7Nb2 BMG plates and six different countermaterials under linear reciprocating sliding. The selected countermaterials are: AISI 52100 and AISI 440C steels, brass and bronze, Cu45Zr46Al7Nb2 and Zr60Cu28Al12 BMGs. Results confirm that friction and wear are strongly correlated with the creation of a third body in the contact, whose nature (composition and morphology) depends on the countermaterial. Material transfer occurs either from the counterpart to the BMG or vice-versa, and the phenomenon is rather driven by the chemical affinities between the oxides formed than by the hardness and class of countermaterials (i.e. steels, Cu-based alloys, and BMGs). BMG/Brass contact indeed exhibits the lowest friction and the lowest wear while friction of BMG/bronze is two-fold higher and wear is among the highest of all the contact configurations tested.