Effects of normal load and reciprocating frequency on the tribological behaviors of a Zr-based bulk metallic glass

Abstract

Bulk metallic glasses (BMGs) are a class of novel engineering materials of high hardness, high strength, and excellent fracture toughness which imply prospective outstanding wear resistance. However, for the non-intrinsic character of tribological properties, the wear behaviors and mechanisms of BMGs remain to be clarified. In this work, linear reciprocating tribological behaviors of a Zr60.14Cu22.31Al9.7Fe4.8Ag3 (at.%) BMG against GCr15 steel balls were characterized in the “ball-on-plate” mode under normal loads of 1–15 N and at reciprocating frequencies of 1–12 Hz with a stroke length of 5 mm. The results indicate that high coefficient of friction (COF) was observed under low normal load plus high reciprocating frequency, whereas low COF was observed under high normal loads or at low reciprocating frequencies, and that the specific wear rate increased with both normal load and reciprocating frequency wherein the reciprocating frequency played a more crucial role. Via systematic examinations on the worn surfaces of both BMG plates and GCr15 steel balls and on the wear debris, transition of the dominating wear mechanisms from oxidative wear and abrasive wear to adhesive wear with increasing normal load and reciprocating frequency was detected and the role played by plastic deformation of BMG in the process was tentatively illustrated. The current work would help to understand the tribological properties of Zr-based BMGs under sliding conditions.