Dry and lubricated tribological behavior of a Ni- and Cu-free Zr-based bulk metallic glass

• Dry and lubricated tribological behavior of ZrAlCoAg BMG was investigated.
• BMG exhibits superior wear resistance in air and PBS than Ti6Al4V alloy.
• Sliding in PBS ruins pitting resistance of the BMG and accelerates its wear damage.
• Wear deterioration in PBS is jointly controlled by abrasive and corrosive wear.

In this study, tribological behavior of a Zr53Al16Co23.25Ag7.75 bulk metallic glass (BMG) in air and phosphate buffer saline (PBS) solution was investigated and compared with biomedical alloy Ti–6Al–4V. It is found that wear resistance of the Zr–Al–Co–Ag BMG sliding in air is superior to that of Ti–6Al–4V alloy. Under dry friction condition, wear deterioration of Zr-based BMG is controlled by oxidation and adhesive wear whereas Ti–6Al–4V alloy is jointly dominated by abrasive and adhesive wear. However, Zr-based BMG presents decreased wear resistance under lubricated friction condition in comparison with dry friction condition. In contrast, Ti–6Al–4V alloy shows improved wear resistance sliding in PBS. This is probably associated with the inferior pitting corrosion resistance of Zr–Al–Co–Ag BMG in the medium containing chloride ions, which may cause tribocorrosion controlled by synergistic effects of abrasive and corrosive wear. The possible mechanism for corrosion accelerating wear is discussed based on the tribological behavior of this Zr-based BMG.