Tribological Properties of TiO₂/BP Nanocomposites as Lubricant Additives for Titanium Alloy Tribopairs

To improve the tribological performance of titanium alloy, the novel nanocomposites titanium dioxide/black phosphorus nanosheets were successfully prepared by a sol-gel method. The effects of the concentration of the black phosphorus nanocomposites, the ratio of TiO₂ to black phosphorus, and the load and sliding velocity on the friction and wear of the titanium alloy friction pair under boundary lubrication conditions were investigated using a ball-on-disc tribometer with an orthogonal experimental design. Based on the results of the analysis of variance, the degree of influence of each factor on the friction and wear was obtained. The results show that these factors have different effects on the tribological behavior of Si₃N₄-Ti6Al4V(TC4) tribopairs. Load has the greatest influence on the friction and wear of the titanium alloy. When the antiwear performance of the upper Si₃N₄ ball was chosen as the response index, the optimum tribological conditions were obtained: load, 5 N; sliding velocity, 33 mm/s; mass ratio of TiO₂ to black phosphorus nanosheets, 2:1; and additive concentration, 0.01%. The excellent tribological performance could be ascribed to the formation of a tribolayer containing nanocomposites, which played the role of buffering and isolating the Si₃N₄-TC4 tribopairs.