Tribological Performance and Tribofilm Evolution of TiAl Matrix Composites with Silver and Titanium Diboride at Elevated Temperatures

Abstract

In order to understand the anti-friction and anti-wear mechanisms of silver (Ag) and titanium diboride (TiB2) at elevated temperatures, the tribological performance and tribofilm evolution of TiAl matrix composites with Ag and TiB2 (TATs) are studied from 200 to 800 °C. The results illustrate that TATs exhibit excellent friction-reducing and anti-wear properties, which are attributed to the self-adjusted synergistic effect of Ag and TiB2 in the wide temperature range. Besides, the testing temperatures have strong influence on the chemical structure and evolution of tribofilms. Within 400 °C, Ag migrates to worn surface and mixes with TiB2 to form the Ag-rich tribofilms. At 600 °C, the lubricating effect of Ag diminishes and the oxidation of TiB2 is limitation, hence there is no well-consolidated tribofilm on the worn surface. At 800 °C, Ag loses the lubricating capacity, while TiB2 completely oxidizes to form B2O3, resulting in the formation of B2O3-rich tribofilms.