Tribological Behavior and Self-Healing Properties of Ni[sub.3]Al Matrix Self-Lubricating Composites Containing Sn-Ag-Cu and Ti[sub.3]SiC[sub.2] from 20 to 800 °C

As a high-temperature structural material, Ni[sub.3]Al matrix composites are often used to manufacture basic mechanical components that need to be used in high-temperature conditions. To meet the increasing demand for metal matrix composites with an excellent tribological performance over a wide temperature range, Ni[sub.3]Al matrix self-lubricating composites containing Sn-Ag-Cu and Ti[sub.3]SiC[sub.2] (NST) were synthesized via laser-melting deposition. Dry sliding friction tests of NST against Si[sub.3]N[sub.4] ball were undertaken from 20 to 800 °C to investigate the tribological behavior and wear-triggered self-healing properties. The results show that the tribological behaviors of NST are strongly dependent on the testing temperature and self-healing properties. At low and moderate temperatures from 20 to 400 °C, as the Sn-Ag-Cu flows into the cracks and is oxidized during sliding friction, while the cracks on the worn surface are filled with oxides consisting mainly of Al[sub.2]O[sub.3], SnO[sub.2] and CuO. At higher temperatures of 600 and 800 °C, the cracks are filled by the principal oxides of Al[sub.2]O[sub.3], TiO[sub.2] and SiO[sub.2] due to the partial decomposition and oxidation of Ti[sub.3]SiC[sub.2]. Compared with other testing temperatures, the recovery ratio relative to the Ni[sub.3]Al base alloy of the cracks on the worn surface of NST is the highest at 400 °C, which is about 76.4%. The synergistic action mechanisms of Sn-Ag-Cu and Ti[sub.3]SiC[sub.2] on the crack self-healing from 20 to 800 °C play a significant role in forming a stable solid lubricating film, improving the anti-friction and wear resistance of NST. The results provide a solution allowing for metal matrix composites to achieve excellent lubrication stability over a wide temperature range by virtue of the crack self-healing properties.