Effect of natural attapulgite mineral on microstructure, mechanical properties and tribological behaviors of in-situ TiB/Ti composite by SPS method

Abstract

In this study, natural attapulgite (ATP) mineral powder was implanted into an in-situ synthesized TiB/Ti composite by the SPS method using Ti-Al-B-attapulgite raw powders to improve the tribological properties. The introduction of ATP improved the microstructure, mechanical properties, and tribological performance of the in-situ TiB-reinforced titanium matrix composite. The addition of 1 wt.% ATP powder has refined both the grain structure of the matrix and the size of the in-situ TiB, leading to the increase of 39.3% in matrix nanohardness and 31.4% in microhardness of the composite. During the friction process, dehydration reactions, group recombination, and tribochemical reactions occurred in the ATP minerals dispersed in the rubbing contact area of the composite, inducing the formation of a tribolayer with a smooth nanocrystalline film. The tribolayer is mainly composed of titanium oxides (TiO, TiO2, and Ti2O3), iron oxides (FeO, Fe2O3, and Fe3O4), ternary compounds (Al18B4O33 and Al2Ti7O15), oxide ceramics (Al2O3 and SiO2), solid lubricating phases (graphite and attapulgite), iron, and enstatite (MgSiO3). The nanocrystalline structure composed of FeO, Fe2O3, and TiO, as well as the strengthening effect of hard phases such as SiO2, MgSiO3, Al2O3, Al18B4O33, and Al2Ti7O15, endowed the tribolayer with a high hardness, good plasticity, and toughness. The exceptional mechanical properties and dispersed solid lubrication phases of the tribolayer resulted in the excellent tribological properties of the ATP-TiB/Ti composite.