Study On Preparation And Tribological Properties Of Multi-component TiAl Matrix Self-lubricating Composites

As liquid lubricant failed to work effectively at high temperature and coating have limited service life, solid self-lubricating composite which had excellent tribological properties under extreme environment conditions and a longer lifespan due to the self-repair capability was a hot research field of tribology.It was hard for single lubricant to realize the lubrication over a wide temperature range, and the study of synergetic effect of more than two lubricants became attractive. By adding Ag, Ti3SiC2 and BaF2/CaF2 eutectic(ATBC) into TiAl matrix, a new type TiAl matrix self-lubricating composite was fabricated successfully. Dry sliding tribological behaviors of TiAl matrix self-lubricating composites containing ATBC from room temperature(RT) to 600°C were experimentally studied. The results implied that the TiAl matrix self-lubricating composite had excellent tribological properties over an extreme range of operating temperatures, which was attributed to the synergetic effect of Ag, Ti3SiC2 and BaF2/CaF2 lubricants.In pervious study, the self-lubricating composite was usually prepared by adding solid lubricant in the matrix. The frictional property was less affected if the adding amount of lubricant was too low, while if adding a large amount of lubricant, the mechanical properties would decrease significantly. The addition of effective reinforcement phase could be an approach to enhance the microstructure of the composite and improve the anti-wear ability. TiB2 was chosen to improve the mechanical properties of TiAl-12 Ag self-lubricating composite. Dry sliding tribological behaviors of TiAl matrix self-lubricating composites containing Ag and TiB2 from RT to 600°C were experimentally studied. The results indicated that the addition of TiB2 obviously enhanced the wear resistance of the composite.The tribological properties of TiAl-12Ag-5TiB2 under different working conditions, including the load, sliding velocity and counterface materials, were researched. The tribological properties were strongly dependent on the working conditions. The friction coefficients decreased with the increase in load, while the wear rates increased with the increase in load; the friction coefficients and wear rates decreased with the increase in sliding velocity; Ti Al-12Ag-5TiB2 showed the best tribological properties when sliding against Si3N4, compared with Al2O3 and WC-6Co.Moreover, the excellent tribological properties of self-lubricating composite were primarily attributed to the formation of expected frictional layer on the worn surface. This article was dedicated to explore the possible formation and acting mechanism of frictional layer of TiAl-12Ag-5TiB2 composite. At normal load of 12 N, a frictional layer that consisted of lubricating film, mechanically mixed layer and plastic deformation layer was observed. The plastic deformation layer improved the deformation resistance of composite and had high bonding strength with other layers. The mechanically mixed layer that consists of lubricants could be continuously provided to the worn surface to form a tribofilm with low shearing stress junctions, lowering the friction coefficient and wear rate.