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The dry-sliding tribological properties of TiAl alloy and its composite Ti2AlN/TiAl were investigated comparatively in the temperature range of 25-800 °C. The wear test results showed the wear resistance of TiAl alloy and Ti2AlN/TiAl composite from 25 to 400 °C was poor, but it improved obviously when temperature was above 600 °C. Also, 15 vol.% incorporation of Ti2AlN particles was beneficial to improve the friction and wear properties of TiAl. Protective oxide layer generated on the wear surface of 15 vol.% Ti2AlN/TiAl composite from 25 to 400 °C, hence, the wear resistance improved. Ti2AlN particles played a load-carrying role and inhabited the delamination of enamel layer effectively when the temperature was above 800 °C. Overall, Ti2AlN particles which acted as hard spots changed the state of wear surface and further provided a second phase strengthening effect, which resulted in the difference in tribological behaviors between TiAl alloy and its composite. [ABSTRACT FROM AUTHOR]

TiAl matrix composites reinforced with Ti2AlN were fabricated by in situ reactive method of powder metallurgy. Microstructures, bending properties at room temperature and compressive properties at elevated temperatures were investigated in contrast with those of TiAl alloy. The results reveal that the microstructure of TiAl matrix is significantly refined due to the synthesis of Ti2AlN. 15 vol.%Ti2AlN/TiAl exhibits excellent bending properties at room temperature, with bending strength of 753 MPa and fracture strain of 0.74%, which are 24.3 and 19.7% higher than those of TiAl alloy. The compressive strength of Ti2AlN/TiAl is markedly improved in comparison to that of TiAl alloy at elevated temperatures. Noticeably, the compressive strength of 15 and 35 vol.%Ti2AlN/TiAl increases by 67.4 and 58.7% at 1000 °C, respectively. The remarkable enhancement of mechanical performance is mainly due to the noteworthy refinement of TiAl matrix and the efficient obstruction of Ti2AlN particles to crack propagation, as well as the effective load-carrying role of Ti2AlN with high elastic modulus. [ABSTRACT FROM AUTHOR]

In current investigation, tribological properties of TiAl matrix composite reinforced with 15 vol%Ti2AlN and TiAl alloy prepared through in situ reactive method of powder metallurgy were evaluated against Si3N4 balls at room and elevated temperature. The wear mechanism along with the variation of temperature was also systematically analyzed. The results reveal that Ti2AlN/TiAl presents lower friction coefficients and wear rates in comparison with TiAl alloy at all test conditions. Along with the increment of temperature, the primary wear mechanisms of two materials both transform from abrasion wear to adhesion wear. Particularly, more efficient formation of tribo-oxidation films with protective feature on the worn surface of Ti2AlN/TiAl plays a dominant role in the improvement in wear resistance at elevated temperature. Additionally, the excellent tribological properties of the composite attribute to the other advantages of additive Ti2AlN phase, such as the load-carrying role, inhibition on the slipping of wear debris, as well as the refined microstructure of TiAl matrix phase. [ABSTRACT FROM AUTHOR]