High temperature tribological behavior of a Ti-46Al-2Cr-2Nb intermetallics

Tribological behavior of a Ti-46Al-2Cr-2Nb alloy, produced by hot-pressed sintering, was investigated using a home-built ball-on-disc tribotester against a Si ₃N ₄ ceramic ball at a constant speed of 0.188 m s ^-1 and an applied load of 10 N from 20 to 900 °C. It was found that the friction coefficient decreased slowly with increasing temperature from 20 to 600 °C, and then rose and reached the highest value at 800 °C, but slightly dropped at 900 °C. The wear rate of the alloy, in the magnitude of 10 ^-4 mm ³/Nm, increased mildly with increasing temperature to a maximum value at 400 °C and then dropped rapidly from 600 to 800 °C, and increased a little at 900 °C. The wear mechanism of the alloy transformed from mainly ploughing and small delamination wear at 20-700 °C to plastic deformation and adhesive wear at 800 and 900 °C. The transition of the wear mechanism occurred between 700 and 750 °C. The friction and wear behavior of the hot-pressed Ti-46Al-2Cr-2Nb alloy was comparable to that of a vacuum casting Ti-41.7Al-8.3Nb-0.09Y alloy measured under the same conditions for comparative purposes.