High-Temperature Tribological Behavior of the Ti-22Al-25Nb (at. %) Orthorhombic Alloy with Lamellar O Microstructures

Tribological behavior of the isothermally forged and heat-treated Ti-22Al-25Nb (at. %) orthorhombic alloy with lamellar O microstructures was investigated. The friction experiments using a tribometer (UMT-3 CETR) against Si3N4 and Al2O3 were conducted at the load of 10N from 20 to 750 degrees C and a constant speed of 0.188 m/s. The experiment results indicated that for the friction pair of Al2O3, the coefficient of friction (COF) was decreased from 0.906-0.359, and for the friction pair of Si3N4, COF was decreased from 0.784-0.457 as the friction temperature increased from room temperature to 750 degrees C. The wear rate of the alloy against Al2O3 is in the range of 2.63-8.15 x 10(-4) mm(3) N(-1)m(-1), the wear rate against Si3N4 is in the range of 2.44-5.83 x 10(-4) mm(3)N(-1)m(-1), respectively. The wear mechanisms of the alloy were changed from plastic deformation and ploughing at lower temperature (20-400 degrees C) to adhesive wear and oxidative mechanism at higher temperature (600 and 750 degrees C). The friction and wear behavior of the Al2O3 friction pair was comparable to that of the Si3N4 friction pair.