TY - JOUR A1 - Woydt, Mathias T1 - Tribological characteristics of polycrystalline Magnéli-type titanium dioxides JF - Tribology letters N2 - The results presented in this paper have clarified experimentally, that titania-based Magnéli-phases (Ti4O7/Ti5O9 and Ti6O11) with (121)-shear planes exhibit more anti-wear properties than lubricious (low-frictional) properties. The results for dry sliding indicate that the coefficients of friction lie in the range of 0.1–0.6 depending on sliding speed and ambient temperature. The COF decreased with increasing temperature (T= 22–800°C) and increasing sliding speed (?= 1-6 m/s). The dry sliding wear rate was lowest for the Al2O3 at 1 m/s at 800°C with values of 1.7 × 10-8 and 6.4 × 10-8 mm3/N m, comparable to boundary/mixed lubrication, associated with a high dry frictional power loss of 30 W/mm2. The running-in wear length and, more important, the wear rate decreased under oscillating sliding tests with increasing relative humidity. The contact pressure for high-/low-wear transition increased under oscillating sliding tests with increasing relative humidity. At room temperature and a relative humidity of 100% the steady-state wear rate under dry oscillating sliding for the couple Al2O3/Ti4O7–Ti5O9 was lower than 2 × 10-7 mm3/N m and therefore inferior to the resolution of the continuous wear measurement sensor. TEM of wear tracks from oscillating sliding revealed at room temperature a work-hardening as mechanism to explain the running-in behavior and the high wear resistance. The hydroxylation of titania surfaces favours the high-/low-wear transition. KW - Magnéli-phases KW - Shear planes KW - Planar defects KW - Ceramics KW - Dry friction KW - High temperature KW - Titania KW - Wear KW - Work-hardening KW - TEM KW - Humidity PY - 2000 DO - https://doi.org/10.1023/A:1019170831371 SN - 1023-8883 SN - 1573-2711 VL - 8 SP - 117 EP - 130 PB - Springer Science Business Media B.V. CY - Dordrecht AN - OPUS4-2443 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -