Friction and wear of Al 2O 3, ZrO 2 and SiO 2 rubbed against pure metals

Abstract

The factors influencing friction and wear between metals and oxides have been discussed from the wear tests of seven kinds of pure metals (silver, platinum, copper, magnesium, iron, titanium, aluminium) and silicon rubbed against polycrystalline Al 2O 3 (alumina), ZrO 2 (zirconia) and SiO 2 glass in vacuum and in oxygen. The results indicated that the friction and wear are determined by the following three factors: (1) the oxidation activity of the metals; (2) the relative shear strength of the metal and oxide; and (3) atmospheric oxygen. In vacuum, the higher the oxidation activity of the metal, the higher friction it exhibited. The atmospheric oxygen increased the friction between oxides and metals with low oxidation activity, whereas it decreased the friction when the metals had high oxidation activity. The effect of atmospheric oxygen on the friction of platinum vs. Al 2O 3 and ZrO 2 has been studied in detail. With increased oxygen pressure, the coefficient of friction exhibited anomalous characteristics; it varied between 0.005 (in the case of Pt/Al 2O 3) and 0.7 as a function of oxygen pressure.