Effects of surrounding atmosphere on micro-hardness and tribological properties of sintered alumina

Using a nanoindentation technique, the environmental effects were studied on the micro-hardness of sintered alumina. Friction and wear properties were also examined under lubrication with the same liquids: pH adjusted water solutions with NaOH or HCl, methanol, acetone, benzene and n-hexane. A relationship between the wear properties and the hardness changes in organic compound liquids was observed. It is considered that the adsorption phenomena dominate these environmental effects. On the other hand, few differences in the micro-hardness due to the change of the pH values were observed. The friction and wear properties, however, showed obvious variation against the pH values. It is considered that the change of pH values affects dissolvable properties of the sliding surface.