Atmospheric characteristics in friction and wear of metals

Abstract

The effects of atmospheric gas molecules on the friction and the adhesive wear of metals are investigated for six pure metals: iron, titanium, cobalt, nickel, zinc and gold. In the experiments the relations between wear or friction and atmospheric pressure are studied in dry air, oxygen, and nitrogen at atmospheric pressures from 10 −5 to 10 5 Pa. From the experimental results the atmospheric characteristics in wear of metals are classified into three types according to the strength of activity in the chemisorption of gas molecules on the metal surfaces. When the gas molecules strongly chemisorb on the metal surfaces (Type I), the wear-atmosphere curve has a maximum point at a pressure between 10 −5 and 10 5 Pa as a result of the changes in wear mode. When the gas molecules weakly chemisorb on the metal surfaces (Type II), the wear increases with increasing atmospheric pressure. If the gas molecules do not chemisorb on the metal surfaces (Type III), the wear cannot change at any atmospheric pressure. The change of wear mode or the difference of wear volume between the pin and the disk specimen is explained by the effects of atmospheric gas on each metal surface.