Sliding Characteristics of Metals at High Temperatures

Friction tests were run with a number of metals sliding against themselves. With iron, copper, nickel, molybdenum and chromium, high friction and considerable surface damage resulted until a particular transition temperature was reached; above this temperature a considerable improvement in the sliding characteristics was observed. The transition temperature for the various metals was as follows: iron, 100–200 F; copper, 400–500 F; nickel, 1200–1400 F; molybdenum, 800–900 F; and chromium, 800–1100 F. This improvement was associated with the generation of oxide in the sliding track. When tested as lubricants a number of the metal oxides were effective in reducing friction and preventing surface damage. Since the softer oxides were the more effective it was hypothesized that metals which form these oxides would have the better sliding characteristics at high temperatures. The friction characteristics of alloys were compared with the frictional characteristics of the major constituents. Presented as an American Society of Lubrication Engineers paper at the Lubrication Conference held in New York, N.Y. October 1959.