Effect of Surface Condition on the Formation of Solid Lubricating Films at High Temperatures

Abstract

Data are presented showing the effect of the surface condition of metals and ceramics on wear at high temperatures (280°C). When cast iron is heated to 280°C and subjected to reciprocating wear, a layer of Fe₃O₄ is formed on the surface which has a high coefficient of friction (0.68) and a high wear rate. To reduce this wear, a vapor stream of 0.1 percent tricresyl phosphate (TCP) and nitrogen was continuously delivered to the contact region between the pin and reciprocating plate. The coefficient of friction was reduced to 0.1 and the wear rate was essentially zero.

This reduction in wear was due to the formation of a polymeric derivative of original TCP on the high temperature surfaces. For ceramic materials the oxide coaling prevents the formation of the polymeric derivatives. High wear was observed even during vapor lubrication. By chemically treating the ceramic with ferric acetylacelonate, a thin layer of Fe₂O₃ (20 atoms thick) was formed on the ceramic. Continuous vapor phase lubrication of chemically treated Sialon reduced the coefficient of friction from 0.7 to less than 0.1 resulting in essentially no wear. This method of chemically treating materials for high temperature vapor phase lubrication has direct application for the operation of high temperature engines.

Presented at the 46th Annual Meeting in Montreal, Quebec, Canada April 29–May 2, 1991

KEY WORDS:

• Vapor
• Lubrication
• High Temperature
• Solid Lubricant
• Ceramics

Notes

Presented at the 46th Annual Meeting in Montreal, Quebec, Canada April 29–May 2, 1991