Geometric effects in high‐temperature vapour‐phase lubrication using hydrocarbon feed gases

Abstract

AbstractThe effectiveness of ‘far‐field’ vapour‐phase lubrication, in which areas of a bearing surface that are cycled through the contact are exposed to vapour while outside the contact, has been demonstrated in both sliding and combined roll slide tests using acetylene vapours to deposit pyrolytic graphite. Friction coefficients as low as μ = 0.008 have been measured for steel at 540°C with far‐field acetylene concentrations as low as 5%. Effective vapour‐phase lubrication depends on solid lubricant deposition that exceeds the contact's capacity to remove solid lubricant through wear. While the rate of removal is increased by increasing the sliding velocity, in far‐field vapour‐phase lubrication the rate of lubricant deposition, and therefore the lubrication effectiveness, is augmented by increased areas available for far‐field deposition, such as those provided by performing wear tests with increased wear‐track diameters. These geometric concepts may be considered in rolling‐element bearing and gear set applications where vapour‐phase lubrication is to be employed.