Ricardo UK Ltd
The main aim of the research is to examine the mechanisms of formation of wear protective oxide films known as 'glazes' in relation to rotation speed, temperature, time and pre-treatments in an unlubricated bearing environment. Once 'glazes' form they provide low friction and high wear resistant surfaces possibly preventing the need for oil lubrication.
Previous investigations have shown that the formation of these protective films occurs during the wear of certain alloys under specific speed, load and temperature conditions. However, none of these investigations have been made in a bearing geometry. SEM and EDX analysis of the worn surfaces and wear debris will be used to help investigate the mechanisms of wear protective film formation. Additionally weight recordings, friction coefficient data, talysurf measurements, and diameter measurements will all be used to assess the ability of the in preventing bearing wear. The testing will take place using a specially designed high temperature bearing rig and a variety of different alloys will be investigated.
From this research it is hoped to show that with the correct alloys and possibly surface pre-treatment, an unlubricated bearing can be produced for use in a number of different applications such for turbocharger bearings.
An unlubricated bearing would have the following advantages:
• Reduced environmental impact as the quantity of oil required in an engine would be reduced. In addition, the oil change service intervals could be increased as lubricated oil would not be degraded by the hot turbocharger on turbocharged engines. Another ‘green’ benefit is that the hydrocarbon emissions will be lower as lubricating oil would not escape through the turbo bearing into the exhaust gases
• Reduced warranty costs due to robustness to lack of oil lubrication, oil contamination issues
• Reduced component, machining, assembly costs and oil supply not required to bearing