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A failure mode in engine components that undermines engine reliability is scuffing; defined as sudden catastrophic failure of sliding surfaces. Usually accompanied by a rapid rise in friction and temperature, occurrence of scuffing marks the end of the component's useful life. At Argonne National Laboratory, we recently developed low-friction amorphous carbon coatings with exceptional tribological properties. The present study evaluates the scuffing performance of three variations of the carbon coating deposited on H-13 steel surfaces and lubricated with base-stock and fully formulated synthetic Poly-alfa-olefin (PAO) lubricants. Using a ball-on-flat contact configuration in reciprocating sliding, we found that although the coatings reduced friction slightly, they increased scuffing resistance significantly when one of the sliding surfaces was coated when compared to uncoated steel-on-steel contact.

The U.S. Department of Energy has a program to develop fuel cell technology for automotive applications. For maximum efficiency, a fuel cell system requires a compact, light-weight, and highly efficient air compressor to provide a stream of clean air to the fuel cell stack. Meruit, Inc., is developing a turbocompressor for this application. Journal and thrust air bearings are two critical components of the turbocompressor that require low friction and excellent wear resistance. These components were coated with Argonne's new low-friction amorphous carbon coating and tested in an air bearing test rig. Results to date show that the coating provides the required friction reduction, as indicated by reduction in time to lift-off of the radial journal bearing during cyclic start/stop testing. The coating also prevented wall climbing which can cause bearing instability.

In contrast to conventional powertrains from internal combustion engine vehicles (ICEV), the tribological performance of powertrains of electric vehicles (EVs) must be further evaluated by considering new critical operating conditions such as electrical environments. The operation of any type of electric motor produces shaft voltages and currents due to various hardware configurations and factors. Furthermore, the common application of inverters intensifies this problem. It has been reported that the induced shaft voltages and currents can cause premature failure problems in tribological components such as bearings and gears due to accelerated wear and/or fatigue. It is ascribed to effects of electric discharge machining (EDM), also named, sparking wear caused by shaft currents and poor or increasingly diminishing dielectric strength of lubricants. A great effort has been done to study this problem in bearings, but it has not yet been the case for gears.

In an effort to reduce fuel consumption and emissions, hybrid vehicles incorporating fuel cell systems are being developed by automotive manufacturers, their suppliers, federal agencies (specifically, the U.S. Department of Energy) and national laboratories. The fuel cell system will require an air management subsystem that includes a compressor/expander. Certain components in the compressor will require innovative lubrication technology in order to reduce parasitic energy losses and improve their reliability and durability. One such component is the air bearing for air turbocompressors designed and fabricated by Meruit, Inc. Argonne National Laboratory recently developed a carbon-based coating with low friction and wear attributes; this near-frictionless-carbon (NFC) coating is a potential candidate for use in turbocompressor air bearings. We presents here an evaluation of the Argonne coating for air compressor thrust bearings.