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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.

The application of polyalkylene glycol (PAG) as a base stock for engine oil formulation has been explored for substantial fuel economy gain over traditional formulations with mineral oils. Various PAG chemistries were explored depending on feed stock material used for manufacturing. All formulations except one have the same additive package. The friction performance of these oils was evaluated in a motored single cylinder engine with current production engine hardware in the temperature range 40°C-120°C and in the speed range of 500 RPM-2500 RPM. PAG formulations showed up to 50% friction reduction over GF-5 SAE 5W-20 oil depending on temperature, speed, and oil chemistry. Friction evaluation in a motored I-4 engine showed up to 11% friction reduction in the temperature range 40°C-100°C over GF-5 oil. The paper will share results on ASTM Sequence VID fuel economy, Sequence IVA wear, and Sequence VG sludge and varnish tests. Chassis roll fuel economy data will also be shared.

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.

Amorphous carbon coatings with very low friction properties were recently developed at Argonne National Laboratory. These coatings have shown good promise in mitigating excessive wear and scuffing problems associated with low-lubricity diesel fuels. To reduce the negative effect of sulfur and other lubricant additives in poisoning the after-treatment catalyst, a lubricant formulation with a low level of sulfur may be needed. Exclusion of proven sulfur-containing extreme pressure (EP) and antiwear additives from oils will require other measures to ensure durability of critical lubricated components. The low-friction carbon coating has the potential for such applications. In the present study, we evaluated the friction and wear attributes of three variations of the coating under a boundary lubrication regime. Tests were conducted with both synthetic and mineral oil lubricants using a ball-on-flat contact configuration in reciprocating sliding.

Increased use of higher-efficiency compression ignition direct injection (CIDI) diesel fueled engines instead of today's gasoline engines will result in reduced fuel consumption and greenhouse gases emissions. However, nitrogen oxides (NOx) and particulate exhaust emissions from diesel engines must be significantly reduced due to their possible adverse health effects. Exhaust gas recirculation (EGR) is an effective way to reduce NOx emissions from diesel engines, but the particulates and acidic exhaust products in the recirculated gas will contaminate engine lubricant oil by increasing the soot content and total acid number (TAN). These factors will increase the wear rate in many critical engine components and seriously compromise engine durability. We have investigated the use of commercially available thin and hard coatings (TiN, TiCN, TiAlN, and CrN) to mitigate the negative effects of EGR on wear.

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.

In this paper, we will demonstrate the effectiveness and usefulness of a new class of superlow-friction carbon films in alleviating the wear and scuffing problems associated with the use of low-sulfur diesel fuels in fuel delivery systems of advanced diesel engines. Specifically, using a well-established diesel fuel lubricity test machine, we will show that with the use of very thin (1 μm thick), super lubricious carbon films, one can restore lubricity and virtually eliminate scuffing and potential wear failures that can occur in low-sulfur, super-clean, and zero-sulfur (Fischer-Tropsch) diesel fuels. Test results from our study raise the prospect for using such carbon coatings to solve problems associated with the use of low-sulfur diesel fuels and high injection pressures in future engines.

An increase in engine and vehicle efficiency usually requires an increase in the severity of contact at the interfaces of many critical components. Examples of such components include piston rings and cylinder liners in the engine, gears in the transmission and axle, bearings, etc. These components are oil-lubricated and require enhancement of their tribological performance. Argonne National Laboratory (ANL) recently developed a carbon-based coating with very low friction and wear properties. These near-frictionless-carbon (NFC) coatings have potential for application in various engine components for performance enhancement. This paper presents our study of the tribological performance of NFC-coated steel surfaces when lubricated with fully formulated and basestock synthetic oils. The NFC coatings reduced both the friction and wear of lubricated steel surfaces. The effect of the coating was much more pronounced in tests with basestock oil.

The sulfur content in diesel fuel has a significant effect on diesel engine emissions, which are currently subject to environmental regulations. It has been observed that engine particulate and gaseous emissions are directly proportional to fuel sulfur content. With the introduction of low- sulfur fuels, significant reductions in emissions are expected. The process of sulfur reduction in petroleum-based diesel fuels also reduces the lubricity of the fuel, resulting in premature failure of fuel injectors. Thus, another means of preventing injector failures is needed for engines operating with low- sulfur diesel fuels. In this study, we evaluated a near-frictionless carbon (NFC) coating (developed at Argonne National Laboratory) as a possible solution to the problems associated with fuel injector failures in low-lubricity fuels.

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.

While sulfur in diesel fuels helps reduce friction and prevents wear and galling in fuel pump and injector systems, it also creates environmental pollution in the form of hazardous particulates and SO2 emissions. The environmental concern is the driving force behind industry's efforts to come up with new alternative approaches to this problem. One such approach is to replace sulfur in diesel fuels with other chemicals that would maintain the antifriction and antiwear properties provided by sulfur in diesel fuels while at the same time reducing particulate emissions. A second alternative might be to surface-treat fuel injection parts (i.e., nitriding, carburizing, or coating the surfaces) to reduce or eliminate failures associated with the use of low-sulfur diesel fuels. Our research explores the potential usefulness of a near-frictionless carbon (NFC) film developed at Argonne National Laboratory in alleviating the aforementioned problems.