Tetrahedral Amorphous Carbon Coatings for Friction Reduction of the Valve Train in Internal Combustion Engines

Abstract

Tetrahedral amorphous carbon (ta-C) is studied as a tribological coating for the valve train's exhaust camshaft of a combustion engine. The coated camshafts were installed in a non-fired engine, tested in a computerized component test bench under practice-relevant conditions and analyzed for their frictional behavior. A notable reduction of the valve train's drive torque on the test bench is demonstrated. Namely, on a roller cam system with ta-C-coated camshaft the reduction is about 15% in average within the entire engine-map. The ta-C coatings were extensively characterized under laboratory conditions before and after the investigations on the test bench. Mechanistic understanding of the tribological behavior of ta-C coatings under dry or starving lubricated conditions was achieved by atomistic simulations of the tribological contact. Industrial utilization of these results would lead to a significant increase of the energy efficiency of combustion engines.

Microanalysis of Worn Surfaces of Selected Rotating Parts of an Internal Combustion Engine

“…The opening surfaces of the cams ( Figure 5 , opening and closing ramps) appear to be problem free, because the largest forces act on the surfaces of the cams due to the acceleration of the valves [ 17 ]. Due to the large radius of the curvature of the cam, the surfaces of the cams and the tappet are sufficiently separated by the lubricating film, which is also due to the high entrainment speed of the lubricant [ 18 , 19 , 20 ].…”

Wear Mechanism of Superhard Tetrahedral Amorphous Carbon (ta‐C) Coatings for Biomedical Applications

“…[ 6–8 ] With the advancements in large‐scale physical vapor deposition (PVD) coating technology, ta‐C coatings gained relevance for many applications in the field of cutting and forming tools or engine components. [ 9–11 ]…”

“…[6][7][8] With the advancements in large-scale physical vapor deposition (PVD) coating technology, ta-C coatings gained relevance for many applications in the field of cutting and forming tools or engine components. [9][10][11] Tetrahedral amorphous carbon (ta-C) coatings have the potential to protect biomedical implants from wear and increase their service life. This study elucidates the biocompatibility, mechanical properties, adhesion, and wear resistance of ta-C coatings fabricated by physical vapor deposition on cobaltchromium-molybdenum (CoCr) and titanium (Ti64) alloys as well as ultrahigh molecular weight polyethylene (UHMWPE).…”

External magnetic field guiding in HiPIMS to control sp3 fraction of tetrahedral amorphous carbon films

“…ta-C coatings exhibit excellent resistance to corrosion, wear, and biofouling [1][2][3][4][5] and have chemical inertness and biocompatibility [6,7]. These coatings have become increasingly popular for a wide variety of industrial and commercial applications including machine parts [8,9], bearings [10], microelectromechanical devices, biomedical instruments and sensors [6,[11][12][13].…”