Coating Bores of Light Metal Engine Blocks with a Nanocomposite Material using the Plasma Transferred Wire Arc Thermal S
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JTTEE5 17:344–351 DOI: 10.1007/s11666-008-9188-y 1059-9630/$19.00 Ó ASM International
Coating Bores of Light Metal Engine Blocks with a Nanocomposite Material using the Plasma Transferred Wire Arc Thermal Spray Process K. Bobzin, F. Ernst, J. Zwick, T. Schlaefer, D. Cook, K. Nassenstein, A. Schwenk, F. Schreiber, T. Wenz, G. Flores, and M. Hahn (Submitted September 7, 2007; in revised form April 25, 2008) Engine blocks of modern passenger car engines are generally made of light metal alloys, mostly hypoeutectic AlSi-alloys. Due to their low hardness, these alloys do not meet the tribological requirements of the system cylinder running surface—piston rings—lubricating oil. In order to provide a suitable cylinder running surface, nowadays cylinder liners made of gray cast iron are pressed in or cast into the engine block. A newer approach is to apply thermal spray coatings onto the cylinder bore walls. Due to the geometric conditions, the coatings are applied with specifically designed internal diameter thermal spray systems. With these processes a broad variety of feedstock can be applied, whereas mostly lowalloyed carbon steel feedstock is being used for this application. In the context of this work, an iron-based wire feedstock has been developed, which leads to a nanocrystalline coating. The application of this material was carried out with the Plasma Transferred Wire Arc system. AlMgSi0.5 liners were used as substrates. The coating microstructure and the properties of the coatings were analyzed.
Keywords
automotive industry, engine block, nanocrystalline coatings, Plasma Transferred Wire Arc
1. Introduction Two of the most important objectives of the automotive industry in the near future are the reduction of emissions and the reduction of fuel consumption. Both objectives depend on lowering not only the engineÕs weight but also the frictional resistance within the engine. Decreasing the engineÕs weight is obtained by the use of light-metal alloys. Gray cast iron, which was once the standard material in the production of engine blocks, is now often replaced by, mostly hypoeutectic, AlSi-alloys. Engine blocks made of those alloys save up to 50% in weight compared to those made of gray cast iron (Ref 1). The mechanical properties such as YoungÕs modulus, tensile strength, and hardness of aluminum-based alloys K. Bobzin, F. Ernst, J. Zwick and T. Schlaefer, Surface Engineering Institute, RWTH Aachen, Aachen, Germany; D. Cook, Flame-Spray Industries, Inc., Port Washington; K. Nassenstein and A. Schwenk, GTV Verschleiss-Schutz GmbH, Luckenbach, Germany; F. Schreiber and T. Wenz, DURUM VerschleissSchutz GmbH, Willich, Germany; G. Flores, Gehring GmbH & Co. KG, Ostfildern, Germany; and M. Hahn, Institut fu¨r Produkt Engineering - Lehrstuhl fu¨r Werkstofftechnik, Duisburg-Essen University, Duisburg, Germany. Contact e-mail: schlaefer@iot. rwth-aachen.de.
344—Volume 17(3) September 2008
used for engine blocks are significantly lower than those for gray cast iron. Particularly due to the low hardness, hypoeutectic A
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