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Twin-Wire Arc Spraying to Coat Engine Cylinders

July 12, 2012
Twin-Wire Arc Spraying to Coat Engine Cylinders Robert Brooks 07/12/2012 Material science addresses many of the problems of emerging product and process designs — but just as frequently the new materials present manufacturing challenges for OEMs and their supply-chain partners.

Material science addresses many of the problems of emerging product and process designs — but just as frequently the new materials present manufacturing challenges for OEMs and their supply-chain partners. For example, aluminum and magnesium-alloy engine blocks are designed to be lightweight, to achieve fuel-economy by reducing a vehicle’s mass, and to provide high strength to withstand the loads imparted by the combustion process. But, while these lighter materials address some requirements of modern engine construction, the quality of the cylinder surfaces emerges as a significant problem area for combustion engines.

The process Heller is standardizing melts iron/carbon wires and uses gas to spray the molten metal onto the surfaces of engine cylinders — to improve combustion efficiency in automotive engine blocks.

While surface hardness, roughness, and texture are important factors determining the rate fuel consumption, they also affect the performance of the engine. A cost-effective alternative technology to specialty cylinder liners is gaining attention: twin-wire arc spraying for coating cylinder bore surfaces of combustion engines. In co-operation with Daimler AG and others, Gebr. Heller Maschinenfabrik GmbH is taking on the task of industrializing all steps of the process and ensuring its process-reliable and cost-effective integration into engine production.

Heller specializes in milling machines and production systems for crankshafts and tool-and-die manufacturing.

Weight reduction and engine downsizing are among the most common measures used by automotive manufacturers to lower fuel consumption and CO2 emissions. Another way to increase efficiency is to reduce friction losses. For example, Daimler and its high-performance engine building subsidiary AMG are pursuing a new arc-spraying technology called Nanoslide® to coat cylinder bore surfaces and aluminum automotive crankcases.

Nanoslide is a twin-wire arc spraying process that melts iron/carbon wires and sprays them onto the cylinder surfaces of an aluminum crankcase, with the help of a gas flow. Compared to other thermal coating processes, the technology is considered highly cost-effective and technologically superior. However, finished product quality requires optimal calibration of current, voltage, wire feed, process gas flow, and other quality-determining parameters.

In 2005, AMG's M156 V8 engine provided a good example of the high efficiency the technology provides. Due to the engine’s thermally coated cylinder liners, they offer better displacement and torque, especially compared to similar aspirated engines that incorporate conventional lining technology. As such, it has been used on all 6.3-liter AMG engines from 2006 onwards.

About the Author

Robert Brooks | Content Director

Robert Brooks has been a business-to-business reporter, writer, editor, and columnist for more than 20 years, specializing in the primary metal and basic manufacturing industries. His work has covered a wide range of topics, including process technology, resource development, material selection, product design, workforce development, and industrial market strategies, among others. Currently, he specializes in subjects related to metal component and product design, development, and manufacturing — including castings, forgings, machined parts, and fabrications.

Brooks is a graduate of Kenyon College (B.A. English, Political Science) and Emory University (M.A. English.)