September 15, 2004

Laser Process: Research Team Including Audi Engineer Nominated for the "German Future Prize"
Source: Audi
AG

A research group including Horst Lindner, responsible for the development of production processes at AUDI AG, has been nominated for the "German Future Prize 2004" - the German President's prize for technology and innovation - for a new type of machining process in engine production. The "exposure of the cylinder bores of internal combustion engines to UV laser light" reduces engine oil consumption by up to 75 %, and wear to the cylinder bores and piston rings by as much as 90 %. The process is already in use for series production at Audi's Hungarian plant in Györ. The 3.0 TDI diesel engines that are already being installed in the Audi A6 and the Audi A8, and that will shortly also be supplementing the range of engine options for the VW Phaeton and the VW Touareg, are produced there using this machining process.

In explanation: Grey cast iron (cast iron with lamellar graphite) is probably one of the most important materials in engine-building. And cylinder bores must be as smooth as possible. Ideally, though, this smooth surface should also have a structure that simultaneously holds the engine oil in place. This balancing act is achieved with the aid of a UV laser. It literally "vaporizes" the top layer of the cylinder bore. The graphite deposits in the material are exposed, and countless, microscopically small "hollows" are formed, in which the oil can collect. Furthermore, the laser pulse melts the surface in place. When the laser pulse ends, the layer instantaneously solidifies into a nanocrystalline structure, which gives the surface of the bore ceramic properties as a result of its high nitrogen content.



In this way the surface is provided with the optimum sliding properties and wear is significantly reduced. The heat of combustion when the engine is running also contributes to improving resistance to wear. This is because the structure is given "superplastic" properties by the application of heat - it gives more easily. In effect, this "give" makes it significantly more difficult for the atoms to become detached from their atomic bond, and resistance to wear increases tremendously.

Lindner: "This self-conditioning effect is a tribological revolution. The surface is transformed as if of its own accord." Wear is reduced by up to 90 %.

One other positive side effect: The oil is retained better in the material's natural surface structure exposed by the laser. This results in a tremendous reduction in oil consumption, because the piston ring no longer distributes so much oil on the cylinder wall of the combustion chamber. This is associated with better emissions figures, because the exhaust gases contain less oil in the form of unburned hydrocarbon. Savings of up to 75 % can be achieved in oil consumption.

Other members of the UV laser process project group nominated for the German Future Prize, in addition to Lindner, are the physicist Robert Queitsch of the ATZ Development Centre for Process Engineering, and the recently deceased Prof. Hans W. Bergmann of the Chair of Metallic Materials at the University of Bayreuth. On 11th November President Horst Köhler will announce in Berlin which of the four nominated teams of researchers will be awarded the prize.

This is already the second nomination of Audi employees for this renowned award. In 2002 two engineers from the Audi Group also ranked among the top four in the context of a cooperative project. On that occasion it was for the development of an optoelectronic processor, enabling a vehicle to "see" in three dimensions.