Lower frictional wear and oil consumption in IC engines by modifying the materials used in cylinder liners with UV laser exposure

(f.l.t.r.) Dipl.-Phys. Robert Queitsch, Dipl.-Ing. Horst Joachim Lindner

Dipl.-Ing. Horst Joachim Lindner (Spokesperson)
Prof. Dr.-Ing. habil. Hans Wilhelm Bergmann
Dipl.-Phys. Robert Queitsch

AUDI AG, Ingolstadt
Universität Bayreuth
ATZ Entwicklungszentrum, Amberg

Cylinders are the heart of an engine. They contribute the mechanical energy to drive a vehicle – but in the process they use plenty of oil and produce noxious emissions.
Can these disadvantages be avoided?

Horst Joachim Lindner, Hans Wilhelm Bergmann and Robert Queitsch have proven it can be done by using an UV laser to modify the material used in cylinder liners. Horst Lindner is a research associate for product and manufacturing methods at AUDI AG in Ingolstadt; Hans Wilhelm Bergmann holds a Chair for Materials Science at the University of Erlangen; Robert Queitsch is a research associate at ATZ Entwicklungszentrum in Sulzbach-Rosenberg.

Immense influence of the cylinder surface
Combustion engines produce drive by converting the chemical energy of fuel into mechanical power. How high power and consumption are largely depends on the structure of the cylinder surface. It serves as a slideway for piston rings and pistons and simultaneously seals the combustion chamber at the interface to the engine crankcase.

An important goal of development for car manufacture is to reduce fuel consumption. This is achieved by higher combustion pressures in the piston. Associated with this, however, are higher mechanical stresses on the cylinder liners and piston rings. In the past, the cylinder liner surfaces were treated by honing, a specific bore technology, to apply a special structure for oil retention. Consequently, however, a lot of oil is used. The result: vast amounts of unburned hydrocarbons are released with the exhaust. Moreover, the honing process also increases wear.

Laser pulses provide robustness
The team’s innovation is based on the large-area treatment of cast iron cylinder liners with an ultraviolet (UV) laser in the path of the piston rings. The laser pulses vaporize material on the cylinder walls. Graphite separations in the cast iron form a special surface structure. At the same time, the liner surface is melted, creating a plasma. Nitrogen is introduced to the molten layer which hardens in a nanocrystalline microstructure. This treatment makes the cylinder liner much more durable as it continues during use to turn into a fine structure with superplastic properties. The result: engine wear decreases. Oil consumption – and thus the emissions harmful to the environment – is considerably reduced.

The UV laser technology is now an integral part of series production of diesel engines at AUDI AG. It can also be applied for other machine parts made of cast iron or steel materials which are subjected to high mechanical stresses.