Diesel engines are among the world’s most significant contributors to fossil fuel in the transportation sector. Post-treatment of mechanically honed Diesel engine cylinder liners with UV photons of a high power 308 nm excimer laser and nitrogen-assist gas lead to wear-reduction of up to 85 % for both the cylinder liners and the piston rings. Moreover, the oil consumption is reduced by ~75 % compared to employing conventional mechanically honed cylinder surfaces. The hardened excimer laser modified surface shows less friction and wear and significantly contributes to less fuel and oil consumption, and hence more efficient Diesel engines. LAMBDA SX-Series Excimer Lasers
In the 308 nm surface hardening process, an engine block is positioned in a workstation incorporating the LSX excimer laser operating at 300W average output power. Beam-delivery optics direct the excimer laser beam at the cylinder wall and scan the wall along the length of the cylinder. A nitrogen-assist gas is applied during laser irradiation. UV excimer laser treatment produces three effects that contribute to wear reduction. First, the surface is molten to a depth of about 2µm, allowing overall smoothing of the surface. Second, a hard nitride layer is formed, which is still present even after 800 h of engine operation. And, most important, a micro-hydrodynamic structure is formed due to the opening of graphite cavities. The resulting pits act as tiny wells that capture the lubricant, resulting in a unique tribological effect. Reduction of wear of up to 85% and of oil-consumption of up to 75% is obtained under various conditions.

Fig. 1 - Micrograph of hydrodynamic structure before (left) and after 308nm excimer laser treatment (right).

Click on image for larger view. Fig. 2 - Wear-reduction for an excimer laser-treated engine versus a conventionally honed engine.

The excimer laser surface modification improves fuel efficiency and decreases long-term wear, thereby reducing oil consumption and particulate emissions helping to save our resources and to protect our climate. For the engine manufacturer this also means he can easier meet legislation demands.

Material	Metal
Process	Surface Modification