Effect of leaser treatment on the surface of cast iron cylinder bores

Abstract

IntroductionThe environmental and pollution materials emission standards in Europe and worldwide are going to be more strict, and fuel prices are continuously increasing. These facts persuade the automotive engine developers to build more efficient and environmentally friendly engines. To meet environmental regulations and because of increasing fuel prices, it is expected that, even at higher engine power, the fuel and oil consumption should not increase. It is also obvious that the engines should have a long lifetime [1]. Both the consumption reduction and the power increase of Otto-or Diesel-engines cause higher pressures in the combustion chamber resulting higher tribological load and wear rate for the piston rings and to the cylinder bore [1]. Laser treatments are widely used for surface modifications, from surface alloying to surface shock hardening [2-5] to improve surface properties of sliding machine parts. Thus, laser surface treatments gain an increasing significance in the automotive industry. A wide range of automotive parts, from brake drums to engine parts [6][7][8][9][10], are laser treated to alter the surface and near surface properties of the materials. To improve the mechanical and tribological properties of different cylinder bores it is possible to use special mechanical treatment [11] or chemical coatings [12][13][14] and laser structuring treatments [15] or -which is used by a large European automotive manufacturer -a special laser surface treatment on the cast iron V-block engines to alter the properties of the cylinder bores. Due to the laser treatment, the area near the surface of the cylinder bore becomes harder and more wear resistant. Furthermore, due to the inhomogenity of the pearlitic matrix and carbon lamellae, oil reserving holes are formed. This treatment results in an increased power output and reduced oil consumption [1, 16].