Improvement in friction by cw Nd:YAG laser surface treatment on cast iron cylinder bore

The reduction of the oil-film thickness in the piston-assembly of automobile engines has lead to it now being necessary to add a cylinder-bore surface treatment, so that oil reserves can be created on it. However in doing this, the initial plateaued texture must be kept. With a Nd:YAG laser source treatments oil reserves holes are formed, which respect the function of the initial bore surface texture. The material, cast iron, is heterogeneous: perlitic matrix and carbon lamellae. The laser treatment will make use of this heterogeneity: as under a cw laser beam, using graphite, with its good insulating material properties, carbon lamellae, which are near the surface, are revealed. Also a high density of lamellae in a hollow against the surface are obtained. In order to improve these new surfaces, friction tests were conducted on a friction bench using samples from engine components as test pieces. In order to know bore roughness evolution, 3D surface topography measurements were made before and after as well as friction tests on surfaces without laser treatment and with laser treatment. The results indicate that these holes can improve oil lubrication time. (C) 2002 Elsevier Science B.V. All rights reserved.