Method of making wear-resistant cylinder, or cylinder liner surfaces

Claim 1

Method of improve the wear resistance of running surfaces of cylinders or cylinder liners, made of cast iron, for an internal combustion engine, in which the cylinder bore is machined to a diameter which is slightly less than the desired final diameter and the cylinder bore wall is subsequently hardened by impinging a laser beam thereon, wherein an absorption substance is applied to the surface of the cylinder bore which has the characteristic of lowering the reflection of laser light to provide for absorption of energy furnished by the laser beam, and the cylinder bore wall is hardened by impinging the laser beam on the cylinder bore and relatively moving the laser beam and the bore wall in a track pattern to obtain hardened tracks (4) in which the edge zones will have martensitic structure and, after hardening, the wall of the cylinder bore is honed to the final desired diameter, wherein the step of hardening the cylinder bore wall by the laser beams is carried out by guiding the laser beam in hardening tracks (4) extending parallel to each other along the wall (2) of the cylinder or the cylinder liner, and at an inclination with an acute angle (α) with respect to the axis of the cylinder (3), said laser beam causing internal tension stresses to arise adjacent the hardening tracks within the material of the cylinder bore proximate to the cylinder bore walls; and wherein the hardening tracks (4) are applied to leave a spacing or gap X between the edges of the two adjacent hardening tracks (4), which spacing is so dimensioned that the maxima (9, 10) of internal tension stresses occurring in the cylinder walls cannot overlap, said maxima of tension stresses being spaced by a distance L from the respective edges of the adjacent hardening tracks (4), and wherein X is greater than 2 k.