Surface layer for the working surface of the cylinders of a cumbustion engine and process of applying the surface layer

Abstract

A surface coating of the working surface of a cylinder of a combustion engine is disclosed, having the combination of the following characteristics: The coating is applied by plasma spraying; the surface of the coating comprises a plurality of open pores; the degree of porosity of the surface of the coating amounst to between 0.5 and 10%; the statistic mean pore size amounts to between 1 and 50 μm, whereby at least nearly exclusively pores with a size of less than 100 μm are present; the pores are stochastically distributed in the surface of the coating, both as far as the area and the size is concerned; the coating comprises a content of bound oxygen of between 0.5 and 8% by weight; the coating comprises inclusions of FeO and Fe3O4 crystals, serving as solid lubricants; and the roughness of the surface of the coating is adjusted by mechanically finishing to an arithmetic mean roughness Ra of between 0.02 and 0.4 μm and to a mean peak-to-valley distance Rz of between 0.5 and 5 μm. The pores form a plurality of micro chambers, supporting the build-up of an oil film between piston rings and cylinder wall.

Dependencies are inferred from the claim text.