Cylinder liner of a hypereutectic aluminum/silicon alloy for casting

Abstract

The invention relates to a cylinder liner, cast into a reciprocating piston engine, of a highly hypereutectic aluminum/silicon alloy which is free of hard material particles independent of the melt and has such a composition that fine primary silicon crystals and intermetallic phases automatically form from the melt as hard particles. By spray-compacting, a blank of finely sprayed melt droplets is caused to grow, a fine distribution of the hard particles being produced by controlled introduction of small melt droplets. The blank can be transformed by an extrusion step into a form approximating the cylinder liner. After subsequent premachining with chip removal, the running surface is precision-machined and subsequently honed in at least one stage, after which the hard particles located in the running surface are exposed, plateau faces of the particles being formed, which faces protrude from the remaining surface of the matrix structure of the alloy. The exposing of the primary crystals and/or particles is effected chemically, using aqueous alkali. Owing to the fine-grained hard particles formed in the melt and to their large proportion in the matrix structure and owing to the exposing of the hard particles in the matrix structure, not only high wear resistance and a high load bearing proportion of the running surface result, but also the possibility of using inexpensive piston ring fittings and piston coatings with, at the same time, low oil consumption and correspondingly low hydrocarbon emissions.