Author(s)

M. Tercelj, I. Perus & G. Kugler

Abstract

The study of wear of a tribological pair of soft and heated metals in contact with a hard counter body is very demanding. So far, less attention has been devoted to this problem and thus progress in this field is needed. In Al hot extrusion also the mentioned tribological system prevails but it is also supposed that various contact pressures between extruded Al die bearing surfaces takes place. In order to explain wear behaviour on die bearing surfaces wear tests of nitrided surfaces at low, medium and higher contact pressures using block on cylinder test equipment were carried out. Tested surfaces at medium contact pressures exhibit some significances obtained at testing at lower as well as at higher contact pressures. Essentially, the difference at medium contact pressure is higher density of partial removal of compound layer on spots of its previous initial cracking in comparison to lower contact pressure. At higher contact pressure removal of the compound layer is already preferentially oriented in the sliding direction in the first stage, while at medium contact pressure this is observed only in later stages of the degradation progress. Keywords: aluminium hot extrusion, die wear progress, nitrided microstructures, compound layer, cracking. 1 Introduction Hot extrusion is normally used for forming long Al products, like rods, beams, wires, etc. Over 95% of all extrusion dies are gas nitrided since application of PVD coatings has some limitations due to \“line-of-sight” effect at coating in narrow gape of complex shaped dies. In order to increase the service time of the

Keywords

aluminium hot extrusion, die wear progress, nitrided microstructures, compound layer, cracking