Modification of the Railway Traction Elements.

This paper presents the results of research on a newly developed surface layer made by laser remelting the working surface of the Cu-ETP (CW004A, Electrolytic Tough Pitch) copper section insulator guide with Cr-Al powder. For the investigation, a fibre laser was used with relatively high power, reaching 4 kW, so as to ensure a high gradient of cooling rate for microstructure refinement. The microstructure of the transverse fracture of the layer (SEM) and the distribution of elements in the microareas (EDS) were investigated. The test results showed that chromium does not dissolve in the Cu matrix, and its precipitates take the shape of dendrites. The hardness and thickness of the surface layers as well as the friction coefficient and the influence of the Cr-Al powder feeding speed on them were examined. For the distance from the surface to 0.45 mm, the hardness of the produced coatings is above 100 HV 0.3 , while the friction coefficient of the produced coatings is in the range of 0.6-0.95. More sophisticated investigation results concern the d-spacing lattice parameters of the crystallographic structure of the obtained Cu phase reaching the range between 3.613-3.624 Å.