Insulated Rail Joints for Signalling Applications

Abstract

Insulated rail joint assemblies provide electrical insulation between two sections of rail for signalling purposes. In this work, rail steel was successfully bonded to PSZ ceramic using an active brazing technique. In order to increase the wettability of the PSZ ceramics, titanium coating was deposited on the ceramic surface using a filtered arc deposition system. A filler metal called BVAg-18 (60%Ag-30%Cu-10%Sn) was used and the joining was performed at a temperature of 750 °C. Bonding between partially stabilised zirconia and rail steel with BVAg-18 filler metal was not achieved using a standard brazing method. Bonding did occur with the BVAg-18 filler metal using the advanced brazing technique of active metal brazing, with best results obtained using a brazing temperature of 750oC and a dwell time of 10 minutes. The microstructure of the coating and joint interface were characterised by XRD, SEM and EDS.