Application of Plasma Sprayed Cu Intermediate Layers in the Soldering Process of Graphite Composite to 6060 Aluminum Alloy

The work focuses on issues related to the soldering of graphite composite to 6060 aluminum alloy. The graphite composite is of great interest of the transportation industry as it is widely used in slides responsible for current collection from overhead catenary. The slides should meet various criteria resulting from relatively complex working conditions, e.g., in terms of electrical conductivity, self-lubricating, resistance to changing weather conditions, etc. Such an application has extensive requirements, mainly for a joint of graphite slide with aluminum body. The direct soldering of slide plates made of graphite composite to aluminum alloy collector head causes many technological problems and is not possible. In this study, the application of thin plasma sprayed (APS) copper intermediate layers is investigated for that purpose. After soldering process, the microstructural analysis confirmed the proper joint formulation, i.e., the soldering gap of 0.2 mm was well-filled with the solder over the entire width of joint. The soldered joints were then subjected for static shear testing. The obtained shear strength was in a relatively wide range of 13.04 to 20.50 MPa, which was influenced by various fracture mechanisms. Finally, the fact that reaction zones were not formed in investigated joints during soldering was confirmed by EDS analysis and micro hardness values, which were very similar to the ones of raw materials.