ABSTRACT
Edoardo BEMPORAD 1, Marco SEBASTIANI and Fabio CARASSITI Mechanical and Industrial Engineering Department, University of Rome ‘Roma Tre’,
Via della Vasca Navale 79-00146 Rome, Italy;
Abstract. In the present paper, the adhesion, load bearing capacity and tribological performances of duplex coatings (Ti/TiN PVD and WC-Co HVOF) on Ti6Al4V substrate were investigated by experimental assessment of mechanical/tribological properties. Experimental activities consisted of nano-indentation testing, scratch testing and ball-on-disk sliding wear test under dry atmosphere. Morphology of the worn surface and layer failure mechanisms (i.e. sub-surface delamination, crack propagation modes, role of interfaces) were then analysed by FIB-SEM techniques. Results showed that the use of a WC-Co interlayer with intermediate hardness and stiffness provides a more effective distribution of contact strain, with an increase of load carrying capacity and wear resistance of the PVD coatings. A significant influence of the HVOF layer roughness on adhesion and failure modes was also detected. Furthermore, the presence of a Ti buffer layer also gives a significant improvement in adhesion of the PVD top layer, likely due to residual stress relaxation and improved crack propagation mechanisms due to the multilayered structure.
