Titanium and its alloys are extensively used in aerospace and mechanical applications because of their high specific strength and fracture toughness. On the other hand, titanium alloys often show poor resistance to sliding wear, low hardness and load bearing capacity, so that surface performance improvement is often recommended. Present work deals with design, production and characterization of a duplex coating system for Ti6Al4V components (i.e. crankshafts, piston rings, connecting rods) consisting of an high velocity Oxygen fuel (HVOF) WC-Co interlayer and a Ti/TiN multilayer (two layer pairs) deposited by cathodic arc evaporation - physical vapour deposition (CAE-PVD). A preliminary coating design was carried out, based on Finite Element simulation of residual stress fields on the PVD coating for a range of configurations of its multilayered structure (Ti buffer layer position and thickness). After the choice of the optimal PVD coating configuration, the influence of HVOF WC-Co substrate roughness on PVD adhesion on cylindrical components was analysed, with the aim of optimising the cost to performance ratio of the coating system. Morphological properties of the produced coatings (thickness, roughness, grain size, interfaces) were measured by means of Scanning Electron (SEM) and Focused Ion Beam (FIB) microscopy techniques, while mechanical properties were investigated using Rockwell C adhesion test, micro-scratch, micro- and nano-indentation techniques. The use of a multilayer Ti/TiN PVD coating, which thicknesses and Ti distribution were suggested by Finite Element Modelling, lead to a significant increase (about 60%) in adhesion to the HVOF coating, compared to monolayer TiN, without reduction in superficial hardness. Furthermore, the maximum allowed HVOF coating surface roughness (Ra) for an optimal adhesion of the PVD coating has been evaluated.
Bemporad, E., Sebastiani, M., Carassiti, F., Casadei, F., Valle, R. (2007). DEVELOPMENT OF A DUPLEX COATING PROCEDURE (HVOF AND PVD) ON TI-6AL-4V SUBSTRATE FOR AUTOMOTIVE APPLICATIONS. In Ceramic Engineering and Science Proceedings (pp.145-158). Uwe Schulz, Hua-Tay Lin [10.1002/9780470339510.ch15].
DEVELOPMENT OF A DUPLEX COATING PROCEDURE (HVOF AND PVD) ON TI-6AL-4V SUBSTRATE FOR AUTOMOTIVE APPLICATIONS
BEMPORAD, Edoardo;SEBASTIANI, MARCO;CARASSITI, Fabio;
2007-01-01
Abstract
Titanium and its alloys are extensively used in aerospace and mechanical applications because of their high specific strength and fracture toughness. On the other hand, titanium alloys often show poor resistance to sliding wear, low hardness and load bearing capacity, so that surface performance improvement is often recommended. Present work deals with design, production and characterization of a duplex coating system for Ti6Al4V components (i.e. crankshafts, piston rings, connecting rods) consisting of an high velocity Oxygen fuel (HVOF) WC-Co interlayer and a Ti/TiN multilayer (two layer pairs) deposited by cathodic arc evaporation - physical vapour deposition (CAE-PVD). A preliminary coating design was carried out, based on Finite Element simulation of residual stress fields on the PVD coating for a range of configurations of its multilayered structure (Ti buffer layer position and thickness). After the choice of the optimal PVD coating configuration, the influence of HVOF WC-Co substrate roughness on PVD adhesion on cylindrical components was analysed, with the aim of optimising the cost to performance ratio of the coating system. Morphological properties of the produced coatings (thickness, roughness, grain size, interfaces) were measured by means of Scanning Electron (SEM) and Focused Ion Beam (FIB) microscopy techniques, while mechanical properties were investigated using Rockwell C adhesion test, micro-scratch, micro- and nano-indentation techniques. The use of a multilayer Ti/TiN PVD coating, which thicknesses and Ti distribution were suggested by Finite Element Modelling, lead to a significant increase (about 60%) in adhesion to the HVOF coating, compared to monolayer TiN, without reduction in superficial hardness. Furthermore, the maximum allowed HVOF coating surface roughness (Ra) for an optimal adhesion of the PVD coating has been evaluated.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
