Characterization of Friction Riveting Dissimilar Joints with Ti Pins obtained through Selective Laser Melting with Polyetherimide Polymer

Abstract

In the present work, the study is focused on one of the types of thermomechanical anchoring joint known as friction riveting or FricRiveting. This technique was first patented by Helmholtz-Zentrum Geesthacht (HZG) - Germany in 2007. The joining process has three main stages: friction, forging and consolidation.The use of polymeric materials in the automotive, aeronautical, aerospace, naval and wind energy industries has been gaining interest in recent years since parts made of some thermoplastics, resins and composite materials with a polymeric matrix have low weight, good specific strength (strength- to-weight ratio), high resistance to fracture and recyclability (in the case of thermoplastics). Thus, the tendency is for hybrid polymer-metal structures to be produced more frequently in various industrial sectors, requiring the joining of dissimilar materials, which implies the search for joining techniques that present good mechanical response.Titanium alloys, whether of the a type (c.p. Ti) or a+² such as the Ti-6Al-4V alloy used in aeronautical applications, or as metallic biomaterials for implants, have excellent mechanical properties combining high mechanical strength (sUTS = 936 and 1014 MPa), atigue resistance limit of up to sfat = 510 MPa, combined with a low density, d = 4,42 g/cm³ and high specific mechanical strength (s/d).In this context, the objective of this work is to characterize dissimilar joints produced through Friction Riveting (friction riveting) between pins of a titanium alloy (Ti c.p. or Ti-6Al-4V) obtained through Laser Additive Manufacturing (SLM) and a polymer, to evaluate the feasibility of producing near net shape pins and their properties in the joint obtained. The characterization techniques that will be used are: optical microscopy (OM), scanning electron microscopy (SEM), DSC thermal analysis for the alloy and polymer (and also for the material adjacent to the joint after welding, which may present some modification/ structural degradation), X-ray diffraction (XRD) for the metallic alloy, in-line Vickers microhardness test along the interface or microhardness mapping, in order to provide an understanding of the transformations occurred in the polymer and in the interface of the welded dissimilar joint . We will also try to select the best SLM parameter for the pin and compare the effect of thermomechanical deformation with Ti alloys produced by the conventional casting and/or forging process.