# Laser Finishing of Ti6 Al4V Additive Manufactured Parts by Electron Beam Melting
## 1 Introduction  
Initially, three-dimensional (3D) printing was adopted just for rapid prototyping (RP); recently, it has been used as a real production technology, starting from the three-dimensional mathematical model, realized with CAD (computer aided design) software. The technique allows creating components by adding material \"layer-by-layer\". This is the reason why it is also known as additive manufacturing (AM) [1]. By using different AM techniques, it is possible to obtain customized and complex components of different materials (metals, plastic or ceramic) with competitive costs and times [2]. In the aeronautic field, the most attractive materials are definitely metals, such as titanium and aluminum alloys, as they allow to design components with very complex shapes that are hardly obtained when using conventional technologies [2; 3; 4]. Metal parts can be obtained using different AM techniques and are all based on power bed fusion (PBF) technology [1], such as electron beam melting (EBM) [5], direct metal laser sintering (DMLS) [4; 6], and selective laser melting (SLM) [7; 8]. However, the surfaces of the printed parts all have a low quality. The typical arithmetic average of the roughness profile (Ra) varies in the range 8-25 \(\upmu\)m [2; 6; 9] depending on the adopted technology. Even if lower values of roughness are obtainable by laser sintering/melting, the EBM process is generally preferred for the production of aerospace components as it can produce high-quality products with excellent mechanical properties and fewer defects compared to those achieved by using laser technologies. Thus, it is possible to obtain almost fully-dense parts [3]. This is due to the EBM process: the parts are printed in a vacuum environment which eliminates all impurities with high build temperatures, and thus low residual stress. In addition, EBM has faster build rates and all elements do not necessarily require any support [9]. It is renowned that fatigue properties are strictly related to surface morphology; an increase in roughness leads to a reduction of fatigue life [10; 11]. [PERSON] et al. [12] studied the influence of roughness and morphology on the fatigue life of Ti alloy components produced with different orientations, using either a laser or an EBM system. Thus, the finishing of the AM parts is an important issue; different techniques can be adopted, such as abrasive fluidized bed [2], laser treatment [13; 14; 15; 16], and chemical polishing [17; 18; 19]. Laser treatments offer some advantages compared to the other aforementioned techniques, such as absence of any mechanical contact due to the lack of tools which lead to a no wear high accuracy and high repeatability. Laser treatments are ecofriendly since they do not use any solvent or chemical agent and work with different materials, such as metals, ceramic, and polymers, just by changing the wavelength. [PERSON] et al. [15] adopted a CO\({}_{2}\) laser to polish DIN 1.2379 tool steel, achieving a roughness reduction up to 90%. [PERSON] et al. [20] used a diode laser to modify the surface of bronze sintered parts. The main results were a 70% reduction in roughness and an increase in microhardness, scratch, and wear resistance. [PERSON] et al. [21] adopted a pulsed fiber laser to polish a SKD61 steel tool, obtaining a reduction in roughness. [PERSON] et al. [22] studied the laser finishing on parts obtained by SLM. A Taguchi methodology was adopted which identified the laser power, pulse frequency, and number of repetitions as the most affecting parameters. The purpose of this work is to study the laser surface finishing of components (Ti-6 Al-4V alloy) obtained by electron beam melting (EBM) by means of a high-efficiency fiber laser operating in continuous wave. The laser energy density and scanning speed were both varied during the tests. In order to assess the quality of the treatment, either the as-built or the treated samples were analyzed by means of a 3D profilometer, digital microscopy, and scanning electron microscopy.