MM Science Journal | www.mmscience.eu ISSN 1803-1269 (Print) | ISSN 1805-0476 (On-line) Special Issue | HSM 2019 15 th International Conference on High Speed Machining October 8-9, 2019, Prague, Czech Republic DOI: 10.17973/MMSJ.2019_11_2019079 MM Science Journal | 2019 | Special Issue on HSM2019 3258 HSM2019-101 FINISH MILLING STUDY OF Ti-6Al-4V PRODUCED BY LASER METAL DEPOSITION (LMD) A. Kallel 1,2 *, A. Duchosal 1 , G. Altmeyer 1 , A. Morandeau 2 , H. Hamdi 3 , R. Leroy 1 , S. Méo 1 1 Univ Tours, Univ Orléans, INSA CVL, LaMé, 7, Avenue Marcel Dassault 37200 Tours, France 2 Sandvik Tooling France - Division Coromant, Rue Henri Garih, 37230 Fondettes, France 3 Univ Lyon, ENISE, LTDS, 58 Rue Jean Parot, 42100 Saint Etienne, France *Corresponding author; e-mail: achref.kallel@sandvik.com Abstract Components produced and repaired by the Laser Metal Deposition (LMD) process require finish- machining steps in order to improve the poor geometrical tolerance of the functional surfaces. In this work, the LMD process was conducted to build up samples from Ti-6Al-4V powders. The effect of the face milling process on surface roughness of the Ti-6Al-4V parts was studied in different build directions. The effect of the heat treatment was also considered. Changes in roughness and micro-hardness were evaluated and compared in each condition. Cutting forces were also measured in order to evaluate loading characteristic on the cutting insert. The heat-treated sample shows lower cutting forces in comparison with the as-build material. Different values of the surface roughness of the machined parts were obtained as a consequence of the microstructure variation. Keywords: Laser Metal Deposition (LMD); Milling; Ti-6Al-4V; Heat treatment; Surface integrity 1 INTRODUCTION Laser Metal Deposition (LMD) is a well-employed additive manufacturing (AM) process to build complex near net- shape and repair high-value parts. The process was first commercialized as Laser Engineered Net Shaping (LENS TM ) and developed by Sandia National Laboratory in 1993 [Atwood 1998]. The process gained more industrial interests thanks to its ability to produce massive components, high build rates, low porosity and competitive properties compared to the conventional material [Bi 2006]. Furthermore, the LMD process showed high capabilities of mixing multiple materials and repairing high value components [Hedges 2006]. This process is also able to build materials with high melting temperature, such as nickel-based and titanium alloys. A special care needs to be addressed when producing components with qualification and certification requirements. Indeed, the produced parts by AM commonly require at least one post-processing [Blackmore 2010][Tian 2014] and surface finish operation [Formanoir 2016] to enhance the material properties and to satisfy the quality and tolerance of the surface. During the building process, Ti-6Al-4V parts undergo severe inhomogeneous cooling rates and cycles. This can lead to a difference in the microstructure and subsequently, in mechanical properties. Variation in the material properties and high anisotropy could appear even when similar building parameters are used [Zhao 2017]. Therefore, the machinability of the produced parts is expected to vary throughout the deposited structure. Producing ready-to-use additive parts without the need of the post processing remains a big challenge for the AM machine makers and users alike [Kianian 2018]. The additive parts are characterized by oxidized and unmelted particles, a staircase morphology, pores and lack of fusion [Li 2003]. This could affect material properties and the surface of the components. A way to improve the material properties and to reduce material defects is to realize a Hot Isostatic Pressing (HIP) treatment [Thijs 2010]. A surface finish step is also required to fulfil the requirements of the functional surfaces especially when dimensional accuracy is expected. Hybrid machines are then developed allowing to merge AM and machining capabilities. These machines are capable of combining additive and subtractive processes of a metallic part within the same enclosure [Flynn 2016]. The interest of studying the machinability of the AM components is motivated by the development of new AM materials and applications and the need to understand the effect of post processing on the cutting operation. Nevertheless, the machining process of AM parts is less studied compared to the conventional ones. The term machinability could be defined as the ease or the difficulty of a material to be machined. The most used criteria to evaluate the machinability are the tool life, wear mechanism, cutting forces, surface integrity, cutting temperature and chip formation [Mills 1983]. The Ti-6Al-4V is one of the most investigated alloy in additive manufacturing domain due to its well compatibility with the majority of the AM processes and its large use in critical applications such as medical and aeronautical