Journal of Manufacturing Processes 59 (2020) 739–749 Available online 20 October 2020 1526-6125/© 2020 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights reserved. Effect of milling parameters on HSLA steel parts produced by Wire and Arc Additive Manufacturing (WAAM) J.G. Lopes, Carla M. Machado, Valdemar R. Duarte, Tiago A. Rodrigues, Telmo G. Santos, J. P. Oliveira * UNIDEMI, Department of Mechanical and Industrial Engineering, NOVA School of Science and Technology, Universidade NOVA de Lisboa, 2829-516, Caparica, Portugal A R T I C L E INFO Keywords: HSLA steel Slot milling WAAM Build-up edge ABSTRACT Additive manufacturing is considered a motivator for the development of the industrial world. Recent advances show that Wire and Arc Additive Manufacturing (WAAM) has the potential to become a relevant method for the fabrication of large complex-shaped metallic components. In this study, we address one of the most important post-processing methods for WAAM parts to be used in structural applications, milling. In this work, thin-walled high strength low alloy steel parts were manufactured by WAAM and their micro- structure was characterized. Then, a milling strategy which considered the microstructure and local mechanical properties of each part was employed. The results show that the mechanical behavior of the as-built parts does not yield a signifcant infuence on the milling process. Overall, it was ascertained that the quality of the milled surfaces improves, that is, has lower roughness, with the increase of cutting speed and with the decrease of feed per tooth. Nevertheless, we highlight the need for more attention to be dedicated on post-process machining operations after WAAM, to establish the best strategies aiming at decreasing tool wear, while maintaining both high surface quality and production rates. 1. Introduction Based on the concept of creating an object in a layer by layer fashion, additive manufacturing (AM) has experienced an increase in industry attention over the past decades. In fact, the versatility and cost-effcient approach to produce complex-shaped components makes AM processes the core of a new industrial era, based on the wide the range of materials that can be processed by these technologies. Currently, the most common methods for this manufacturing approach are Powder Bed Fusion (PBF) and Directed Energy Deposition (DED). According to the ISO/ASTM 52,900:2015 standard [1], PBF is categorized by a thermal energy that is selectively used to fuse various regions of a powder bed. Whereas DED processes are characterized by the simultaneous fusion and deposition of the feedstock material. A further classifcation is based on the primary heat source such as: laser, electron beam or plasma and arc, as well as the type of feedstock ma- terial in use: wire or powder. As a directed energy deposition process, Wire and Arc Additive Manufacturing (WAAM) is a popular AM technique that allows for the rapid manufacturing of large metallic parts with a high deposition rate and low equipment cost granting it to be considered as an environ- mentally friendly approach for manufacturing. The ability to use wire as the feedstock material increases the effciency of the process when compared to powder-based techniques by avoiding the necessity for constrained build volumes and powder recycling. Despite the advantages that WAAM exhibits as a metallic additive manufacturing method, the process displays some challenges that must be addressed. As established in literature [2–4], the main defects of WAAM deposited parts are poor surface quality, porosity, distortion, residual stresses and cracking. In steels, the most problematic defect in terms of dimensional accuracy and surface requirements is the typical waviness. However, to address some of these concerns, Xiong et al. [5] presented a study on the impact of WAAM process parameters on the fnal waviness exhibited in thin-walled structures. A notable outcome of this work is that proper parameter optimization can signifcantly reduce the waviness of the as-built parts, with obvious advantages in material savings. Nevertheless, the waviness is an intrinsic characteristic of WAAM, thus requiring other subtractive approaches to deal with it. As * Corresponding author. E-mail address: jp.oliveira@fct.unl.pt (J.P. Oliveira). Contents lists available at ScienceDirect Journal of Manufacturing Processes journal homepage: www.elsevier.com/locate/manpro https://doi.org/10.1016/j.jmapro.2020.10.007 Received 16 March 2020; Received in revised form 7 July 2020; Accepted 2 October 2020