Abstract

: Current additive manufacturing (AM) processes are mainly focused on powder bed technologies, such as electron beam melting (EBM) and selective laser melting (SLM). However, the main disadvantages of such techniques are related to the high cost of metal powder, the degree of energy consumption, and the sizes of the components, that are limited by the size of the printing cell. The aim of the present study was to evaluate the environmental behavior of low carbon steel (ER70S-6) produced by a relatively inexpensive AM process using wire feed arc welding. The mechanical properties were examined by tension testing and hardness measurements, while microstructure was assessed by scanning electron microscopy and X-ray diffraction analysis. General corrosion performance was evaluated by salt spray testing, immersion testing, potentiodynamic polarization analysis, and electrochemical impedance spectroscopy. Stress corrosion performance was characterized in terms of slow strain rate testing (SSRT). All corrosion tests were carried out in 3.5% NaCl solution at room temperature. The results indicated that the general corrosion resistance of wire arc additive manufacturing (WAAM) samples were quite similar to those of the counterpart ST-37 steel and the stress corrosion resistance of both alloys was adequate. Altogether, it was clearly evident that the WAAM process did not encounter any deterioration in corrosion performance compared to its conventional wrought alloy counterpart.

Highlights

  • The growing interest in additive manufacturing (AM) technology in the last decade has been largely due to the inherent advantages of this technology in terms of creating highly complex geometries in a relatively short time [1,2,3,4,5,6]

  • The results indicated that the general corrosion resistance of wire arc additive manufacturing (WAAM) samples were quite similar to those of the counterpart ST-37 steel and the stress corrosion resistance of both alloys was adequate

  • The WAAM test samples were machined from hollow cylindrical parts that were built to a height of 120 mm, a mid-wall radius of 55 mm and 15 mm wall thickness as shown in Figure 1, using 1.2 mm of ER70S-6 wire [16]

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Summary

Introduction

The growing interest in additive manufacturing (AM) technology in the last decade has been largely due to the inherent advantages of this technology in terms of creating highly complex geometries in a relatively short time [1,2,3,4,5,6]. Most relevant production and research activities focus on 3D printing processes using powder bed technology (PBT), such as selective laser melting (SLM). The deposition rate of the PBT process is relatively low due to a very thin printing layer (30–60 μm) and the low scan speed of the energy source (SLM or EBM) [8]. The inherent limitations of the PBT process highlight the potential of wire arc additive manufacturing (WAAM) as an attractive alternative technology. In this process, a metal wire serves as raw material, with relatively reduced energy consumption being required to fuse the wire into a pre-designed metal component. The WAAM process usually uses widely used welding technologies, Metals 2019, 9, 888; doi:10.3390/met9080888 www.mdpi.com/journal/metals

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