Wire-arc additive manufacturing of a duplex stainless steel: thermal cycle analysis and microstructure characterization

Abstract

The evolution of microstructures with thermal cycles was studied for wire-arc additive manufacturing of duplex stainless steel blocks. To produce samples, arc energy of 0.5 kJ/mm and interlayer temperature of 150°C were used as low heat input-low interlayer temperature (LHLT) and arc energy of 0.8 kJ/mm and interlayer temperature of 250°C as high heat input-high interlayer temperature (HHHT). Thermal cycles were recorded with different thermocouples attached to the substrate as well as the built layers. The microstructure was analyzed using optical and scanning electron microscopy. The results showed that a similar geometry was produced with 14 layers-4 beads in each layer-for LHLT and 15 layers-3 beads in each layer-for HHHT. Although the number of reheating cycles was higher for LHLT, each layer was reheated for a shorter time at temperatures above 600°C, compared with HHHT. A higher austenite fraction (+ 8%) was achieved for as-deposited LHLT beads, which experienced faster cooling between 1200 and 800°C. The austenite fraction of the bulk of additively manufactured samples, reheated several times, was quite similar for LHLT and HHHT samples. A higher fraction of secondary phases was found in the HHHT sample due to longer reheating at a high temperature. In conclusion, an acceptable austenite fraction with a low fraction of secondary phases was obtained in the bulk of wire-arc additively manufactured duplex stainless steel samples (35-60%), where higher austenite fractions formed with a larger number of reheating cycles as well as longer reheating at high peak temperatures (800-1200°C).

GMAW Cold Wire Technology for Adjusting the Ferrite–Austenite Ratio of Wire and Arc Additive Manufactured Duplex Stainless Steel Components

“…Investigations on the effects of the thermal cycles in WAAM using the filler metal G 22 9 3 were recently carried out by Hosseini et al [19]. Depending on the heat input and the reheating during welding of the subsequent layers, ferrite contents between 40-65% were detected.…”

Wire Arc Additive Manufacturing of Stainless Steels: A Review

“…Other factors, such as deposition path and wire material, also affect the surface condition. During wire-arc additive manufacturing of duplex stainless steel blocks, an alternating direction path generated the uniform layer height, while a one-direction deposition path yielded uneven sides due to the heat accumulation at the stop point during the deposition of each layer [101]. Rodriguez et al [88] applied multi-bead CMT deposition parameters to build 316L stainless steel walls.…”

“…Common defects and their formation reasons in WAAM metallic parts are listed in Table 8. Porosity [116], cracks, and lack of fusion [101] are the typical defects found in stainless steel parts produced by WAAM. Process parameters, such as deposition paths and heat input, cause defects during deposition.…”

“…Compared to GTAW-and PAW-based WAAM, GMAW have more problems of excessive heating, spattering, or porosity, because the electric current acts directly on the feedstock [88]. Some porosities and lack of fusion appears on the cross section of GMAW duplex stainless steel samples, especially between the beads, as shown in Figure 11 [101]. Gordon et al [116] investigated porosity data for three different locations in the WAAM stainless steel 304 build.…”

The Effect of Microstructural Imperfections on Corrosion Fatigue of Additively Manufactured ER70S-6 Alloy Produced by Wire Arc Deposition

“…Additive manufacturing (AM), processes are principally divided into three main categories: powder-bed technology (PBT), inkjet printing and blown powder/wire technology. Currently, the most popular process is PBT, which is practically implemented by means of selective laser melting (SLM) and electron beam melting (EBM) [1][2][3][4][5]. The wire arc additive manufacturing (WAAM) process is carried out using an electric arc as the energy source and consumable wires as the filler material for layer-by-layer metal deposition controlled by 3D CAD software, under an inert gas atmosphere [6,7].…”