Stainless steels play a very relevant role in the Oil, Gas and Biofuel Industry, with austenitic steel AISI 316L (ASTM A276, 2017) having significant applicability due to its great resistance to crevice and pitting corrosion, in addition to not undergoing the sensitization effect when used in high temperature services due to its low carbon content (less than 0.03%). In this context, the Additive Manufacturing processes (ISO / ASTM 52900, 2015) play an extremely important role, as they allow the manufacture of components of this alloy on demand, with the possibility of “printing” connections, flanges and other components in customized dimensions. However, the welded union between manufactured components and those manufactured in a conventional manner is still unknown. Thus, the objective of this work is to evaluate the weldability of joints between AISI 316L stainless steel pipes conventionally manufactured and by LMD (Laser Metal Deposition) Additive Manufacturing, verifying its physical integrity, according to visual inspection and mechanical properties (AWS D1.6, 2017) criteria, as well as microstructural properties through the Vickers microhardness (ASTM E384, 2016) profile of the regions of interest (ISO 6507-1, 2019). For the execution of this work, 2 ½”nominal diameter and 5.16 mm thick pipes were used, joined at V groove butt joint (37.5º bevel) in one of the working cells of the Laprosolda Group, composed of anthropomorphic robot of six degrees of freedom interfaced with multiprocessor source operating in constant voltage mode (Conventional GMAW). One of the pipes was manufactured in a conventional manner (seamed), while the other was obtained via LMD (Laser Metal Deposition) Additive Manufacturing. The consumables used were: filler material ER316L, with nominal diameter of 1.20 mm; shielding gas Ar+2%O2 at 14 l/min and pure Argon at 2 l/min as a purge gas. The welding process was configured to operate with a setting voltage of 13.5 V, wire feed speed of 3.1 m/min, 50% inductance and 15 mm contact tip to work distance. The weld beads were made with torch movement (orbital) in downhill progression, together with transverse oscillation (amplitude of 2.25 mm and frequency of 1.4 Hz). Current and voltage electrical signals were monitored with a resolution of 14 bits and a sample rate of 5 kHz. After the process of joining the pipes, performed in a single pass, the joints were analyzed visually and, after attesting the absence of discontinuities and dimensional sanity (AWS D1.6, 2017), cuts were made across the direction of the joint in the positions flat (15º), vertical descending (90º) and overhead (165º) for macrographies, in such a way to verify the internal presence of defects. The visual inspection of the weld beads, carried out both internally and externally to the pipes, did not indicate the presence of lack of fusion, overlap or lack of penetration of the root, whereas the macrographs also did not indicate any defects, such as lack of fusion and solidification cracks. Based on the results presented, it is possible to affirm that it was successful in the welded joint between AISI 316L stainless steel pipes manufactured in a conventional way and by LMD Additive Manufacturing (Laser Metal Deposition), since the welding process was carried out regularly and with little spatter generation, where both visual inspection and macrographs did not point out defects in the weld bead in the flat, vertical and overhead positions.
Keyword: LMD; Additive Manufacturing; GMA Welding; Weldability.