| Abstract Scope |
In the face of the growing need of industries, the Wire Arc Additive Manufacturing (WAAM) plays an important role, enabling the construction and repair of parts in an agile and economical way, aiming to meet specific demands, especially in the Oil and Gas, Naval and Aerospace sectors. In this context, the Direct Energy Deposition processes, especially the GMA-DED (or WAAM), have been consolidating themselves as a solution to these demands, since, among the processes of additive manufacturing in metals, it is one of the ones with greater economic viability and production capacity, both in volume of construction and in rate and speed of deposition, for pieces of low or medium geometric complexity. When it comes to parts made of steel, there is a wide range of consumables aimed at meeting the needs of the welding market, but still little or not applied in additive manufacturing. Thus, in order to meet the design requirements, it is necessary to know the mechanical properties of the deposited metal, which differ from the mechanical properties found in the weld metal. This is due to several aspects, but especially those related to the deposition conditions and the process variables used. Therefore, we sought to build parts using commercial wire-electrodes, commonly used in welding, in order to evaluate the mechanical properties of the deposited metal when used in additive manufacturing by using a developed deposition cell in the Laprosolda/UFU Research Group. This cell is composed of an anthropomorphic robot with six degrees of freedom interfaced with a multi-process source operating in constant current mode and a pulsed MAG process. As deposition material, carbon steel and microalloyed wires were used (AWS ER70S-6, ER80S-G, ER80S-B2, ER110S-1 and ISO 14341-G 4Si1), with 1.2 mm diameter and Ar+2%O2 at 18 L/min as shielding gas. Pulsed MAG process was adjusted so that the mean current was equal to 150 A during the entire deposition of a rectangular piece with programmed dimensions of 285x180x30 mm. After the manufacture of the pieces, initially, a visual and dimensional analysis was performed, followed by Phased Array Ultrasound inspection. After verifying the absence of discontinuities, tensile tests (ASTM E8M, 2016), Charpy Impact tests at -30șC (ASTM E23, 2016) and bending tests (AWS D1.1, 2015) were performed, in such a way as to measure properties in two perpendicular directions (horizontal and vertical) and evaluate possible anisotropy. The average total deposition time was 4h15min uninterrupted, with a total deposited mass of 12.2 kg, that is, the deposition rate was 2.87 kg/h. The Visual, Dimensional and Phased Array Ultrasound Non-destructive Tests (NDT) did not indicate the presence of any discontinuity. Through the analysis of the stress-strain curves, the materials showed ductile behavior with high elongation (42 ± 6%) and good mechanical resistance: 354 ± 14 MPa yield strength and 491 ± 17 MPa strength limit, in the case of carbon steel. Another point to highlight is the isotropy of the part, in which it is not possible to identify differences in properties between the specimens removed horizontally or vertically. Regarding the Charpy Impact Test, it was possible to confirm that the high tenacity with the absorbed energy reaching 271 ± 40 J @ -30șC. In general, the deposited materials showed isotropic behavior in terms of yield and tensile strengths, as well as in total elongation, with the exception of G4Si, which showed greater elongations in the specimens taken in the longitudinal direction of deposition. It was also found that, with some exceptions, the deposited material proved to be more malleable and less resistant than the standardized values. Furthermore, it can be noted that the average deposition current has a significant influence on the properties and mechanical behavior of the materials involved in this work. Keywords: GMA-DED; WAAM; Pulsed transfer. |