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Weldability study of alloys 625 and 718 fabricated by laser-based additive manufacturing
Publication . Guzman, Jhoan; Riffel, Kaue C.; Evans, William; Brizes, Eric; Avedissian, Nicholas; Farias, Francisco Werley Cipriano; Ramirez, Antonio J.; DEMI - Departamento de Engenharia Mecânica e Industrial; UNIDEMI - Unidade de Investigação e Desenvolvimento em Engenharia Mecânica e Industrial; Elsevier BV
Nickel-based alloys, Alloys 625 and 718, are widely used in the aerospace industry due to their excellent corrosion resistance and high strength at elevated temperatures. Recently, these alloys have been utilized to manufacture rocket engine components using additive manufacturing (AM) technologies such as laser powder bed fusion (LPBF) and powder-blown laser-based directed energy deposition (DED). These technologies offer faster and more cost-effective production while enabling the fabrication of near-net-shape parts that are subsequently joined by welding. However, solidification cracking susceptibility varies significantly between AM and conventionally processed materials, and limited weldability characterization has been conducted on AM-fabricated materials. This study assesses the weld solidification cracking susceptibility of Alloys 625 and 718 produced by wrought (mill-rolled), LPBF, and DED using transverse varestraint testing, Scheil-Gulliver simulations, the Crack Susceptibility Index (CSI), and the Flow Resistance Index (FRI). Transverse varestraint testing revealed that AM parts exhibited higher susceptibility due to the presence of larger and elongated grains in the fusion zone, affecting the weld solidification cracking response. In Alloy 625, the LPBF condition exhibited the highest maximum crack distance (MCD) of 2.35 ± 0.16 mm, compared to 1.56 ± 0.06 mm for wrought and 1.72 ± 0.10 mm for DED. Similarly, in Alloy 718, the DED condition showed the highest MCD of 2.93 ± 0.41 mm, while the wrought condition had an MCD of 2.01 ± 0.12 mm, and the LPBF condition reached 3.01 ± 0.33 mm at 5 % strain, without a clearly defined saturation strain. Although wrought materials demonstrated greater resistance to solidification cracking, solidification simulations did not correlate with the experimental testing, as they do not account for microstructural and mechanical factors, relying solely on chemistry.
Grain refinement of Inconel 625 during wire-based directed energy deposition additive manufacturing by in-situ added TiB2 particles
Publication . Rodrigues, Tiago A.; Malfeito, A.; Farias, Francisco Werley Cipriano; Duarte, V.; Lopes, João; Cruz Payão Filho, João da; Avila, Julian A.; Schell, N.; Santos, Telmo G.; Oliveira, J. P.; DEMI - Departamento de Engenharia Mecânica e Industrial; Faculdade de Ciências e Tecnologia (FCT); UNIDEMI - Unidade de Investigação e Desenvolvimento em Engenharia Mecânica e Industrial; DCM - Departamento de Ciência dos Materiais; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); Elsevier Science B.V., Amsterdam.
In this study, a novel method for enhancing the quality of components fabricated by wire and arc additive manufacturing (WAAM) was developed. This approach employs an innovative mechanism featuring an actuator that dispenses a solution containing refinement particles (TiB2 inoculants), in conjunction with a soldering flux that vaporizes prior to reaching the electric arc. This leaves the particles to adhere to the welding wire or be carried by the shielding gas. By implementing this device, TiB2 particles were successfully incorporated into the molten pool during the WAAM process of Inconel 625 at levels of 0.31 and 0.56 wt%. Microstructural analysis reveals a significant reduction in the size of interdendritic segregation regions when TiB2 particles are introduced. Electron backscatter diffraction analysis further reveals the transformation of columnar grains into equiaxed grains. The average grain area decreased from 1823 μm2 in the as-built sample to 583 μm2 in the sample with a TiB2 content of 0.56 wt%. In addition, an improvement in the Inconel 625 fabricated by WAAM mechanical strength was observed due to the use of TiB2 inoculants, which was primarily attributed to the effect of the grain size refinement.
Ni-based superalloy 718 fabricated by arc-based directed energy deposition
Publication . Farias, Francisco Werley Cipriano; Duarte, Valdemar Rebelo; Filho, João da Cruz Payão; Figueiredo, Arthur Ribeiro; Schell, Norbert; Maawad, Emad; Fonseca, Fabio Machado Alves da; Cormier, Jonathan; Ramirez, Antonio J.; Santos, Telmo G.; Oliveira, J. P.; DEMI - Departamento de Engenharia Mecânica e Industrial; UNIDEMI - Unidade de Investigação e Desenvolvimento em Engenharia Mecânica e Industrial; DCM - Departamento de Ciência dos Materiais; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); Elsevier
The present work describes and quantitatively assesses the strengthening mechanisms in Inconel 718 fabricated by arc-based DED (IN718 arc-based DED) through an experimentally-based approach. IN718 arc-based DED (in the as-built condition) showed a typical coarse (millimetric-sized grains) and oriented (cube texture) microstructure with a significant quantity of interdendritic eutectics (Laves and MC-type carbides). After heat treatment (1100 °C/2 h + aging), these eutectics were partially dissolved; however, the original grain size and crystallographic texture aspects were not altered. In addition, the heat treatment promoted a notorious γ′′ (Ni3Nb) and γ′ (Ni3(Al, Ti)) phases content (∼17 and 5 %, respectively), which results in superior room temperature tensile strength despite the aforementioned non-optimized microstructure. The grain size, dislocation density, precipitation content and morphology, and alloying elements in solid solution were experimentally measured and utilized as input data for a quantitative assessment of the strengthening mechanisms. This analysis concludes that the linear dependence of the majority of the strengthening mechanisms on the Taylor factor predominantly promoted the yield strength anisotropy. Furthermore, as expected, it is evidenced that the precipitation strengthening mechanism governs the final strength of IN718 arc-based DED.
Enabling electrical response through piezoelectric particle integration in AA2017-T451 aluminium parts using FSP technology
Publication . Ferreira, Pedro M.; Caçador, David; Machado, Miguel A.; Carvalho, Marta S.; Vilaça, Pedro; Sorger, Gonçalo; Farias, Francisco Werley Cipriano; Figueiredo , Arthur Ribeiro; Vidal, Catarina; DEMI - Departamento de Engenharia Mecânica e Industrial; UNIDEMI - Unidade de Investigação e Desenvolvimento em Engenharia Mecânica e Industrial; IOP Publishing
In the field of structural engineering, the integration of smart materials and structural health monitoring (SHM) has given rise to self-sensing materials (SSM), leading to a paradigm shift in SHM. This paper focuses on the interplay between self-sensing capabilities and the piezoelectric properties of lead zirconate titanate (PZT) and barium titanate (BT) in aluminium components. Leveraging Friction Stir Processing (FSP), the study explores the synthesis and performance of SSMs with embedded piezoelectric particles, potentially transforming structural engineering. The paper highlights FSP as a key methodology for incorporating piezoelectric particles into structural materials, showcasing its potential in developing SSMs with enhanced functionalities. A specific focus is placed on integrating PZT and BT particles into AA2017-T451 aluminium parts using FSP, with metallographic assessments and mechanical property evaluations conducted to analyse particle distribution and concentration. This study shows how BT and PZT particles are incorporated into AA2017-T451 aluminium to create a SSM that responds to external stimuli. Under cyclic loading, the SSMs exhibit a linear load-electrical response correlation, with sensibility increasing at lower frequencies. Metallographic analysis shows homogeneous particle distribution, while PZT induces increased brittleness and brittle fractures. Yield strength remains relatively stable, but ultimate strength decreases post-FSP. Hardness variations indicate weaker bonding with PZT particles. Eddy’scurrent testing aligns with hardness profiles, and sensorial characterization reveals a non-linear frequency-sensibility relationship, showcasing the SSMs’ suitability for low-frequency applications, particularly with PZT embedment.
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Fundação para a Ciência e a Tecnologia
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OE
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2022.13870.BD