Browsing by Author "Rodrigues Pardal, Gonçalo"
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Item Open Access Additive techniques to refurbish Ni based components(Associação Brasileira de Soldagem, 2019-05-09) Cardozo, Eloisa Pereira; Rodrigues Pardal, Gonçalo; Ríos, Sergio; Ganguly, Supriyo; D’Oliveira, Ana Sofia C. M.The attractiveness of additive techniques to refurbish worn components requires the availability of data from different process. This study correlates two additive techniques, Plasma Transferred Arc (PTA – AM) and Direct Laser Deposition (DLD), using IN 625 wire. Specific features of each technique are discussed regarding their potential use to recover geometry and properties of worn components. Multilayers were processed with each technique on a section of a blade and the interaction between materials together with the effect of post deposition heat treatment were characterized. Results show that there are differences in the final microstructure and in the interaction with the part being refurbished imposed by the additive technique used. Competitive changes can be made by changing the feedstock. PTA-AM using powder material exhibits a microstructure that approaches that obtained in DLD using wire.Item Open Access Application of laser in seam welding of dissimilar steel to aluminium joints for thick structural components(Elsevier, 2015-04-01) Martins Meco, Sonia Andreia; Rodrigues Pardal, Gonçalo; Ganguly, Supriyo; Williams, Stewart W.; McPherson, NormanLaser welding-brazing technique, using a continuous wave (CW) fibre laser with 8000 W of maximum power, was applied in conduction mode to join 2 mm thick steel (XF350) to 6 mm thick aluminium (AA5083-H22), in a lap joint configuration with steel on the top. The steel surface was irradiated by the laser and the heat was conducted through the steel plate to the steel-aluminium interface, where the aluminium melts and wets the steel surface. The welded samples were defect free and the weld micrographs revealed presence of a brittle intermetallic compounds (IMC) layer resulting from reaction of Fe and Al atoms. Energy Dispersive Spectroscopy (EDS) analysis indicated the stoichiometry of the IMC as Fe2Al5 and FeAl3, the former with maximum microhardness measured of 1145 HV 0.025/10. The IMC layer thickness varied between 4 to 21 μm depending upon the laser processing parameters. The IMC layer showed an exponential growth pattern with the applied specific point energy (Esp) at a constant power density (PD). Higher PD values accelerate the IMC layer growth. The mechanical shear strength showed a narrow band of variation in all the samples (with the maximum value registered at 31.3 kN), with a marginal increase in the applied Esp. This could be explained by the fact that increasing the Esp results into an increase in the wetting and thereby the bonded area in the steel-aluminium interface.