Francisco Briones

This study evaluates oscillating fiber laser welding as an alternative to gas metal arc welding with an active shielding gas (GMAW/MAG) for manufacturing 4.25 mm thick SAE 1010 agricultural wheel rims. A systematic product development approach guided technology selection. The comparison included process energy, weld geometry, microstructure, grain size, Vickers microhardness, guided-bend testing, and industrial forming. Estimated GMAW/MAG heat input was 0.64 kJ/mm, whereas nominal incident laser energy was 0.019 kJ/mm; these quantities do not represent equivalent measurements of absorbed heat. Measurements from one transverse cross-section per welding condition showed a smaller weld-face width (5.70 vs. 12.97 mm), lower convexity (0.56 versus 3.93 mm), and a narrower heat-affected zone (0.85 versus 2.10 mm) for laser welding compared with GMAW/MAG. Less grain coarsening was observed in the laser-welded heat-affected zone. Mean fusion-zone hardness was 158.6 ± 18.9 HV1 for laser welding and 190.4 ± 11.0 HV1 for GMAW/MAG. Both conditions passed the guided-bend tests. All ten laser-welded specimens completed industrial forming, whereas two of ten GMAW/MAG specimens fractured during cone opening. The examined laser-welded cross-section exhibited a narrower weld profile than the examined GMAW/MAG cross-section. The laser-welding manufacturing route also eliminated the post-weld grinding operation under the investigated conditions.

This study evaluates the effect of printing orientation on the wear resistance of 3D-printed nylon fabricated via Fused Deposition Modeling (FDM). We conducted abrasive wear resistance tests, thermal analysis, and microstructural characterization using scanning electron microscopy before and after wear testing. The results show that alternating printing directions lead to significantly higher wear. Under a normal load of 130 N, this configuration caused the exposure of up to four layers. At the same time, single-orientation prints exhibit lower material loss and better filament cohesion. DSC analysis reveals that all printed samples, regardless of wear exposure, display dual melting temperatures (T_s1 and T_s2) due to distinct crystalline phase formations. Abrasion decreases the secondary melting temperature (T_s2) and increases enthalpy by up to 144% compared to unprinted nylon, highlighting the thermal history on structural properties. These findings emphasize the critical role of printing configurations in optimizing the tribological performance of 3D-printed nylon for industrial applications.

This study evaluates the wear and corrosion resistance of the Cu-50Ni-5Al alloy reinforced with CeO2 nanoparticles for potential use as anodes in molten carbonate fuel cells (MCFCs). Cu–50Ni–5Al alloys were synthesized, with and without the incorporation of 1% CeO2 nanoparticles, by the mechanical alloying method and spark plasma sintering (SPS). The samples were evaluated using a single scratch test with a cone-spherical diamond indenter under progressive normal loading conditions. A non-contact 3D surface profiler characterized the scratched surfaces to support the analysis. Progressive loading tests indicated a reduction of up to 50% in COF with 1% NPs, with specific values drop-ping from 0.48 in the unreinforced alloy to 0.25 in the CeO2-doped composite at 15 N of applied load. Furthermore, the introduction of CeO2 decreased scratch depths by 25%, indicating enhanced wear resistance. The electrochemical behavior of the samples was evaluated by electrochemical impedance spectroscopy (EIS) in a molten carbonate medium under a H2/N2 atmosphere at 550 °C for 120 h. Subsequently, the corrosion products were characterized using X-ray diffraction (XRD), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS), and X-ray photoelectron spectroscopy (XPS). The results demonstrated that the CeO2-reinforced alloy exhibits superior electro-chemical stability in molten carbonate environments (Li2CO3-K2CO3) under an H2/N2 atmosphere at 550 °C for 120 h. A marked reduction in polarization resistance and a pronounced re-passivation effect were observed, suggesting enhanced anodic protection. This effect is attributed to the formation of aluminum and copper oxides in both compositions, together with the appearance of NiO as the predominant phase in the materials reinforced with nanoparticles in a hydrogen-reducing atmosphere. The addition of CeO2 nanoparticles significantly improves wear resistance and corrosion performance. Recognizing this effect is vital for creating strategies to enhance the material’s durability in challenging environments like MCFC.

This work presents the effect of CeO₂ nanoparticles (CeO₂–NPs) on Cu–50Ni–5Al alloys on morphological, microstructural, degradation, and electrochemical behavior at high temperatures. The samples obtained by mechanical alloying and spark plasma sintering were exposed to a molten eutectic mixture of Li₂CO₃–K₂CO₃ for 504 h. The degradation of the materials was analyzed using gravimetry measurements and electrochemical impedance spectroscopy. Different characterization techniques, such as X-ray diffraction and scanning electron microscopy, were used to investigate the phase composition, parameter lattice, and microstructure of Cu–Ni–Al alloys reinforced with CeO₂–NPs. The hardness of the composite was also examined using the Vickers hardness test. Gravimetry measurements revealed that the sample with 1 wt.% CeO₂–NPs presented the best response to degradation with a less drastic mass variation. Impedance analysis also revealed that by adding 1 wt.% CeO₂–NPs, the impedance modulus increased, which is related to a lower porosity of the oxide film or a thicker oxide layer. The microhardness also significantly increased, incorporating 1 wt.% CeO₂–NPs, which reduced with higher CeO₂–NPs content, which is possibly associated with a more uniform distribution using 1 wt.% CeO₂–NPs in the Cu–Ni–Al matrix that avoided the aggregation phenomenon.

The composition of the filler electrodes, as well as the shielding gases, has a strong impact on the static and dynamic properties of welded joints in HSLA steels. The content of Cr, Ni, and Mo, along with the shielding gases, helps maintain the hardness values in the HAZ of HSLA steels welded using the GMAW process, resulting in a positive impact on the fatigue life of the joints. Maintaining fatigue properties in the regions of the heat-affected zone is crucial. The increase in the size of the HAZ, coupled with microstructural changes, leads to a reduction in the hardness values in this region, contributing to a decrease in the fatigue life of welded joints. In this study, the effects of using different filler electrodes and shielding gases on the fatigue properties of welded joints in LNE 600 steel with a thickness of 4.75 mm, welded using the GMAW process, were evaluated. It was possible to observe a reduction in the hardness values in the HAZ region and a similar static resistance behavior for all evaluated conditions, except for the ER70S-6 electrode with 5% O₂ gas, where the fatigue life showed better results with the application of the ER120S-G electrode.

Resistance to atmospheric corrosion in different environments located in Chile and the corrosion’s effect on the mechanical properties of SAE 1020 steel were studied. Atmospheric corrosivity categories at each station under study were determined. These categories were C2, for Laja; C3 and C4, for the Arica and Antarctic stations, respectively; and the most aggressive, C5 and higher at Quintero. These specific environments significantly influenced the mechanical responses of steel exposed for 36 months. Rupture elongation, the modulus of toughness, ultimate tensile strength, and hardness of the material all decreased as a function of environmental atmospheric aggressiveness. Lowered ductility is the result of the increased corrosion rate due to the high deposition of chlorides. This is due to the morphology of material degradation, which consequently occurs as pores, microstrains, and other defects that promote early rupture of the steel.