This research activity deals with 3D printing composites fabricated by Continuous Fiber/Filament Fabrication with an innovative thermoplastic matrix infilled with microcarbon fiber, i.e., Onyx, and ...carbon reinforcement. Three groups of additively manufactured samples were printed and tested to evaluate the possibility of avoiding the drilling phase to increase the bearing resistance and evaluate the parts' properties: standard geometry, post-process drilling, and customized geometry. Different configurations were realized for the additively manufactured and drilled samples to assess the reinforcement effect on the bearing performance and identify the 3D printing technology limits. Finally, the customized sample represents a new approach to conceiving a better solution for enhancing the bearing strength. Pin-bearing stress and stiffness have been analyzed through experimental methods, the material compaction quality was detected by ultrasound technique, and failure modes have been discussed. Concerning the additive samples, the bearing strength decreased in all reinforced printed configurations due to the technological limitations of the CFF process. However, exploiting a more flexible approach in the design, a novel bearing configuration with a custom infill strategy was proposed, reaching high values of bearing strength and stiffness. This resulted in a reduction in costs and weight, taking one step toward more sustainable production.
Chromium carbides are widely used as functional coatings on steel structures in high-end applications, from energy to marine and aerospace sectors thanks to their corrosion and wear resistance at ...elevated temperatures. In the present work, a low-power compact plasma spray (CPS) equipment was used to deposit Cr3C2-based cermet coatings on carbon steel substrate. Design of experiment was applied to select and optimize the spraying parameters, namely current, stand-off distance, scanning speed, plasma gas rate and powder feeding rate. ANOVA analysis was conducted to estimate the effect of the spraying variables on morphology and mechanical properties of the coatings and evaluate the optimal spraying condition. Dense and compact coatings were fabricated by using the CPS. By optimizing the processing parameters, coating hardness equal to approximately 600 HV and average thickness ranging around 600 μm were obtained, while the adhesion strength was approximately equal to 14 MPa. Intermediate phases of Cr carbides were produced by the dissolution of the primary Cr3C2 induced by melting and re-solidification of the particles. The presence of weaker carbide phase, inter-lamellae different features and porosity also caused the scattered hardness values observed in the coatings.
•Low power compact plasma spray technique demonstrated to produce sound chromium carbide-based cermet coatings.•The properties of the Cr3C2-NiCr coating are mainly influenced by current, stand-off distance and plasma flow rate.•Coating adherence and hardness obtained under optimal configuration meet the requirements for applications in CSP plants.•The inflight dissolution of Cr3C2 and the related porosity led to a decrease in the mechanical properties of the coatings.
This study investigates the potential of Fluidized Bed Finishing (FBF) of square flat AlSi10Mg specimens manufactured via Laser-Powder Bed Fusion (L-PBF) additive manufacturing technology. Two FBF ...operational modes were experimentally investigated: I) with stationary specimens; II) with specimens under controlled rotational motion. Four different abrasive materials have been tested, quartz sand, corundum, irregular steel and cut wire steel particles, characterized by different hardness, density and shape. The effect of the abrasive material, processing time and specimen tilt angle was investigated. Results showed moderate smoothing under stationary specimen configuration, while good finishing for rotation-assisted tests, maximum reduction of the surface roughness of 12% and 67%, respectively. Steel particles were the most effective bed material, with particle density overtaking hardness as key particle property. The optimal tilt angle was the one that maximized sliding and shear. Altogether, surface finishing is driven by surface shear forces dominated by inertial stresses in particulate phase.
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•Fluidized Bed Finishing (FBF) of specimens made by additive manufacturing is investigated.•Rotation-assisted FBF is more efficient than stationary FBF.•Particle density is the key to the abrasive potential of powders in FBF conditions.•Plain shear flow of abrasives close to the specimen maximizes the surface finishing.•The finishing mechanism is associated with particle removal and plastic deformation.
Aluminum has become increasingly important in the automotive sector due to its ability to reduce vehicle weight without compromising structural performance. However, joining different types of ...aluminum alloys can be challenging due to their different thermal and mechanical characteristics. Concurrently, friction stir processing (FSP) is a material processing technique that has garnered considerable attention for its versatility and industrial applicability, and it may represent a preliminary phase to correctly perform friction stir welding, which is a welding technology used to join different types of aluminum alloys. In this context, this study presents an extensive experimental campaign of FSP performed on 5754-H111 and 6082-T6 alloys, varying two rolling directions and four welding speeds. The processed materials were characterized, including cupping and tensile tests, microstructure analysis, and a correlation between welding parameters, microstructure, and mechanical resistance. In addition, a numerical method was proposed to simulate the Erichsen tests and predict the formability of the materials, before and after the FSP processes. The results showed that both alloys exhibited good formability after the FSP process, but with different behavior. AA6082 underwent internal decohesion and dynamic recrystallization, resulting in the absence of defects and an increase in ductility and cold formability. AA5754 experiences more difficulty with material flow during FSP and showed the presence of tunnel defects in all analyzed process conditions. However, the alloy 5754 did not undergo softening and had comparable mechanical behavior and cold formability to the base material. These results were validated by the numerical method proposed.
This work deals with the investigation and characterization of Ti6Al4V parts produced with an intriguing manufacturing process belonging to the Wire Arc Additive Manufacturing (WAAM) family: the Cold ...Metal Transfer technology (CMT). Wall‐shaped parts were produced according to different process parameters, namely the wire feed speed and voltage–current combinations, leading to different energy inputs. The parts were characterized in terms of surface morphology, microhardness, microstructure, tensile properties, and fatigue crack growth. The results suggested that the investigated deposition parameters led to similar results. Moreover, the mechanical and fatigue crack growth behavior was in line with parts of the same alloy produced through other manufacturing routes, whereas the microstructure type was the result of the fast cooling of the molten material. Finally, considering the simple system adopted to avoid oxidation during the deposition stage, the results suggested that CMT is a promising manufacturing technique for titanium alloy semifinished parts.
Highlights
Wall‐like parts made of Ti6Al4V alloy were produced through WAAM‐CMT technology
Sound parts with minimum oxidation were produced through a simple enveloping system
The parts had properties similar to those of more traditional manufacturing routes
The microstructure, tensile, and fatigue crack growth behavior were quite isotropic
•Influence of process parameters under constant energy input on microstructure and microhardness was elucidated.•Influence of processing conditions on top surface roughness was discussed.•The link ...between process parameters and properties was studied considering the interaction between beam and material.•Guidelines to choose the process parameters were released.
The role of the process parameters under a fixed energy density in Electron Beam Melting of Ti6Al4V was investigated. The beam current, scan speed and line offset were varied in a wide range keeping constant the energy density achieved, aiming to highlight the influence of each parameter on the properties of the printed parts. Microstructure, microhardness and top surface roughness were chosen as measured output. The results obtained showed that the amount of energy adsorbed by the metal is depending on beam current and scan speed, this due to the complex interaction between the electrons of the beam and the atoms of the material. As a consequence, the samples showed different properties, even if the adopted energy density was the same, the influence of the process parameters on the above-mentioned measured output was assessed.
This paper deals with the dissimilar friction stir lap welding of AA2198 and AA6082 thin sheets. The influence of processing parameters, namely welding speed and tool rotational speed on joint ...features, microstructure, and mechanical properties were investigated by implementing a full factorial design of experiments. During the welding process, axial and transversal forces were continuously measured using a dedicated fixture equipped with sensors aiming at the correlation of this processing parameter with the quality of the achieved joints. The microstructural analysis provided a detailed view of the metallurgical features such as hook, and its relative influence exhibited on the welded joints. Microhardness distribution and lap shear behavior were assessed and correlated with the metallurgical analysis.
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