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Abstract:The attractiveness of additive manufacturing (AM) relates to the ability of this technology to rapidly produce very complex components at affordable costs. However, the properties and corrosion behavior, in particular, of products produced by AM technology should at least match the properties obtained by conventional technologies. The present study aims at evaluating the corrosion behavior and corrosion fatigue endurance of AlSi10Mg alloy produced by selective laser melting (SLM) in comparison with its conventional counterpart, gravity cast alloy. The results obtained indicate that the corrosion resistance of the printed and cast alloys was relatively similar, with a minor advantage to the printed alloy. The corrosion fatigue endurance of the printed alloy was relatively improved compared to the cast alloy. This was mainly attributed to the significant differences between the microstructure and defect characteristics of those two alloys.

Three-dimensional (3D) printing technologies have become an attractive manufacturing process to fabricate scaffolds in tissue engineering. Recent research has focused on the fabrication of alginate complex shaped structures that closely mimic biological organs or tissues. Alginates can be effectively manufactured into porous three-dimensional networks for tissue engineering applications. However, the structure, mechanical properties, and shape fidelity of 3D-printed alginate hydrogels used for preparing tissue-engineered scaffolds is difficult to control. In this work, the use of alginate/gelatin hydrogels reinforced with TiO2 and β-tricalcium phosphate was studied to tailor the mechanical properties of 3D-printed hydrogels. The hydrogels reinforced with TiO2 and β-TCP showed enhanced mechanical properties up to 20 MPa of elastic modulus. Furthermore, the pores of the crosslinked printed structures were measured with an average pore size of 200 μm. Additionally, it was found that as more layers of the design were printed, there was an increase of the line width of the bottom layers due to its viscous deformation. Shrinkage of the design when the hydrogel is crosslinked and freeze dried was also measured and found to be up to 27% from the printed design. Overall, the proposed approach enabled fabrication of 3D-printed alginate scaffolds with adequate physical properties for tissue engineering applications.

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: Current additive manufacturing (AM) processes are mainly focused on powder bed technologies, such as electron beam melting (EBM) and selective laser melting (SLM). However, the main disadvantages of such techniques are related to the high cost of metal powder, the degree of energy consumption, and the sizes of the components, that are limited by the size of the printing cell. The aim of the present study was to evaluate the environmental behavior of low carbon steel (ER70S-6) produced by a relatively inexpensive AM process using wire feed arc welding. The mechanical properties were examined by tension testing and hardness measurements, while microstructure was assessed by scanning electron microscopy and X-ray diffraction analysis. General corrosion performance was evaluated by salt spray testing, immersion testing, potentiodynamic polarization analysis, and electrochemical impedance spectroscopy. Stress corrosion performance was characterized in terms of slow strain rate testing (SSRT). All corrosion tests were carried out in 3.5% NaCl solution at room temperature. The results indicated that the general corrosion resistance of wire arc additive manufacturing (WAAM) samples were quite similar to those of the counterpart ST-37 steel and the stress corrosion resistance of both alloys was adequate. Altogether, it was clearly evident that the WAAM process did not encounter any deterioration in corrosion performance compared to its conventional wrought alloy counterpart.

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This study aims at evaluating the effect of microstructure imperfections on the corrosion fatigue performance of an ER70S-6 alloy produced by wire arc additive manufacturing (WAAM) process, in a 3.5% NaCl solution. For reference, a regular ST-37 alloy with relatively similar chemical composition was considered as a counterpart alloy. This was justified by the fact that the ER70S-6 alloy is usually used for conventional welding of ST-37 steel. The results obtained indicated that while the ST-37 alloy exhibited fatigue strength of 240 MPa in the corrosive solution, the additively manufactured ER70S-6 alloy showed fatigue strength of only 140 MPa. These differences were related to microstructural imperfections that are inherently produced during the WAAM process.

Increasing interest in biodegradable metals (Mg, Fe, and Zn) as structural materials for orthopedic and cardiovascular applications mainly relates to their promising biocompatibility, mechanical properties and ability to self-remove. However, Mg alloys suffer from excessive corrosion rates associated with premature loss of mechanical integrity and gas embolism risks. Fe based alloys produce voluminous corrosion products that have a detrimental effect on neighboring cells and extracellular matrix. In contrast, Zn does not appear to exhibit a harmful mode of corrosion. Unfortunately, pure zinc possesses insufficient mechanical strength for biomedical structural applications. The present study aimed at examining the potential of two new zinc based alloys, Zn-1%Mg and Zn-1%Mg-0.5%Ca to serve as structural materials for biodegradable implants. This examination was carried out under in vitro conditions, including immersion testing, potentiodynamic polarization analysis, electrochemical impedance spectroscopy (EIS), and stress corrosion cracking (SCC) assessments in terms of slow strain rate testing (SSRT). In order to assess the cytotoxicity of the tested alloys, cell viability was evaluated indirectly using Saos-2 cells. The results demonstrate that both zinc alloys can be considered as potential candidates for biodegradable implants, with a relative advantage to the Zn-1%Mg alloy in terms of its corrosion resistance and SCC performance.