Evaluation of corrosion behavior in artificial saliva of 2507 and 2205 duplex stainless steel for orthodontic wires before and after heat treatment

Fabrication of Mechanically Alloyed Super Duplex Stainless Steel Powder-Modified Carbon Paste Electrode for the Determination of Methylene Blue by the Cyclic Voltammetry Technique

Alloys with an equal balance of ferrite and austenite provide super duplex stainless steel (DSS) with enhanced strength and corrosion resistance. This study utilized mechanical alloying to produce nanostructured super duplex stainless steel powders for the identification of methylene blue dye in wastewater. High-energy particle grinding was employed to create the SAF-2507 DSS powders. To electrochemically oxidize methylene blue dye in wastewater, a modified carbon paste electrode (DSS-MCPE) was developed. Methylene blue, a water-soluble cationic colorant extensively used in the paper, pulp, and textile industries, poses a threat to human health and water supplies when improperly disposed of. DSS-MCPE demonstrated a significant current response, indicating its capability to detect methylene blue dye in a pH range of 6-8. The experiment revealed that 2 mg of DSS-MCPE produced a maximum current response of 72.22 μA, facilitating the effective electrooxidation of methylene blue dye in wastewater. Furthermore, the investigation demonstrated that the active surface area of the 2 mg of DSS-MCPE (0.478 cm2) was greater than that of the bare carbon paste electrode (BCPE) (0.054 cm2). The increased active surface area was correlated with an enhanced current response. The strong interaction between methylene blue molecules at the interface of the produced 2 mg of DSS-MCPE contributed to the observed increase in anodic current across methylene blue concentrations ranging from 0.1 to 0.6 mM.

On the Biomechanical Performances of Duplex Stainless Steel Graded Scaffolds Produced by Laser Powder Bed Fusion for Tissue Engineering Applications

This experimental study aims to extend the know-how on biomechanical performances of duplex stainless steel (DSS) for tissue engineering applications to a graded lattice geometry scaffold based on the F53 DSS (UNS S32750 according to ASTM A182) produced by laser powder bed fusion (LPBF). The same dense-out graded geometry based on rhombic dodecahedral elementary unit cells investigated in previous work on 316L stainless steel (SS) was adopted here for the manufacturing of the F53 DSS scaffold (SF53). Microstructural characterization and mechanical and biological tests were carried out on the SF53 scaffold, using the in vitro behavior of the 316L stainless steel scaffold (S316L) as a control. Results show that microstructure developed as a consequence of different volume energy density (VED) values is mainly responsible for the different mechanical behaviors of SF53 and S316L, both fabricated using the same LPBF manufacturing system. Specifically, the ultimate compressive strength (σUC) and elastic moduli (E) of SF53 are three times and seven times higher than S316L, respectively. Moreover, preliminary biological tests evidenced better cell viability in SF53 than in S316L already after seven days of culture, suggesting SF53 with dense-out graded geometry as a viable alternative to 316L SS for bone tissue engineering applications.

Biomineralization of 2304 duplex stainless steel with surface modification by electrophoretic deposition

A hydroxyapatite (HAp) coating on 2304 duplex stainless steel (DSS) through an electrophoretic deposition process has been investigated in this work. The deposition voltage was 30 V with a time of 2 min. Field emission scanning electron microscopy and energy dispersive X-ray spectroscopy analyses were used for the microstructural and chemical examination of coatings, respectively. The Ca to P ratio for the nano HAp coating on 2304 DSS has been determined as equal to 1.642. It was observed from X-ray diffraction patterns that HAp nanoparticles were successfully combined into the substrate. The corrosion behavior of all samples was tested in simulated body fluid using a potentiodynamic polarization study. A homogeneous structure with a thin crack-free layer was obtained. Moreover, the porosity of this coating was very low leading to a high corrosion resistance, thus promoting good biocompatibility.

Optimization of clinically applied orthodontic archwire electrothermal treatment conditions by heat tint and mechanical properties: An experimental study

OBJECTIVE

Electric resistance heat treatment procedures are performed by most orthodontists; however, the effects of electrothermal treatment on the mechanical properties, surface morphology, phase transition, colour and arch width of stainless steel archwires remain controversial and are worthy of investigation.

MATERIALS AND METHODS

Stainless steel archwires (0.017×0.025 and 0.019×0.025 inches) were heat-treated using a spot-welder machine at a power setting of 3 for 5, 10, 15 or 20s and were then cooled in air. After the heat treatment, we analysed the surface morphology of the samples by scanning electron microscopy (SEM) and the flexural modulus with a universal testing machine. The changes in phase and the austenite content after heat treatment were determined by X-ray diffraction (XRD). The changes in the colour of the sample were analysed by a digital single-lens reflex (DSLR) camera, and the arch width changes were measured with Vernier calippers.

RESULTS

The flexural modulus and austenite content of the orthodontic stainless steel archwires increased after heat treatment (P<0.05). The colour changed from silver to yellow-brown-blue. Heat treatment of the stainless steel wires increased the inter-canine and inter-molar widths only when the amount of heat received was low.

CONCLUSION

Heat treatment of stainless steel orthodontic archwires using an electric resistance device is an effective and convenient method to improve their flexural modulus. The colour of the wire surface after heat treatment can help determine the heating conditions, and the maximum flexural modulus of the stainless steel wires was obtained when the colour changed to brownish yellow.