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In this study, corrosion resistance of TiZrN-coated additively manufactured (3D-printed) 8620 steel has been separately studied in a 60–40 wt% NaNO3 + KNO3 molten salt and in an aqueous nitrate salt environment. Microstructural characterization of the as-built bare 3D-printed 8620 sample revealed martensitic microstructures. High-temperature corrosion analysis in molten nitrate salt revealed improved film stability and corrosion resistance of the coating. The coated 3D-printed sample showed no scale of corrosion products, whereas the bare 3D-printed sample exhibited a layer of corrosion products of 2.62 ± 0.24 µm thickness. Potentiodynamic polarization and electrochemical impedance spectroscopy tests in aqueous nitrate salts at room temperature exhibited an ~8-fold decrease in corrosion current density and a ~7-fold increase in charge transfer resistance, indicating enhanced corrosion resistance of the coated 8620. The coated wrought 8620 showed comparable corrosion resistance to that of the coated 3D-printed sample. However, in aqueous solution, the bare 3D-printed sample exhibited localized corrosion, whereas the bare wrought revealed uniform corrosion on the surface. [ABSTRACT FROM AUTHOR]

Materials with a disordered atomic structure, often termed glassy materials, are the focus of extensive research due to the possibility of achieving remarkable mechanical, electrochemical, and magnetic properties compared to crystalline materials. The glassy materials are observed to have an improved elastic modulus combined with a higher strength and hardness. Moreover, better corrosion resistance in different mediums is also observed for glassy solids, which is difficult to attain using conventional crystalline materials. As a result, the potential applications of metallic-glass systems are continually increasing. Amorphous materials are usually divided into two categories based upon their size. Materials with a thickness and diameter larger than the millimeter (mm) scale are termed as bulk metallic glass (BMG). However, the brittle nature of the bulk-sized samples restricts the size of metallic-glass systems to the micron (µm) or nanometer (nm) range. Metallic glasses with a specimen size in the scale of either µm or nm are defined as thin-film metallic glass (TFMG). In this review, BMGs and TFMGs are termed as metallic glass or MG. A large number of multi-component MGs and their compositional libraries reported by different research groups are summarized in this review. The formation of a multicomponent metallic glass depends on the constituent elements and the fabrication methods. To date, different unique fabrication routes have been adopted to fabricate BMG and TFMGs systems. An overview of the formation principles and fabrication methods as well as advantages and limitations of conventional MG fabrication techniques is also presented. Furthermore, an in-depth analysis of MG inherent properties, such as glass forming ability, and structural, mechanical, thermal, magnetic, and electrochemical properties, and a survey of their potential applications are also described. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) of metallic alloys offers a new avenue to print objects having complex geometries. This exclusive benefit of AM has made it an alternative route to conventional manufacturing. Importantly, additively manufactured (AMed) alloys often exhibit improved microstructures, which may provide better properties. The microstructure of an alloy can be tuned by controlling the processing parameters. This study includes an overview of the processing parameters that can influence the microstructural, mechanical, and corrosion properties of AMed alloys. Moreover, the effects of heat treatment on AMed alloys are also discussed. Among various processing parameters, it is observed that the laser power significantly influences the microstructure. The microstructures produced with high laser power are similar to heat-treated samples for 316L stainless steel (SS) and Ti6Al4V. Similarly, variation in scanning speed results in distinct morphology of grains in Ti6Al4V. Moreover, different AM processes, such as SLM and EBM, produce coarse and fine β grains, respectively, in Ti6Al4V. The fabrication of AlSi10Mg yields various sizes of melt pool due to different scanning strategies. Furthermore, mechanical properties such as microhardness is higher and the yield strength is lower for Ti6Al4V fabricated at lower laser power. The corrosion behavior of SLMed Ti6Al4V is different on the perpendicular and parallel planes to the build direction. Due to the increase in grain size after heat treatment, the corrosion resistance of AMed Ti6Al4V and AlSi10Mg is reduced. In contrast, heat treatment applied on 316L, Ti6Al4V, AlSi10Mg, and Inconel 718 is beneficial for mechanical properties. After the development of materials with optimized processing parameters, the research should be conducted on replacement of the wrought alloys with the AMed alloys. It is expected that new applications such as fuel cells and biomedical devices will utilize the AM technology to build parts in the recent future. [ABSTRACT FROM AUTHOR]

In the realm of biomaterials, metallic materials are widely used for load bearing joints due to their superior mechanical properties. Despite the necessity for long term metallic implants, there are limitations to their prolonged use. Naturally, oxides of titanium have low solubilities and form passive oxide film spontaneously. However, some inclusion and discontinuity spots in oxide film make implant to adopt the decisive nature. These defects heighten the dissolution of metal ions from the implant surface, which results in diminishing bio-integration of titanium implant. To increase the long-term metallic implant stability, surface modifications of titanium alloys are being carried out. In the present study, biomimetic coatings of plasma sprayed hydroxyapatite and titanium were applied to the surface of commercially pure titanium and Ti6Al4V. Surface morphology and surface chemistry were studied using scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. Cyclic potentiodynamic polarization and electrochemical impedance spectroscopy were carried out in order to study their electrochemical behavior. Moreover, cytotoxicity analysis was conducted for osteoblast cells by performing MTS assay. It is concluded that both hydroxyapatite and titanium coatings enhance corrosion resistance and improve cytocompatibility. [ABSTRACT FROM AUTHOR]

Fe-and Al-based thin-film metallic glass coatings (Fe 44 Al 34 Ti 7 N 15 and Al 61 Ti 11 N 28) were fabricated using magnetron co-sputtering technique, and their corrosion performances compared against wrought 316L stainless steel. The results of GI-XRD and XPS analyses demonstrated amorphous structure and oxide layer formation on the surface of the fabricated thin films, respectively. The potentiodynamic (PD) polarization test in chloride-thiosulfate (NH 4 Cl ​+ ​Na 2 S 2 O 3) solution revealed lower corrosion current (I corr) (0.42 ​± ​0.02 ​μA/cm2 and 0.086 ​± ​0.001 ​μA/cm2 Vs. 0.76 ​± ​0.05 ​μA/cm2), lower passivation current (I pass) (1.45 ​± ​0.03 ​μA/cm2 and 1.83 ​± ​0.07 ​μA/cm2 Vs. 1.98 ​± ​0.04 ​μA/cm2), and approximately six-fold higher breakdown potential (E bd) for Fe- and Al-based coatings than those of wrought 316L stainless steel. Electrochemical Impedance Spectroscopy (EIS) of both films showed 4- and 2-fold higher charge transfer resistance (R ct), 7- and 2.5-times higher film resistance (R f), lower film capacitance values (Q f) (10 ​± ​2.4 ​μS-sacm-2, and 5.41 ​± ​0.8 ​μS-sacm-2 Vs. 18 ​± ​2.21 ​μS-sacm-2), and lower double-layer capacitance values (Q dl) (31.33 ​± ​4.74 ​μS-sacm-2, and 15.3 ​± ​0.48 ​μS-sacm-2 Vs. 43 ​± ​4.23 ​μS-sacm-2), indicating higher corrosion resistance of the thin films. Cyclic Voltammetry (CV) scan exhibited that the passive films formed on the Fe- and Al-based coatings were more stable and less prone to pitting corrosion than the wrought 316L stainless steel. The surface morphology of both films via SEM endorsed the CV scan results, showing better resistance to pitting corrosion. Furthermore, the thermal analysis via TGA and DSC revealed the excellent thermal stability of the thin films over a wide temperature range typically observed in oil-gas industries. [Display omitted] • Al 61 Ti 11 N 28 and Fe 44 Al 34 Ti 7 N 15 thin-film metallic glass fabrication via sputtering. • Six-fold higher breakdown potential of TFMGs compared to wrought 316L SS. • Both the thin films showed 2 to 4 times higher charge transfer resistance. • Higher resistance against pitting corrosion of TFMGs compared to wrought 316L SS. • TFMGs showed excellent thermal stability up to 1000 ​°C. [ABSTRACT FROM AUTHOR]

Magnesium alloys have raised an immense amount of interest to many researchers because of their evolution as a new kind of third generation materials. Due to their biocompatibility, density, and mechanical properties, magnesium alloys are frequently reported as prospective biodegradable implant materials. Moreover, magnesium alloys experience a natural phenomenon to biodegrade in aqueous solutions due to its corrosion activity, which is excellent for orthopedic and cardiovascular applications. However, a major concern with such alloys is fast and non-uniform corrosion degradation. Controlling the degradation rate in the physiological environment determines the success of biodegradable implants. In this investigation, three different grades of magnesium alloys: AZ31B, AZ91E and ZK60A were studied for their corrosion resistance and biocompatibility. Scanning electron microscopy, energy dispersive spectroscopy, atomic force microscopy and contact angle meter are used to study surface morphology, chemistry, roughness and wettability, respectively. Additionally, the cytotoxicity of the leached metal ions was evaluated by using a tetrazolium based bio-assay, MTS. [ABSTRACT FROM AUTHOR]

• Ti 51 Si 24 Ni 14 Nb 11 and Fe 40 Ti 30 Al 18 Si 12 TFMGs are developed via magnetron sputtering. • TFMGs exhibit superior corrosion resistance compared to cp-Ti and 316L SS. • TFMGs show 7–10 times smaller i corr , 4-6 times higher R ct , & 200-800 mV higher E bd. • Better combination of hardness and modulus of TFMGS for bioimplant applications. • Amorphous structure and stable passive film contribute to superior performance. This work investigates electrochemical response and mechanical properties of quaternary Ti 51 Si 24 Ni 14 Nb 11 and Fe 40 Ti 30 Al 18 Si 12 (at.%) thin film metallic glasses (TFMGs) developed using magnetron co-sputtering. Both TFMGs demonstrate superior corrosion resistance registering ∼7 to 10 times smaller corrosion current density, ∼200 to 800 mV higher break-down potential, and ∼4 to 6 times higher charge transfer resistance in phosphate buffer saline (PBS) and 0.9% sodium chloride (NaCl) compared to conventional Ti- and Fe-based biomaterials, e.g., commercially pure Ti (cp-Ti) and 316L stainless steel (SS). The enhanced anti-corrosive behavior of the quaternary films is attributed to their amorphous structures and relatively more protective passive oxide films. In addition, nano-indentation experiment reveals more than 2 times higher hardness and ∼10 to 40 GPa lower elastic modulus of the TFMGs compared to conventional biomaterials. The combination of obtained anti-corrosive behavior and mechanical properties promotes the fabricated films as potential candidates for future bio-implant applications. [ABSTRACT FROM AUTHOR]