The structural integrity of SA 516 Grade 70 steel pressure vessels critically depends on welding procedures and resultant microstructures. Finite element analysis (FEA) modeled the thermal profile of welded joints and was validated by the observed microstructural transformations. High-temperature excursion in the heat-affected zone (HAZ) transformed polygonal ferrite into Widmanstätten ferrite (αw), while acicular ferrite (αac) and allotriomorphic ferrite (αal) phases formed in the weld zone (WZ). Corrosion testing revealed preferential dissolution of the WZ due to a higher galvanic current (135.4 µA/cm²) compared to the base metal-HAZ interface (104.6 µA/cm²). This galvanic interaction could be detrimental due to a low exposed area ratio between the WZ and base metal. Impact toughness dropped significantly from 140 J at 20 °C to 13 J at −40 °C, transitioning the fracture mode from ductile to brittle, as confirmed by fractographic analysis.

Owing to the low cost, ease of fabricability, good mechanical properties, corrosion resistance and biocompatibility of the 316L stainless steel (SS), this material is considered a suitable choice for orthopedic applications. Based on its properties and large utilization in orthopedics, this review focuses on the importance of additively manufactured (AM) 316L stainless steel. Owing to the large flexibility of the additive manufacturing process, the microstructure of the 316L SS can be easily tuned to modify the mechanical, corrosion and biological properties. To elucidate the benefits of additively manufactured 316L stainless steel, the properties of the selective laser melted (SLM) 316L stainless steel and wrought 316L stainless steel are compared. Particularly, the unique features of the SLM 316L stainless steel have been discussed in detail. The existing challenges associated with the additive manufacturing processes and implications of their widespread application are also highlighted. A brief overview of the biological properties and reactions sequence of the host immune system, i.e. tissue response, the activation of acute and chronic inflammatory processes and immunological reactions, is also provided to understand the reasons for implant failure or rejection by the body.

This study examines repeated failures in a 33-year-old waste heat recovery boiler made of ASTM A204-Grade A steel. Cracks and NOx leakage reoccurred 3.2 years after repairs, with inspections revealing branched intergranular cracks near weld seams due to prolonged high-temperature exposure. Microstructural analysis identified spheroidized carbides, pearlite disintegration, and creep cavity formation, weakening the material. Elevated internal surface temperatures calculated using the Larson–Miller parameter (PLM) and heat retention from oxide scale buildup accelerated degradation. The findings underscore the need for strict design adherence, effective thermal management, and regular inspections to maintain WHRB integrity and prevent future failures.

The Al-Zn sacrificial anodes are widely used for cathodic protection in marine steel structures. This study evaluates the impact of bismuth addition on the electrochemical properties of the Al-Zn sacrificial anode in artificial seawater. The microstructure analysis confirms the presence of uniformly distributed intermetallic β-AlFeSi and spherical Bi particles within the α-Al matrix. The open circuit potential (OCP) comparison between Al-Zn-Bi and carbon steel reveals a potential difference of approximately 400 mV, indicating sufficient cathodic protection for the steel. Electrochemical impedance measurements indicate the initial hindered dissolution of the anode due to surface film formation, which later dissociates due to the aggressive attack of Cl– species in the electrolyte. The sufficiently negative surface potential (-0.875 V vs. Ag/AgCl) observed at 10 mA/cm² demonstrates the suitability of anode for fulfilling the cathodic protection criteria of steel structures.

Thermo-kinetic (TK) diagrams are developed for an additively manufactured (AM) CoCr alloy in 0.1 M Na2SO4 in the pH range of 4 to 9 at a constant temperature of 37 degrees C. The effect of 100 ppm chloride in these solutions was also investigated. TK diagrams can be used to estimate the corrosion rate of the AM CoCr alloy as a func-tion of solution potential and pH. For instance, based on the potentiodynamic polarization results obtained at an optimized potential sweep rate (1.0 mV/s), the passive film had reduced stability at potential > 0.2 VSHE, within 5 < pH < 7, and in the presence of 100 ppm Cl-. Similarly, the CoCr alloy has poor corrosion resis-tance at potentials lower than 0.8 V vs SHE within 5 < pH < 7, which may be due to the conversion of Cr (OH)3 into soluble CrOH2+ species. The TK diagrams can be used to predict the corrosion rate of CoCr alloys during changes in pH, which may be important during wound healing for implants.

The rubber bands used in the track chains of excavators, known as track pin rubber bands, frequently experience failures due to factors such as their heavyweight, fast speed, sharp objects on off-road paths, shocks, vibrations, accumulated heat (generated during operation), and track tension. To identify the main cause of these failures, we conducted a failure analysis by evaluating their chemical compositions, morphological, mechanical, and thermal properties. For this study, four different types of failed rubber bands, designated as RB1, RB2, RB3, and RB4, were collected from the track pins of four distinct excavator track chains. None of the selected rubber bands passed the 1000 km running trial. RB1 failed after covering 650 km, RB2 failed after 250 km, RB3 after 400 km, and RB4 after 800 km. Both mechanical and thermal properties are dependent on the chemical formulations of the rubber bands, and all the failed rubber bands exhibited poor chemical formulations. RB1 showed a Schallamach wave on the outer used surface, indicating significant plastic deformation before fracture. In contrast, the other failed rubber bands (RB2, RB3, and RB4) displayed severe mechanical degradation with surface defects such as deep grooves, catering or pitting, micro-cracks, and scars. Thermogravimetric analysis further supported the cause of failure, revealing higher total mass loss and lower residue mass percentages.

For the hydrogen economy to be viable, new, and efficient production techniques are of prime importance. Water electrolysis offers high production of hydrogen but due to slow reaction rates on many electrode surfaces, electrocatalysts are needed. However effective electrocatalysts, such as platinum and rhenium, may be impractical for economic operation. Therefore, research in this area has been focused on finding materials that can replace these expensive electrocatalysts. The electrocatalytic behaviour of stainless steel towards water dissociation is presented. The use of two widely available and comparatively inexpensive stainless steels i.e., 304 and 316L, in a variety of forms, i.e., mesh, solid electrode, and adsorbed nanoparticles is discussed. Results of microscopic characterization are compiled to illustrate how surface modification of these substrates affects their electrocatalytic ability. The crystallographic orientations i.e. (111) and (220) in the microstructure of stainless steel are believed to be effective in catalytic dissociation of H2O. The catalytic activity and long-term stability measurements of stainless steels have yielded results similar to or sometimes better than-those of the noble electrocatalysts. The review briefly captures the current progress in HER and OER electrocatalysis on stainless steels and highlights the possible research solutions to overcome existing challenges i.e., lack of active centers, the surface modification needed, poisoning of active species and an overall low stability, the solution to which could make stainless steel a viable replacement for the precious metals electrocatalysts.

The effect of cold rolling and post-rolling heat treatment on the microstructural and electrochemical properties of the 316L stainless steel was investigated. Two-pass and four-pass cold-rolled stainless steel specimens were heat-treated by annealing at 900°C followed by quenching in water. During the cold rolling, the microstructure of the as-received specimen transformed from austenite to strain-induced α’-martensite due to significant plastic deformation that also resulted in significant grain elongation (i.e., ∼33% and 223% increases in the grain elongation after two and four rolling passes, respectively). The hardness of the heat-treated as-received specimen decreased from HV 190 to 146 due to the recovery and recrystallization of the austenite grain structure. The cyclic polarization scans of the as-rolled and heat-treated specimens were obtained in 0.9wt% NaCl solution. The pitting potential of the four-pass rolled specimen was significantly increased from 322.3 to 930.5 mV after post-rolling heat treatment. The beneficial effect of the heat treatment process was evident from ∼10-times-lower corrosion current density and two-orders-of-magnitude-lower passive current density of the heat-treated specimens compared with those of the as-rolled specimens. Similarly, appreciably lower corrosion rate (3.302 × 10−4 mm/a) and higher pitting resistance (1115.5 mV) were exhibited by the post-rolled heat-treated specimens compared with the as-rolled 316L stainless steel specimens.

This research work aims to investigate the effect of the aerobic bacterium, Pseudomonas aeruginosa on the mechanical and electrochemical properties of the 316L stainless steel and α-brass. These properties of both the alloys were determined after 7 days of exposure to the controlled and inoculated media at 37°C. The microstructural and electrochemical test results revealed the deleterious effects of Pseudomonas aeruginosa. After exposure to the inoculated medium, the scanning electron microscopy (SEM) results showed the larger pitting and formation of relatively dense biofilm on α-brass compared to 316L stainless steel. The tensile strength and hardness of 316L stainless steel were slightly affected after exposure to the controlled and inoculated media. After exposure to the controlled medium and inoculated media, the tensile strength of the α-brass was least affected but a significant decrease in the hardness (from 165 HV to 124 HV) was observed due to the severe attack induced by the Pseudomonas aeruginosa. Similarly, the open-circuit potential of the 316L stainless steel in the inoculated medium was measured to be less active (−410 mV vs Ag/AgCl) than α-brass (−550 mV vs Ag/AgCl). In the inoculated medium, potentiodynamic polarization curves confirmed the severe attack of Pseudomonas aeruginosa on α-brass (7.15 × 10−2 mm/year) compared to 316L stainless steel which registered a corrosion rate of 5.14 × 10−4 mm/year.

This research aims to investigate the effect of chemical treatment on the integrity of the epoxy coating applied on mild steel substrates. Grit blasted steel samples were chemically treated in 10 vol.% NaOCl solution, 10 vol.% CrCl3 and 30 vol.% H3PO4–5 vol.% HNO3 solutions prior to coating application. Post-cleaning surface morphology and chemical composition revealed the formation of oxidation products on steel surface. Under optimized conditions, a dry film thickness of 135 ± 3 μm of epoxy coating was achieved. The CT2 sample (pre-treated with CrCl3) presented higher coating adhesion strength (∼4.12 MPa) and the lowest rust area of ∼0.03% compared to other chemically treated samples during 720 h of immersion in 5 wt.% NaCl solution. The coating degradation mechanism was evaluated by electrochemical impedance spectroscopy (EIS) after 24, 48, 72 and 120 h of immersion in 3.5 wt. % NaCl solution. EIS analysis of the coated samples pretreated with NaOCl and CrCl3 solutions exhibited low water uptake and limited corrosion due to hindrance in the diffusion of ionic species through the coating. However, coated steel samples pretreated in acidic solutions displayed appreciable corrosion damage as confirmed from salt spray and immersion tests. For instance, the delamination of the CT3 and CT4 (acid pre-treated) coatings was confirmed from the EIS analysis., which represented the formation of a double layer and occurrence of faradaic (corrosion) reactions as the coating-substrate interface, resulting in ∼15%–30% delamination in 120 h of exposure.

The main objective of this study is to integrate two energy-intensive metallurgical processes, Cu extraction from CuFeS2 and Zn electrowinning, into a battery-like device that could incentivize renewable energy use at remote mining locations. In this device, Cu extraction and Zn electrowinning occur simultaneously during the charge cycle. During discharge, the device, referred to as a trifunctional battery (TFB), can supply back to an electrical circuit a portion of the stored energy. The re-dissolution of Zn during discharge and reversible reactions at a chalcopyrite slurry electrode are responsible for this energy release. The high initial specific energy (388 Wh-g(-1) at 0.5 C discharge rate) registered by this setup decreased to 50 Wh-g(-1) during the initial 15 galvanostatic charge discharge cycles and remained almost constant in the subsequent 85 cycles. The low coulombic (approximate to 50%) and energy efficiencies (approximate to 40%) demonstrated by the TFB occurred at maximum (23%) Cu extraction from CuFeS2. A feature of the TFB is that the normally unwanted irreversible reactions that occur in traditional batteries are in fact desirable in the TFB, i.e., they lead to valuable Cu extraction in addition to energy storage. (C) 2019 Elsevier Ltd. All rights reserved.

PurposeThis study/paper aims to the authors applied low “Si” ions dose over cp-Ti-2, and the potent dose level was optimized for adequate corrosion resistance and effective proliferation of stem cells.Design/methodology/approachThe cp-Ti surface was modified by silicon (Si) ions beam at 0.5 MeV in a Pelletron accelerator. Three different ion doses were applied to the polished samples, and the surface was characterized by XRD and AFM analysis.FindingsAt moderate “Si” ion dose (6.54 × 1012ions-cm−2), the potential shifted to a noble value. The small “icorr” (1.22 µA.cm−2) and relatively large charge transfer resistance (43.548 kΩ-cm2) in the ringer‘s lactate solution was confirmed through Potentiodynamic polarization and impedance spectroscopy analysis. Compared to cp-Ti and other doses, this dose level also provided the effective proliferation of mesenchymal stem cells.Originality/valueThe dosage levels used were different to previous work and provided the effective proliferation of mesenchymal stem cells.

Foundry Refractory Coatings are used to improve surface finish of grey iron castings and reduces the re-work cost that covers the surface defects. Present research was concentrated on qualitative and quantitative analysis of commercial coatings through X-ray Diffraction and Energy Dispersive Spectroscopy respectively. A number of coating compositions were prepared by means of refractory fillers, binders and particle size as most concern parameter and validated through Design of Experiment. Ultimately, three types of coating formulation were developed by coating constituents and characterized using X-ray Diffraction. Fe2O3 and SiO2 were determined as major phases in all coating samples. Particle size of 75 microns was used for smooth surface finish. Gray iron casting had been produced without disturbing the mechanical properties and graphite distribution. Surface defects were covered by one of the best refractory coating recipe.

Phosphate chemical conversion (PCC) coatings have been investigated for improving surface protection of magnesium alloys in aerospace, automobile, electronics, sports goods, and biomedical applications. Zinc, calcium, zinc–calcium, manganese, magnesium, molybdate, and dihydrogen manganese polyphosphate conversion coatings are widely used for improving appearance, bonding strength, corrosion resistance, wear resistance, biocompatibility, and biodegradability of Mg and its alloys. As an overview, several main types of PCC coatings for Mg alloys, their properties, and behavior in different environments particularly for biomedical applications have been discussed. The pre-surface treatments, deposition mechanism, as well as process parameters, i.e., bath compositions, temperature, time, and pH, are also elaborated in a separate section. Additionally, the main types of PCC coatings applied on Mg and its alloys, their microstructural features, and their biological performance are briefly described. Finally, applicable characterization techniques to evaluate the properties of PCC-coated Mg alloys were also discussed.

Protective organic coatings are being widely used to protectsteel structures and equipment form corrosion damages. Corrosionthreat to commercial infrastructure is a monetary and engineeringproblem, while the expense of the coatings is a little part of thewhole cost of the undertaking...

The commercially pure titanium (cpTi–2) was anodized at high potentials (≥10 V) in an organic solution containing fluoride ions. The morphology of the nanotubular structure (NTs) depends on the applied electric field as evaluated from the scanning electron microscope images. The internal diameter of the NTs increased from ∼26 to ∼150 nm with the increase in potential from 10 to 60 V. The growth of Ti6O NTs along the (110) and (112) crystallographic planes and increase in crystallite size as determined from x-ray diffraction patterns is found to be a function of applied potential during the anodizing process. The electrochemical behavior of these anodized samples was evaluated in 1 wt% NaCl solution through potentiodynamic polarization and electrochemical impedance spectroscopy test methods. The NTs formed at high potentials (50 and 60 V) represented relatively smaller Tafel slopes (ba and bc) and larger corrosion (icorr) and passive (ip) current compared to NTs developed at low potentials. These results were in support with the improved kinetic response of the Ti6O film, predicted from the simulation of impedance spectra. The p-type semiconductive behavior and an order of magnitude higher charge carrier concentration were also exhibited by NTs formed at potential >40 V as confirmed from Mott Schottky analyses.

The rapid corrosion of magnesium alloys in physiological environment constraints its applications to employ it as a biodegradable implant material. AZ31 and ZK60 alloys were executed to anodization in alkaline solution as a function of time and investigated their electrochemical and mechanical properties. The scanning electron microscopy reveals the compact passive film formation subsequently to anodization. The high-resolution spectra of x-ray photoelectron spectroscopy confirmed the existence of MgO, Mg(OH)(2) and traces of CO3-2 within the anodized layer. The quasi-static with displacement-controlled mode of indentation was performed to investigate the mechanical properties of the anodized films. Anodized ZK60 has an average hardness of similar to 0.49 GPa, greater than the hardness of anodized AZ31-Ano (0.35 GPa). Similarly, the stiffness and film elastic modulus for anodized ZK60 were higher when compared with anodized AZ31. The surface roughness of anodized ZK60 (473.54 +/- 51.61 nm) was higher than that of anodized AZ31 (112.11 +/- 11.31 nm). The potentiodynamic polarization scans for AZ31 showed corrosion current density of 4.46 mu A/cm(2) (untreated) and 394.8 e(-3) mu A/cm(2) (anodized), while in ZK60 corrosion current densities values shifted from 12.05 mu A/cm(2) (un-treated) to 714.8 e(-3) mu A/cm(2) (anodized). Similarly, electrochemical impedance spectroscopy indicated enhanced charge transfer resistance for anodized AZ31 (1.164 K Omega-cm(2)) and ZK60 (1.911 K Omega-cm(2)) when compared with untreated AZ31 (28.3 K Omega-cm(2)) and ZK60 (0.481 K Omega-cm(2)). Furthermore, MC3T3 preosteoblast cells on the anodized surfaces caused no adverse effects in regards to biocompatibility.

We report the first use of a CuFeS2 froth flotation mineral concentrate (MC) as an energy storage material in a fixed bed flow cell (FBFC). The performance of a graphite felt (GF) MC negative electrode (GF-MC) was also compared to a synthetic CuFeS2 electrode in the same FBFC. The Fe(II)/Fe(III) redox reaction (in the presence of Cu(II)) on the GF positive electrode (GF-Fe/Cu) supported the charge/discharge process. The kinetic parameters calculated from individual cyclic voltammetry scans of negative and positive electrodes revealed that the electrochemical processes in the FBFC were quasi-reversible. In cell C-1 (GF-CuFeS2/GF-Fe/Cu), a continuous increase in specific capacity (similar to 9-48 mAh g(-1)) and energy (2-6.3 Wh kg(-1)) in 500 charge/discharge cycles was attributed to the capacitive behavior of the S-2(2-)/S2- species present on the CuFeS2. However, during 400 GCD cycles of C-2 (GF-MC/GF-Fe/Cu), a monotonic increase in the specific capacity (20-49 mAh g(-1)) and energy (3.5-8.5 Wh kg(-1)) was associated with an additional capacitive response from FeS2 in the MC. Advantageously, 10.3 and 12.7% Cu was also extracted from the C-1 and C-2 cells, respectively, which is unique to this system and provides a positive offset for the relatively low energy storage compared to existing battery systems. An observed improvement in the specific capacity during repetitive cycling was related to the presence of Cu and sulfide sulfur species on the CuFeS2 particles as revealed from the characterization of retrieved CuFeS2. (C) 2018 Elsevier Ltd. All rights reserved.

In the quest of finding an economical, yet efficient material, the idea of fabricating 316L stainless steel using additive manufacturing technology was explored to produce material with refined sub-granular structure. The surface of the stainless steel was further chemically treated with an etching solution to expose the grain boundaries. The grain boundary enriched surface resulted in more active sites for the oxygen evolution reaction (OER) in additively manufactured treated (AM-T) 316L stainless steel. AM-T sample manifests enhanced catalytic activity for OER with an overpotential of 310 mV to draw a 10 mA/cm(2) current density, along with a lower Tafel slope of 42 mV/dec compared to AM and wrought samples. These features were validated from the increased double-layer capacitance of AM-T and approximately 1.5 times larger electrochemically effective surface area of AM-T due to etching treatment compared to the wrought sample. Furthermore, AM-T also possesses stable activity retention for 100 h at a current density of 10 mA/cm(2). (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.