•Bromelain, an environmental-friendly compound was evaluated as corrosion inhibitor.•The % η of bromelain reached 97.6% at 1000 ppm in 1 M HCl.•Bromelain behaved as mixed type of inhibitor.•The ...adsorption of bromelain on low carbon steel surface obeys Langmuir adsorption model.
The anticorrosion behavior of bromelain on low carbon steel (LCS) in 1 M HCl solution was studied employing weight loss, potentiodynamic polarization measurement (PDP), electrochemical impedance spectroscopy (EIS), UV–visible spectrophotometry, and surface assessment techniques like scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX) at 308–338 K. The obtained results suggest that bromelain is an excellent corrosion inhibitor and its inhibition efficiency (%η) is both concentration and temperature dependent. %η is observed to increase with an increase in bromelain concentration and an increase in electrolyte temperature. The maximum %η of 97.6% is observed at bromelain concentration of 1000 ppm at 338 K. The inhibitor adsorption on the LCS surface is in accordance with the Langmuir adsorption isotherm. As evidenced by PDP measurements, bromelain behaves as a mixed-type inhibitor and controls both anodic and cathodic processes. Adsorption free energy of the bromelain on LCS surface together with an increase in %η with the rise in temperature is suggestive of chemical adsorption. SEM micrographs show a smoother surface for inhibited LCS specimen. Analysis of variance statistically compare the difference existing between inhibition efficiencies from gravimetric, PDP and EIS technique and suggests that they are not significantly different.
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•Ti microalloying increased the nucleation sites for Cu-rich particles.•The addition of Ti impeded the enrichment of Cu in Cu-rich particles.•Ti microalloying made Cu-rich particles ...maintain semi-coherent 3R or 9R structure in tempering process.•By adding 0.05 wt% Ti, the precipitation strengthening of Cu-rich particles increased from 46 MPa to 248 MPa.
This present work aims to improve the precipitation strengthening of nanoscale Cu-rich particles in high-strength low carbon steel by Ti microalloying. Ti microalloying increased the density of small-angle boundaries and dislocations, which increased the nucleation sites and refined the dimension of Cu-rich particles. By adding 0.05 wt% Ti, the size of Cu-rich particles were refined from 22 nm to 7 nm. The structure of Cu-rich particles in Ti-free steel was incoherent FCC-Cu, whose mismatch degree with α-Fe matrix was 0.28. By adding 0.02 wt% and 0.05 wt% Ti, the structure of Cu-rich particles transformed into semi-coherent 3R-Cu and 9R-Cu, respectively. Meanwhile, the mismatch degrees between Cu-rich particle and α-Fe matrix decreased to 0.24 and 0.21, respectively. The refinement of Cu-rich particles increased the precipitation strengthening from 46 MPa to 248 MPa.
A lamella structured low-carbon steel plate with bimodal grain size distribution (LSBG steel) was produced by a two-step warm rolling and subsequently annealing, and its mechanical properties, ...strengthening and toughening mechanisms were studied. The heterogeneous lamellar structure is characterized with ultrafine-grained (UFG) lamellae (with average grain diameter about 1 μm) embedded in coarse-grained (CG) lamellae matrix. The LSBG steel shows an improved combination of strength and toughness when compared with corresponding CG specimens, and also evades strength-ductility trade-off compared with UFG ones. When comparing with initial CG steel, the yield strength and tensile strength are increased by 87.4% and 35% respectively, but the ductility is only with a small sacrifice, and the ductile-to-brittle transition temperature is significantly decreased from about −70 °C to −110 °C. The improved strength is mainly attributed to ultrafine grain strengthening, and the reasonable ductility can be attributed to both the bimodal grain size and the lamellar structure as they can increase the work hardening rate by the accumulation of geometrically necessary dislocations in their vicinity. And the improved toughness of the LSBG steel is thought to be mainly attributed to grain refinement and the lamellar structure.
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•Lamella structured steel with bimodal grain size distribution (LSBG) was produced.•The LSBG steel shows an improved combination of strength and toughness.•Both grain refinement and the lamellar structure contribute to strength improvement.•Bimodal grain size and the lamellar structure contribute to good ductility.•Toughness improvement of the LSBG steel is mainly attributed to grain refinement.
•Hydrogen damage of the boiler evaporator tube, made of carbon steel, was investigated.•The high temperature hydrogen attack is a primary cause of boiler tube fracture.•Postmortem analysis of the ...hydrogen embrittlement mechanisms was carried out.•Experiment is based on the correlation of mechanical properties to SEM fractography.•Simultaneous action of the hydrogen embrittlement mechanism, HELP+HEDE, were detected.
Many efforts have been made to understand the effects of hydrogen on steels, resulting in an abundance of theoretical models and papers. However, a fully developed and practically applicable predictive physical model still does not exist industrially for predicting and preventing hydrogen damage. In practice, it is observed that different types of damages to industrial boiler components have been associated with the presence and localization of hydrogen in metals. In this paper, a damaged boiler tube made of grade 20 – St.20 (or 20G, equivalent to AISI 1020) was investigated. The experimental research was conducted in two distinctive phases: failure analysis of the boiler evaporator tube sample and subsequent postmortem analysis of the viable hydrogen embrittlement mechanisms (HE) in St.20 steel. Numerous tested samples were cut out from the boiler tubes of fossil fuel power plant, damaged due to high temperature hydrogen attack (HTHA) during service, as a result of the development of hydrogen-induced corrosion process. Samples were prepared for the chemical composition analysis, tube wall thickness measurement, tensile testing, hardness measurement, impact strength testing (on instrumented Charpy machine), analysis of the chemical composition of corrosion products – deposit and the microstructural characterization by optical and scanning electron microscopy – SEM/EDX. The HTHA damage mechanism is a primary cause of boiler tube fracture. Based on the multi-scale special model, applied in subsequent postmortem investigations, the results indicate a simultaneous action of the hydrogen-enhanced decohesion (HEDE) and hydrogen-enhanced localized plasticity (HELP) mechanisms of HE, depending on the local concentration of hydrogen in investigated steel. The model is based on the correlation of mechanical properties to the SEM fractography analysis of fracture surfaces.
•The effect of electro discharge machining (EDM) parameters on the magnetic properties of extra-low-carbon steel has been experimentally extracted, and the optimum levels of the parameters have been ...determined for optimum magnetic properties.•The results show that the optimum parameter levels for the lowest magnetic coercive force include the pulse-on time of 160 microseconds, pulse-off time of 60 microseconds, 16 Amps current, and 70 Volts gap voltage. Also, for the lowest remanence magnetization, the pulse-on time, pulse-off time, the current, and gap voltage are 50 microseconds, 60 microseconds, 16 Amps, and 90 Volts, respectively.•The optimum parameters for maximum saturation magnetization are 50 microseconds, 90 microsecond, 12 Amps and 80 Volts for the pulse-on time, pulse-off time, the current, and gap voltage respectively.
Extra-low-carbon steels are becoming increasingly important for their high magnetic permeability, and reasonable price in industrial applications such as magnetic suspension systems, actuators, and sensors. The application of these steels to the aforementioned parts and industries depends on their magnetic properties. The various manufacturing processes used to make equipment and tools based on this kind of steels affect their magnetic properties. In this study, the effect of electro discharge machining (EDM) parameters on the magnetic properties of extra-low-carbon steel has been experimentally extracted, and the optimum levels of the parameters have been determined for optimum magnetic properties. The selected parameters include pulse-on time, pulse-off time, current, and gap voltage, and the design of experiments was done by the Taguchi method. After machining and preparing the specimens, their hysteresis curves were measured using vibrating-sample magnetometer (VSM), and the magnetic properties of the machined extra-low-carbon steels were calculated. The results show that the optimum parameter levels for the lowest magnetic coercive force include the pulse-on time of 160 microseconds, pulse-off time of 60 microseconds, 16 Amps current, and 70 Volts gap voltage. Also, for the lowest remanence magnetization, the pulse-on time, pulse-off time, the current, and gap voltage are 50 microseconds, 60 microseconds, 16 Amps, and 90 Volts, respectively. The optimum parameters for maximum saturation magnetization are 50 microseconds, 90 microsecond, 12 Amps and 80 Volts for the pulse-on time, pulse-off time, the current, and gap voltage respectively.
Ternary surface hardening layers were prepared on the Q235 low-carbon steel by plasma electrolytic borocarbonitriding(PEB/C/N) under constant voltage of 260–300 V for 30 min. The microstructure, ...phase components and hardness depth profiles of the B + C + N ternary hardening layers were examined. The ternary hardening layers were composed of a boride layer with single Fe2B phase and a transition layer. The thickness of modified boride layers on the PEB/C/N samples was about 10 μm, 15 μm and 22 μm at 260 V, 280 V and 300 V, respectively. The maximum hardness of boride layer was 2400 HV for the 300 V PEB/C/N sample. The surface free energy of bare Q235 steel and PEB/C/N samples at 260, 280 and 300 V were 41.084, 32.039, 26.906 and 25.726 mJ/m2, which were calculated on the basis of their contact angles for water and n-hexadecane. Furthermore, the hardening layers exhibited excellent corrosion behavior due to the improved hydrophobicity for the dense boride layer. The lowest wear rate of PEB/C/N sample at 300 V is about 2.0375 × 10−6 mm3/ N·m, which is only 1/15 of the bare Q235 steel, the ternary hardening treatment shows a better wear resistance than the bare Q235 steel.
•Ternary hardening layers on Q235 Low-carbon steel was prepared by PEB/C/N.•Characterize structure and phase composition of PEB/C/N steel.•Microhardness and surface free energy were analyzed.•PEB/C/N process greatly improved corrosion and wear resistance of steel.
This study explores the influence of various parameters on bead profiles within the wire arc additive manufacturing (WAAM) process, specifically focusing on ER70S-6 low-carbon steel to produce ...thick-walled parts. The critical geometric characteristics under scrutiny are bead width (BW) and bead height (BH), with the primary goal being optimization. The research methodology incorporates the utilization of the Taguchi method, analysis of variance (ANOVA), regression modeling, and grey relational analysis (GRA) to scrutinize and enhance process parameters. The results reveal that a rise in wire feed speed (WFS) from 5 to 8 m/min and voltage (V) from 18 to 24 V leads to a substantial increase in BW, with contributions of 79.90% and 4.77%, respectively, according to ANOVA. Conversely, a rise in traverse speed (TS) from 0.3 to 0.6 m/min results in a reduction in BW by 11.90%, while the impact of gas flow rate (GFR) is relatively minor. Regarding BH, a rise in WFS within the 5-8 m/min range significantly enhances BH, with an ANOVA contribution of 17.78%. In contrast, higher voltage and TS lead to a reduction in BH, with TS exhibiting the dominant influence at 46.08%, followed by voltage at 31.13%, and WFS at 17.78%. The GFR exerts a negligible impact at 0.88%. To address the challenge of multi-objective optimization, GRA is proficiently employed, resulting in recommended process parameters for BW and BH: WFS = 8 m/min, V = 18 V, TS = 0.3 m/min, and GFR = 18 L/min. These results are robustly validated through experimental verification, affirming the accuracy of predictive models.
Nano Ni–Mo/graphene oxide (GO) sheet composites were successfully prepared by direct current electrodeposition with ultrasonic (WS) vibration on low-carbon steel. The composite coatings’s roughness, ...microhardness, corrosion and oxidation resistance, which were influenced by GO and ultrasonic factors, were investigated. Results from scanning electron microscopy (SEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) showed reduced graphene oxide (rGO) distributed in the coatings. X-ray diffraction patterns indicated that a decreased grain size of the nanocrystalline composite coatings after ultrasonic modification. In addition, results from thermogravimetric analysis from 25 °C to 600 °C showed that incorporating GO enhanced oxidation resistance. Best corrosion resistance value of 3.62 KΩ cm2 and 7.4 μA cm−2 of the ultrasonicated coatings (Ni–Mo/GO) were detected compared with coatings (Ni–Mo/GO) without sonic treatment or Ni–Mo coating.
•Ultrasonic-assisted electrodeposition can produce Ni-Mo/GO composite coatings.•GO nanosheets greatly affected the property of the Ni-Mo alloy coatings.•Proper ultrasonic vibration can improve the performance of composite coatings.
•A SAAM process was firstly carry out by using low-carbon steel in this work.•The toughness of SAAM product was vastly improved with barely loss of strength.•The intermediate zone of SAAM component ...possesses isotropic characteristics.•Unique intrinsic thermal cycle is the key factor in performance improvement.
Submerged arc additive manufacturing (SAAM) with high deposition efficiencies and unique cyclic re-heating was firstly introduced to fabricate the low-carbon steel product in this work. The microstructure and mechanical properties of the SAAM product was studied. The results showed that the intermediate zone of the as-deposited component was mainly composed of equiaxed α-Fe grains and possessing obvious homogeneous characteristics along the building direction. The impact energy of the component was vastly improved to over 300 J at −60 °C with little loss of strength. The tensile yielding strength ~346 MPa, elongation ~39% in vertical direction were competitive to that in horizontal direction, showing a fancy isotropic characteristic. The exclusive intrinsic heat treatment of SAAM holds the decisive role for this dramatic phenomenon.
•Steel passive films formed in concrete pore solution with red mud were investigated.•Detrimental impact of red mud on passivity of steels was highlighted.•Beneficial role of red mud in ...chloride-induced depassivation of steel was identified.
The influence of red mud (RM) on electrochemical behaviour, chemical composition, surface morphology and thickness of passive films naturally formed on low-carbon steel and 2304 stainless steel in alkaline concrete pore solutions was investigated using electrochemical measurements, XPS, AFM and SEM/EDS. Furthermore, chloride-induced pitting corrosion of passivated steels was characterized with and without RM. Results show that RM was detrimental to the passivity of steels by forming defective passive films with reduced thickness. Despite the formation of a less protective passive film on low-carbon steel, beneficial role of RM was highlighted in preventing chloride-induced depassivation and corrosion propagation.
