Coated Steel Specimens Research Articles

Structural strain and crack monitoring based on the fluorescence response of graphene quantum dots

Graphene quantum dots (GQDs), a novel nanomaterial, offer new avenues for structural health monitoring owing to the remarkable fluorescence response. In this study, the GQDs-epoxy resin composites were fabricated and applied to structural surface. Tests including tension, compression, bending, and fatigue were conducted to explore the fluorescence response of composites to structural strain and cracks. Results show that composites exhibited a heightened fluorescence sensitivity to structural strain. During the tensile tests of coated steel specimens, the fluorescence intensity of composites exhibited positive and negative correlation responses with increasing strain. Whereas in the compression test of coated concrete specimens, solely increased fluorescence intensity with rising strain was observed. Composites demonstrated excellent crack characterization on concrete and steel structures, whether penetrating or developing cracks. The fluorescence response of composites to cracks was based on the fluorescence enhancement at the crack site, and fluorescence intensity was approximately inversely proportional to crack width.

Highly scalable synthesis of MoS2 thin films for carbon steel coatings: influence of synthetic route on the nanostructure and corrosion performance

Due to its numerous potential applications, molybdenum disulfide (MoS2; moly), one of the newly developing transition metals dichalcogenides (TMDCs), has exceptionally drawn high interest. Particularly in solution-based applications, MoS2 has potential that has not yet been completely realized. The structural and morphological characteristics of MoS2 films prepared by two diverse approaches for example chemical vapor deposition (moly/CVD) and autoclave (moly/AC) methods were investigated by scanning electron microscopy supported by energy dispersive X-ray spectroscopy (SEM/EDX), FTIR, transmission scanning microscopy (TEM) and X-ray diffraction (XRD). The anti-corrosive performance of the uncoated and coated steel was investigated in 1.0 M HCl. Electrochemical tools such as electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) were completed to measure the corrosion protection properties. The moly/CVD and moly/AC coated 5-layer steel substrates showed a protection capability of 94.2 and 98.2%, respectively. The effect of the synthetic strategy and the film thickness on the corrosion characteristics was examined. Before and after exposure to the corrosive solution, the surface morphology of the uncoated and coated steel specimens was described using SEM. These MoS2 thin films are a new and cost-effective alternative to improve steel corrosion resistance and could be used to protect steel in environments with chloride acidic medium due to their unique physicochemical properties.

Characterization of steel lined with multilayer micro/nano-polymeric composites

This work studied comparison of the mechanical and barrier resistance properties between different structures of three multilayers polymeric coating on each side of the steel coupons. Epoxy filled with 1 wt%, 2 wt%, and 3 wt% micron or nano-sized alumina (Al2O3) particles represented the coating layers to steel on both sides. Barrier resistance was performed by immersing the coated steel specimens in salt solution and in a citric acid medium. Adding alumina (Al2O3) particles in micron and nano size to epoxy coatings improved the barrier resistance, tensile, and hardness under dry and wet conditions as compared to pure epoxy coating. Further increases in Al2O3 micro/nanoparticles cause deterioration in tensile strength and barrier resistance. The steel lined with epoxy filled with 1 wt% Al2O3 nanoparticles has a maximum tensile strength of 299.5 MPa and 280.9 MPa under dry and wet conditions, respectively. However, the steel lined with epoxy filled with 1 wt% Al2O3 microparticles has a tensile strength of 296.5 MPa and 275.4 MPa under dry and wet conditions, respectively. Good properties were observed with stepwise graded micro/nanocomposite coatings. The steel lined with epoxy filled with 3 wt% Al2O3 nanoparticles has maximum hardness of 46 HV and 40 HV under dry and wet conditions, respectively.

Microstructure and properties of YSZ-Al2O3 functional ceramic thermal barrier coatings for military applications

Current study renders its focus on the investigation of functionally graded Yttria Stabilized Zirconia (YSZ) and alumina (Al2O3) thermal barrier coatings (TBC) deposited on EN steel substrates used in gun barrel through atmospheric plasma spray (APS) process. A bond coat and the top coats was made with two distinct compositions using YSZ-Al2O3 in 75:25 and 50:50 weight ratio through APS process with two carrier gas concentrations of 3 and 4 standard cubic feet per hour (scfh). Coatings were characterized with thermal testing, X-ray Diffraction (XRD) and Field Emission Scanning Electron Microscope examination (FESEM). Surface roughness test, wear and scratch test of the uncoated and coated steel specimens was also measured. YSZ-Al2O3 coated EN36C steel possessed greater insulation performance under a carrier gas flow rate of 3scfh compared to all other specimens. EN36C steel coated with YSZ-Al2O3 in the ratio of 75:25 has better wear and scratch resistance indicating lesser deformation compared to other materials.

The effect of superhydrophobic surface topography on underwater corrosion resistance of steel

This article describes the study of the topography effect of superhydrophobic surfaces on the corrosion protection performance of steel through the air plastron behavior when subjected to an underwater environment. A random superhydrophobic surface was fabricated using spray coating and characterized for morphology and wettability by scanning electron microscopy (SEM) and goniometer measurements, respectively. By comparing the coated surfaces both with and without air plastron, it was found that superhydrophobicity postponed the corrosion of the coated steel specimens. This increase in corrosion protection of the superhydrophobic surface was due to the air plastron created by the superhydrophobicity in underwater immersion. Since different areas showed differing air plastron lifetimes (wetting behavior), it was assumed that the underlying topography of the superhydrophobic coating controlled the air plastron lifetime. To investigate this behavior, the micron scale topography of the different areas was studied using the technique of laser confocal microscopy over the specific areas and correlating with air plastron lifetime. Using the theoretical analysis based on superhydrophobic robustness and assuming the solid fraction is the same for different locations, it was demonstrated that the feature size [extracted by roughness analysis as root-mean-square (RMS)] correlated with the air plastron lifetime. It was confirmed from the plot of RMS and air plastron lifetime that smaller feature sizes could extend the air plastron lifetime and provide better anticorrosion performance.

Determination of specific wear rate of steel coated with tungsten carbide using Taguchi technique for textile applications

Textile industry is one of the promising industries in India. Textile machineries have a huge number of components that are subject to wear and tear. Replacement of the components is very expensive and may not produce break even in many cases. Coatings have been widely used on the mechanical components that are being used in the textile machinery. In this work, the wear characteristics of tungsten carbide coated steel specimens have been studied for probable application in the textile industry. For the purpose of coating, different coating techniques have been studied, among that HVOF technique and plasma coating technique have been extensively studied. In this work, plasma coating technique was used to coat the EN 8 steel specimens with tungsten carbide. The coatings were of varying thickness and different stand-off distance of the plasma torch was considered for the coating to see which would be the best coating thickness and the best stand-off distance. Using the pin on disc experimental set up, the specific wear rate was calculated and the friction coefficient was calculated. It was observed that the frictional force and the Co-efficient were the least in the case of the first experiment that is, at 4 in. stand-off distance and 100 µm coating thickness. SEM analysis and XRD analysis were done on the specimens for mechanical characterization and to ensure that the coatings are uniform and also to determine the composition of the coating.

Simplified approach to assess water uptake in protective organic coatings by parallel plate capacitor method

Water uptake in organic coatings is often determined from changes in coating capacitance obtained by analyzing electrochemical impedance spectroscopy (EIS) data. However, the method has been criticized for providing inconsistent results poorly correlating to gravimetry measurements, which may arise from the absence of a straightforward approach to treat impedance data. A simple method based on forming a parallel plate capacitor (PPC) and measuring the capacitance using commercial inductance (L), capacitance (C) and resistance (R) meter is proposed. Water content in commercial coil coated steel specimens was determined by the Brasher-Kingsbury equation from coating capacitance measured by both PPC and EIS methods. A good correlation was observed between the reference gravimetric results and water uptake measured by the PPC approach. The new method can be considered as an industrial technique applicable also for on-site determination of water content in protective coatings applied on metallic structures.

Designing of phosphorous based highly functional dendrimeric macromolecular resin as an effective coating material for carbon steel in NaCl: Computational and experimental studies

AbstractObjective of this study is to develop a highly effective and durable phosphorus based epoxy resin as anticorrosive coating material for carbon steel in 3% NaCl medium. The hexaglycidyl N,N′,N″‐tris (4,4′‐ethylene dianiline) phosphoramide (HGTEDPA) was characterized using spectral methods. The anticorrosive formulation (HGTEDPA‐MDA) was synthesized using HGTEDPA curing with 4,4′‐methylenedianiline (MDA). The formulation (HGTEDPA‐MDA) coated steel specimens were exposed to UV radiation for a specific durable (189 days) and durability of the formulation was tested along with its inhibition effectiveness. The anticorrosive property of the formulation was evaluated using electrochemical (electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP)) methods. Results showed that HGTEDPA‐MDA coating improved the corrosion resistance value even after exposing 180 days to the UV radiation. PDP study suggested that HGTEDPA‐MDA before and after UV radiations acted as mainly anodic and cathodic type of inhibitor, respectively. The EIS and PDP results were corroborated with density functional theory (DFT) and molecular dynamic simulations (MDS) methods and a reasonable good agreement was observed. DFT study revealed that HGTEDPA‐MDA interacts with the metallic surface using donor–acceptor interactions. MDS study revealed that HGTEDPA‐MDA spontaneously interacts with steel surface and adsorb using horizontal orientation.

Evaluations of Hot Corrosion Behavior of Al<sub>2</sub>O<sub>3</sub> Thermal Spray Coatings with ZrO<sub>2</sub> Reinforcements on T-91 Steel

Different coating with varying quantities of Al2O3 and ZrO2 were fabricated on the SA213 T-91 steel using plasma spray method to study hot corrosion resistance behavior. Experiment was conducted under the molten salt environment of 60% Na2SO4-40%V2O5 at a temperature of 900℃ inside a furnace for 50 cycles. Each cycle consisted of 1hr heating and 20 min cooling at room temperature. Results were examined using the visual inspection, weight change measurement, X-ray diffraction technique and Scanning Electron Microscopy/ Energy Dispersive X-Ray Spectroscopy (SEM/ EDS) analysis. Results showed that uncoated T-91 steel was more prone to hot corrosion as compared to coated steel specimens. It was noticed that ZrO2 reinforcements in Al2O3 coating matrix helped to enhance corrosion resistance of these coatings. The corrosion resistance increased with increase in ZrO2 content in coating matrix.

Improving the hot corrosion resistance of boiler tube steels by detonation gun sprayed coatings in actual boiler of thermal power plant

PurposeThis paper aims to investigate the hot corrosion behavior of Ni-Cr and Cr3C2-NiCr coatings, deposited on T11, P91 boiler steels by detonation gun spray coating (D-Gun) process to enhance high temperature corrosion resistance.Design/methodology/approachHot corrosion studies were conducted in secondary super heater zone of boiler at 900 °C for 10 cycles on bare and D-Gun coated steel specimens. The microhardness and porosity values of as-sprayed coatings were measured before exposing the specimens in the boiler environment. Each cycle consisted 100 h of heating in the boiler environment followed by 20 min of cooling in air. The weight change measurements were performed after each cycle to establish the kinetics of corrosion using thermogravimetric technique. X-ray diffraction, SEM techniques were used to analyze the corroded specimens.FindingsUncoated boiler steel experienced higher weight loss. The Cr3C2-NiCr coating was found to be more protective than Ni-Cr coating. The phases revealed the formation of oxide scale on coated specimens, mainly consist of nickel and chromium, which are reported to be protective against the hot corrosion.Originality/valueThere is very limited reported literature on hot corrosion behavior of Ni-Cr and Cr3C2-NiCr coatings deposited on the T11 and P91 substrates by detonation gun (D-gun) spray technique. T11 and P91 alloy steels have been chosen for this study because these two alloys are used to manufacture boiler tubes used in Indian thermal power plants.

Phosphorous-based epoxy resin composition as an effective anticorrosive coating for steel

Epoxy resin (ER) is an attractive material for metal protection against corrosion; it can form a strongly adhered film onto a metal surface through its multi coordination sites. In this study, an epoxy resin-based formulation was designed, prepared, and applied onto steel surface with and without a pigment. The anticorrosive formulation (ER–MDA–ZP) was prepared from the ER and the hardener 4,4′-methylene dianiline (MDA) in the presence of the anticorrosive pigment zinc phosphate (ZP). A second standard formulation (ER–MDA) was prepared without ZP. The epoxy and the hardener react to form a 3D cross-linked polymeric network with multicoordination sites (hydroxyl and amino groups) for metals. The characterization of the epoxy resin was performed using Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (1H and 31P NMR). Both samples exhibited excellent thermal properties as they subjected to thermal analysis using differential scanning calorimetry. The ER–MDA–ZP formulation showed a higher glass transition temperature (Tg) than ER–MDA. The coated steel specimens were immersed for 1 h in a 3 wt% NaCl solution and their anticorrosive properties were monitored by electrochemical impedance spectroscopy (EIS). The total resistance (Rt) values obtained by the EIS method for the ER–MDA and ER–MDA–ZP formulations were 21,383 Ω cm2 and 55,143 Ω cm2, respectively. The coated steel samples after the acid treatment were subjected to aging by exposing them to a UV light for 2000 h. The aging caused the Rt values to drop to 1621 Ω cm2 and 7264 Ω cm2, respectively. The results indicate the formation of a highly stable film of ER–MDA–ZP formulation on the steel surface that withstands an accelerated corrosive environment of 2000 h exposure to UV light and 1 h of immersion in a 3 wt% NaCl.

Tensile and bend behaviour of nanostructured HVOF and flame sprayed stellite coatings

Stellite 6 powder (CoCrSiW) was deposited using flame spray (FS) and high velocity oxygen fuel (HVOF) techniques on steel substrates. The microstructure of stellite coatings produced with these deposition techniques displayed a rather similar morphology consisting of cobalt-rich dendrites surrounded by hard (Cr3C7) carbide particles. The stellite (both FS and HVOF) coating was found to reduce the tensile strength of the steel. The failure of the coated steel specimens initiated by cracking on the coating surface, transverse propagation of the cracks towards the coating - substrate interface and diversion along the interface leading to local delamination and breakage. During the bend tests cracks developed along the coating and the main failure in the coating occurred due to the tensile-shear deformation, particularly in the coating-substrate material interface. The coating thickness does not appear to affect the bending strength. During bending the number of surface cracks per unit length decreased with increasing coating thickness. Stereoscopic analysis showed that the thicker the coating the deeper the surface cracks. When the critical stress for crack propagation reached defect sites at the substratecoating interface, the entire coating failed and peeled off from the substrate.

Smart acrylic coatings for corrosion detection

Corrosion detecting coating was prepared using acrylic polymer chemically modified with 5-acrylamido-1,10-phenanthroline (AMP). Modified polymers having varied AMP content were synthesized and characterized by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, differential scanning calorimetric (DSC) and thermo gravimetric (TGA) analysis. The modified polymer after complex formation with Fe2+ ions showed additional absorption peak at 359 nm in UV–vis spectrum confirming the polymer-Fe (II) complex formation. Corrosion sensing ability of these polymers was evaluated by immersing the coated mild steel panels in 3.5% NaCl solution and visually monitoring the color change of coating. Electrochemical impedance spectroscopy (EIS) was used to measure the polarization resistance (RPR) of coated steel specimens and correlated with the color change of coating. Coating from the point of color change was removed and bare metal was analyzed by scanning electron microscopy (SEM) to reconfirm that the point of color change was the corrosion site. Results reveal that these new sets of polymers can be used for corrosion detection.

Long-term corrosion protection of arc spray Zn-Al-Si coating system in dilute chloride solutions and sulfate solutions

In order to study the corrosion protective mechanism of arc spray Zn-Al-Si coating system in soil environment, carbon steel specimens covered with arc spray Zn-Al-Si coating system were immersed in dilute chloride solutions and sulfate solutions for over 500 days, and the corrosion behavior of the coated steel specimens was examined. The evolution of the open-circuit potential (OCP) of the immersed specimens and the anodic polarization curves of the arc spraying Zn-Al-Si layer were investigated. The corrosion products were characterized and the local polarizations at the cross-shaped scratch were performed after immersion test. The results showed that red rust of steel occurred in sulfate solutions but was inhibited in chloride solutions. The OCP of specimens increased with immersion time due to depressed anodic reaction. The corrosion products of arc spraying Zn-Al-Si layer were mainly Zn(OH)2, ZnO and Zn5(OH)6(CO3)2 in sulfate solutions, and Zn5(OH)6(CO3)2 and layered double hydroxide Zn0.70Al0.30(OH)2(CO3)0.15·xH2O in chloride solutions. Long-term corrosion protection of arc spray Zn-Al-Si coating system in chloride solutions is attributed to the formation of Zn0.70Al0.30(OH)2(CO3)0.15·xH2O and absence of ZnO.

Investigation of anti-corrosive properties of poly(aniline-co-2-pyridylamine-co-2,3-xylidine) and its nanocomposite poly(aniline-co-2-pyridylamine-co-2,3-xylidine)/ZnO on mild steel in 0.1 M HCl

A soluble terpolymer of aniline (AN), 2-pyridylamine (PA) and 2,3-xylidine (XY), poly(AN-co-PA-co-XY) and its nanocomposite with ZnO nanoparticles namely, poly(AN-co-PA-co-XY)/ZnO were synthesized by chemical oxidative polymerization employing ammonium persulfate as an oxidant. Nanocomposites of homopolymers, polyaniline/ZnO, poly(XY)/ZnO and poly(PA)/ZnO were also synthesized by following similar synthesis route. FTIR, XRD and SEM techniques were used to characterize the synthesized compounds. The synthesized compounds were chemically deposited on mild steel specimens by solvent evaporation method using N-methyl-2-pyrrolidone (NMP) as solvent and 10% epoxy resin (by weight) as binder. Anticorrosive properties of homopolymer nanocomposites, terpolymer and its nanocomposite coatings were studied in 0.1M HCl by subjecting them to various corrosion tests which includes: free corrosion potential measurement (OCP), weight loss measurements, potentiodynamic polarization, and AC impedance technique. The surface morphology of the corroded and uncorroded coated steel specimens was evaluated using SEM. The corrosion protection performance of terpolymer nanocomposite coating was compared to the terpolymer and individual homopolymers nanocomposites coatings after 30 days immersion in corrosive medium.

G0300902 レーザ熱処理によるセラミックス被覆鋼の転がり疲労はく離発生寿命の向上化に関する研究

In order to investigate the effects of new surface modification method "Laser quenching after coating" on the rolling contact fatigue strength of ceramic coated steels, CrAIN coated steel specimens and TiAIN coated steel specimens were processed by this method and the thrust type rolling contact fatigue tests were carried out for these specimens. In the process of the laser quenching after coating, laser irradiation was carried out under various laser power conditions. The delamination initiation life of CrAIN coated specimen increased with the heat input, however the excessive heat input decreased the delamination initiation life. The adhesive strength of CrAIN coated specimen showed similar variation for the increase of the heat input, and a good correlation was recognized between the delamination initiation life and the adhesive strength. It was considered that the delamination initiation life of CrAIN coated specimen was strongly affected by the adhesive strength. For TiAIN coated specimen, the delamination initiation life once increased and then decreased with increasing the heat input, although the adhesive strength increased monotonously. The hardness of TiAlN film decreased from the heat input at which the delamination initiation life began to decrease. By laser irradiation, the film hardness of TiAIN decreased more easily than that of CrAIN, because the oxidation temperature of TiAIN was lower than CrAIN. The decrease of the delamination initiation life of TiAIN coated specimen laser-irradiated under the high heat input condition could be explained by the decrease of the film hardness. The delamination initiation life of TiAIN coated specimen was strongly affected by the decrease of the film hardness caused by laser irradiation.

Delamination initiation life and growth behaviour of ceramic coated steels quenched after coating process under rolling contact loading condition

In order to investigate the effects of a new surface modification method, ‘the substrate quenching after coating’ on the rolling contact fatigue strength, TiN coated steel specimens and CrAlN coated steel specimens were processed by this method and the thrust type rolling contact fatigue tests were carried out for these specimens. In the process of the substrate quenching after coating, two types of quenching methods, furnace quenching and laser quenching, were used.For the furnace quenched specimens, the delamination initiation life of CrAlN coated specimen was longer than that of TiN coated specimen. This reason could be explained by the difference of the oxidisation of CrAlN and TiN in their furnace quenching process. For CrAlN coated specimens, the delamination initiation life of the laser quenched specimens was longer than that of the furnace quenched specimens. After the initiation, the delamination of the furnace quenched specimen grew much faster than that of laser quenched specimen. These reasons could be explained by the difference of the process time of the furnace quenching and the laser quenching. The process time, in which the ceramic coating of the specimen was exposed to an elevated temperature, of the furnace quenching was much longer than that of laser quenching.It is considered that substrate laser quenching after coating could be an effective way to improve the delamination initiation life and to reduce the delamination growth rate under rolling contact fatigue.

Cracking Behavior of Al-Si Coating on Hot Stamping Boron Steel Sheet

Cracking behavior of Al-Si coating on hot stamping boron steel was investigated under different hot deformation conditions. The Al-Si coated steel specimens were isothermally deformed under applied tensile strain by Gleeble 3500, at 700, 750, and 800 oC with a strain rate of 0.1/s. Morphology of the coating was observed through scanning electron microscopy and optical microscopy. The results indicate that microcracks appear during the austenitizing treatment, because of thermal expansion mismatch of the Fe-Al-Si intermetallics. Under applied tensile strain, the cracks propagate along the direction perpendicular to the coating/substrate interface. When these cracks reach the interface, the surface coating layer is divided into segments by through-thickness cracks. With increasing deformation temperature, the crack density tends to be smaller, while the cracks are wider. It is suggested that with a higher deformation temperature, the Al-Si coated boron steel could withstand more deformation before the steel substrate is exposed.

A Comparative Study on the Corrosion Behaviour of Gas Nitrided and TiAlN Coated AISI D2 Steel by Thermo-Reactive Diffusion Technique

In this study, the corrosion behaviors of nitride and titanium aluminum nitride (TiAlN) layers deposited on AISI D2 steel samples are reported. Steel was at rst nitrided in a nitrogen and ammonia atmosphere at 575 ◦C for 8 h and then titanium nitride coating treatment was performed in the powder mixture consisting of ferro-titanium, aluminum, ammonium chloride and alumina at 1000 ◦C for 2 h by thermo-reactive di usion technique. Phase analysis and corrosion tests were realized on the titanium aluminum nitride coated steel. The corrosion properties of uncoated and coated samples were characterized by potentiostatic polarization test. The tests were conducted using a three-electrode system test unit with a platinum counter electrode of 2.269 cm and an Ag/AgCl, 3 M KCl electrode as the reference electrode. Nitrided and TiAlN coated steel specimens exhibited higher corrosion resistance than uncoated steel in 0.5 M H2SO4 solution. Conclusively, the application of nitride and TiAlN lms on AISI D2 steel increased surface hardness and corrosion resistance. TiAlN coating exhibits the highest corrosion resistance.

The influence of hydrogenated amorphous carbon coatings (a-C:H) on the fatigue life of coated steel specimens

The influence of a hydrogenated amorphous carbon coating on the fatigue life of an austenitic steel was evaluated in this work. The fatigue damage mechanisms have been compared for both coated and uncoated specimens. A strong increase in fatigue life of more than 300% for low total strain amplitudes was found for the coated specimens. The influence of the coating on the fatigue life increases with decreasing total strain amplitude. The damage mechanisms were analyzed using atomic force microscopy and focus ion beam cross sectioning. The coated specimens show a significantly reduced surface roughening. Slip bands in the steel sample could not penetrate the coating and thus slip step formation on the surface was avoided, leading to the enhanced fatigue life. The compressive residual stress in the coating is discussed being the main reason for the enhanced fatigue life of the specimens.