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The surface of the steel after exposure to the corrosive salt-spray test; a sample C2; b sample C1c; c sample C1b, and d sample C1a
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Sol–gel boehmite coatings were produced on the polished surfaces of hypo-eutectoid C45carbon steel by dip coating. After the deposition the coatings were heat treated by drying at RT, 150 and 200 °C. It was found that for crack-free coatings, the drying temperature needs to be ≥150 °C. Properly heat-treated boehmite coatings then improve the corros...
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Citations
... However, decarburization is harmful to most steels, and the effect of ferrite decarburization is the worst [7]. Decarburization will reduce steel's surface hardness and fatigue strength and reduce its service life [8][9][10][11][12]. Carroll et al. [9] investigated the effect of decarburization on rolling contact fatigue and wear. ...
In order to understand the effects of heating temperature and holding time on decarburization of GCr15 bearing steel, an experimental device for heat treatment of bearing steel was designed and the sample was heated and held by a tubular heating furnace. The microstructure and depth of decarburized layer of bearing steel under various working conditions were observed and measured by a metallographic microscope. The results show that the total decarburization depth increases with the increase of temperature; almost no decarburization occurred below 700°C; ferrite decarburization occurred at 750°C; partial decarburization began to occur at 820°C; after 900°C, the decarburization layer is mainly partial decarburization. When the heating temperature is below 1000°C, the depth of total decarburization layer increases slowly and increases rapidly after 1000°C. The total depth of decarburization layer is directly proportional to the square root of holding time. The relationship between the depth of the total decarburization layer of bearing steel and the heating temperature and holding time in the annealing process was obtained.
... The C45E low-alloyed carbon steel (AISI/SAE1045) is a commercial low-cost material (80% cheaper than the SS304 and SS316L as common interconnect metals) commonly used due to its combination of formability and high strength. However, its low electrochemical properties that include degradation and rust resistance due to lack of chromium render it unpleasant to operate under harsh conditions [153,154]. As a result, several studies have been successfully performed to improve the C45E electrochemical weakness and use it as PEMFC interconnects under harsh conditions. ...
Proton Exchange Membrane Fuel Cell (PEMFC) is one of the promising technologies for generating electricity due to high energy density, environmental friendliness, and the absence of noise and pollution. However, under harsh acidic conditions, metal-based PEMFC interconnector (PEMFCMI) may induce degradation and gradual deterioration of the PEMFC stack leading to a decreased output voltage. Literature review shows that several types of stainless steel interconnect can be promising materials for commercial PEMFCs. Various surface modification techniques and different types of protective coatings have been applied on PEMFCMI. Although these surface modification methods and coatings improve resistance towards electrochemical degradation, still some weaknesses such as low electrical conductivity, stability, and high cost have limited their industrial viability. In this review, the PEMFC in general and the protective passive layers formed on interconnects in particular, have been discussed while keeping in view their electrochemical degradation mechanisms.
... The C45E carbon steel (AISI/SAE1045) is a commercial low-cost material (economic efficiency) commonly used due to its high strength and combination of formability that makes it easy to shape into sheets. However, several studies have been successfully performed to improve its electrochemical weakness such as corrosion resistance due to lack of chromium deficiency to operate under harsh conditions [44]. Our previous study has shown that TiO 2 -SiO 2 TFSOC and its combination with C45E iron oxides after heat treatment process have successfully served as high physical and electrochemical protective barriers (61 kΩ cm 2 compare to the 2 kΩ cm 2 as polarization resistance for the bare C45E steel) against corrosive attacks [38]. ...
High cost and low electrochemical stability of the interconnection in Proton Exchange Membrane Fuel Cell (PEMFC) in the presence of H2SO4 are one of the main issues hindering the commercialization of these devices. This manuscript presents the utilization of cost-effective steel in an attempt to minimize the PEMFC interconnection costs with a thin-film solid oxide coating (TFSOC) providing sufficient corrosion resistance for efficient long-term operation. Novel Ti0.50-y/2Si0.50-y/2Nby1,2O2 as TFSOC was deposited on the C45E steel as a metal interconnect utilizing a sol-gel process at various annealing temperatures. The analysis of the phase and surface morphology demonstrates that lower annealing temperatures developed nanometric crystallite size of 68 nm, more uniform structure and higher corrosion resistance. Under standard test conditions, the TFSOC demonstrated high polarization resistance (1.3 kΩ cm2) even after 720 hours (h). Electrical conductivity of the TFSOC as low as 1.4 × 10-2 (Ω m)-1 and activation energy of 0.20 eV were achieved, which helps to maintain the PEMFC output power.
... This method has the advantages of low costs, simple operation, and low reaction temperature. Dense and porous film can be obtained from this technology, which can prolong the service life and enlarge the application of Al alloys in the marine environment [22][23][24][25][26][27][28]. Salazar-Hernández et al. presented the DBTL behavior in alkylalkoxisilane condensation as anticorrosive coatings in Al-6061 for aerospace applications. ...
Given their outstanding versatile properties, multilayered anticorrosion coatings have drawn great interest from researchers in the academic and engineering fields. However, the application of multilayered coatings is restricted by some limitations such as low interlayer compatibilities, the harsh preparation process, etc. This work introduced a composite film fabricated on a 2A12 aluminum alloy surface, including an anodic oxide film, a sol–gel film, and a layer-by-layer (LBL) self-assembling film from bottom to top. The microstructure and elemental characterization indicated that the finish of the coating with the LBL film resulted in a closely connected multilayered coating with a smoother surface. The anticorrosion performance was systematically evaluated in the simulated corrosive medium and neutral salt spray environment. The integrated coating with the LBL film presented an excellent anticorrosion ability with system impedance over 108 Ω·cm2 and a self-corrosion current density two orders of magnitude lower than that of the other coatings. After the acceleration test in a salt spray environment, the multilayered coatings could still show a good protective performance with almost no cracks and no penetration of chloride ions. It is believed that the as-constructed multilayered coating with high corrosive properties and a fine surface state will have promising applications in the field of anticorrosion engineering.
... The prepared AS was dried at 100°C and put into a muffle furnace for 1 h at 200, 400, 600, and 800°C. Figure 8 shows the XRD spectrum of AS under ablation for 1 h at different temperatures, revealing that as temperature increased, the diffraction peak of boehmite (AlOOH) increased and narrowed at 100 and 200°C [35]. The crystallization increased to some extent because the water in the sample gradually evaporated after being heated. ...
The extrusion impregnation method is used to prepare carbon fiber felt/portland cement (CFF/PC) composite materials. The samples are placed into muffle furnace for ablation, but carbon fiber is oxidized at around 450 °C. To improve the oxidation resistance of carbon fiber, Al2O3 sol–gel (AS) is prepared to coat the surface of carbon fiber. The extrusion impregnation method is also used to prepare AS–CFF/PC composite materials. The samples are also ablated into muffle furnace at different temperatures. The results indicate that carbon fiber is uniformly dispersed and closely arranged in the matrix, presenting a three-dimensional network distribution. The bending and compressive strengths of CFF/PC composite materials are increased by 200% and 12% when compared with that of PC material at room temperature. The AS coating layer can effectively improve the antioxidant capacity of carbon fiber at high temperatures. The comparison reveals that AS–CFF/PC composite materials exhibit improved high-temperature resistance performance.
To study the kinetics of decarburization under a weakly oxidizing Ar-H2O-H2 atmosphere, the decarburization process was analyzed with strips of different thicknesses (2, 1.5, 1 mm). A Fe-C alloy strip (approximately 4.15 wt.% C) was placed in the heating field and heated to the set temperature of 1413 K. The decarburization processes for strips with different thicknesses were analyzed. Decarburization of the 2-mm-thick strip was divided into three stages, and the decarburization processes of the 1.5-mm-thick and 1-mm-thick strips were divided into two stages. At different stages, the rate controlling step changed. The entire decarburization reaction was carried out in stages. The steps restricting strip decarburization mainly included carbon diffusion, carbon-rich phase decomposition, and possible mixed (multistep) mechanisms. Surface decarburization reactions were most likely to have a significant impact at the onset of decarburization. Dissolution of the carbon-rich phase ran through the whole process of decarburization, but it should be reflected in the middle and late stages. In the early stage of decarburization, an increase in the PH2O/PH2 ratio accelerated the decarburization reaction rate and improved the decarburization effect.
A hybrid sol–gel coating was synthesized by mixing tetraethylorthosilicate and triethoxyvinylsilane to protect St37 steel in 3.5 wt.% NaCl solution. The prepared coating was characterized using Fourier transform infrared spectroscopy, x-ray diffraction, and scanning electron microscopy. To improve the protection ability of the proposed coating, two pigments, including bromophenol blue and eosin-methylene blue, were added to the coating as corrosion inhibitors. The influence of multi-walled carbon nanotube as the surface modifier on the performance of the coating was also investigated. Corrosion tests were performed by electrochemical impedance spectroscopy. The results obtained indicated that the presence of each of the inhibitors in the coating resulted in a slight improvement in corrosion protection. However, the simultaneous addition of the nanoparticle and inhibitor into the coating made a significant increase in the corrosion resistance of the coating.
TiO2–SiO2 multilayer protective coatings were prepared via the sol-gel method on a C45E steel substrate. The influences of the number of layers, annealing temperature and annealing atmosphere on the corrosion resistance were investigated. Electrochemical characterization showed correlations between the processing parameters and the corrosion resistance. A maximum polarization resistance of 61 kΩ cm² was achieved with coatings of three layers annealed at 900 °C in air compared to just 2 kΩ cm² for the uncoated C45E steel sample. This research revealed the possibility of preparing a dense corrosion-resistant layer on C45E steel with minimal surface defects by optimizing the processing parameters.
Given their outstanding versatile properties, multilayered anticorrosion coatings have drawn great interest from researchers in the academic and engineering fields. However, the application of multilayered coatings is restricted by some limitations such as low interlayer compatibilities, the harsh preparation process, etc. This work introduced a composite film fabricated on a 2A12 aluminum alloy surface, including an anodic oxide film, a sol-gel film, and a layer-by-layer (LBL) self-assembling film from bottom to top. The microstructure and elemental characterization indicated that the finish of the coating with the LBL film resulted in a closely connected multilayered coating with a smoother surface. The anticorrosion performance was systematically evaluated in the simulated corrosive medium and neutral salt spray environment. The integrated coating with the LBL film presented an excellent anticorrosion ability with system impedance over 10 8 Ω·cm 2 and a self-corrosion current density two orders of magnitude lower than that of the other coatings. After the acceleration test in a salt spray environment, the multilayered coatings could still show a good protective performance with almost no cracks and no penetration of chloride ions. It is believed that the as-constructed multilayered coating with high corrosive properties and a fine surface state will have promising applications in the field of anticorrosion engineering.
Unwanted removal of carbon from surface may occur during laser surface processing of steels despite the short interaction time and thermal cycle. However, no attention is paid in literature to investigate this phenomenon systematically. This paper presents two different scenarios during laser surface processing of steels: complete absence of decarburization for an alloy steel but decarburization with depth up to 70 µm for a plain carbon steel, showing that alloying elements tend to retard decarburization process by reducing the mobility of carbon in austenite. Further analysis reveals that the laser-induced decarburization is dependent primarily on peak temperature and austenitization kinetics.
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