Protection of Metals and Physical Chemistry of Surfaces最新文献

A continuous cold drawing model of high-strength cold drawn pearlite steel wire with surface defects was established using finite element method, and the variation laws of V-shaped, concave, and U-shaped defects during the drawing process were explored. In addition, the influence of shape parameters and drawing process parameters on V-shaped defects was studied, which is of great significance for reducing the formation of defects in actual production. The results indicate that V-shaped defects are more easily eliminated during repeated drawing processes, while concave defects usually cannot disappear and eventually form folding defects, seriously affecting product quality. By adjusting the parameters of defect shape and drawing process, the disappearance of V-shaped defects can be promoted. Specifically, V-shaped defects with larger defect angles and smaller defect depths are easier to eliminate, while smaller drawing die angles and larger pass compression rates increase the uniformity of strain around the defect, which is beneficial for the disappearance of V-shaped defects.

This paper presents the results of studies of a combined process of plasma-photocatalytic destruction of aqueous solutions of Rhodamine B (RhB) with high concentrations (up to 40 mg/L) using two composite catalytic systems consisting of titanium dioxide fixed on zeolite NaX and diatomite granules. TiO₂ coating was applied by hydrothermal impregnation of carrier with solutions containing large-sized titanium hydroxocomplexes. The sorption and photocatalytic properties of impregnated granules were studied under static conditions. Contribution of sorption-catalytic processes to the efficiency of RhB decomposition was assessed in a plasma-chemical reactor of a dielectric barrier discharge. It was shown that the presence of both types of catalysts in the plasma leads to an increase in the rate of dye destruction by at least 20%. Maximum efficiency of decomposition in plasma is observed when using a TiO₂/zeolite catalyst and reaches 100% (2 g of catalyst in a reactor volume of 25 cm³ and a discharge power of 8.6 W/cm³) with a degree of mineralization of more than 80%, which indicates a high degree of oxidation processes.

In an attempt to improve the service life of components, Cu₅₀A1₂₅Zn₅Sn₂₀ series of high entropy alloy was fabricated liquid metallurgical route in various metal atomic distributions. The developed alloy series were subjected to various characterization performances. The corrosion test under 3.65 wt % NaCl solution was performed using linear sweep polarization method. The wear studies and microhardness response were achieved through CETR reciprocating sliding tribometer and an indenter Vickers hardness machine respectively. The Veeco technologically produced thermo-gravimetric analyzer was used for the temperature stability. The impact of the HEA structure modification was determined via scanning electron microscope (SEM) and X-ray diffractometer (XRD). From the results, it was observed that (Cu₅₀Al₃₅Zn₅Sn₁₀), (Cu₅₀Al₂₅Zn₅Sn₂₀), and (Cu₅₀Al₁₅Zn₁₀Sn₂₅) create better positive corrosion resistance response against the control sample with 0.9327 mm/year. (Cu₅₀Al₂₅Zn₅Sn₂₀) possessed more superior corrosion resistance compared to other samples, with the least CR and jcorr of 0.0423 mm/year and 4.240E–06 A/cm², respectively. The wear study also established that (Cu₅₀Al₂₅Zn₅Sn₂₀) sample possessed an exceptional counter wear response of 2.777E–06 mm³/N/m and 85.4 μm², respectively. In addition, (Cu₅₀Al₃₅Zn₅Sn₁₀) and (Cu₅₀Al₂₅Zn₅Sn₂₀) possessed the lower W_plast. values of 155 382.82 and 149 375.33 pJ, compared to the control sample with the highest W_elast., W_plast. and W_total value of 513 777.08, 1 156 098.06, and 1 669 875.14 pJ, respectively. The thermal stability of the (Cu₅₀Al₂₅Zn₅Sn₂₀) sample was observed between the temperature range of 500–690, 690–720, and 720–750°C. The structure image revealed the presence of few pores and homogeneous pattern. (Cu₅₀Al₂₅Zn₅Sn₂₀) sample was seen to have exhibited higher peak intensities and narrower peak widths with crystal phases of CuSn₂AlZn.

Electron beam welding is used for high precision welds mainly in aerospace industries. It is a type of fusion welding process in which a high beam of electrons hits the metals, produce heat and melts the base metals and then solidifies to form a weldment which is generally stronger than the individual base metals. This paper presents the corrosion testing of Electron beam welded pure copper and stainless steel 304 weldment. Tafel polarization technique is used to find the electrochemical corrosion behaviour of electron beam welded copper and SS304 dissimilar metal joints in NaCl saturated solution. The experiment was carried out using a CHI electrochemical workstation with a three-electrode setup where the welded specimen act as the working electrode. Tafel plots were generated to analyze the corrosion characteristics. An active-passive transition is found that indicates the formation of a protective oxide layer. The corrosion potential (E_corr) and corrosion current density (I_corr) of the weldments proves that the weldment has superior corrosion resistance when compared with the base metals. A significant increase in oxygen content and decrease in Fe, Cr, Ni and Cu concentrations are noted in the energy dispersive X-ray analysis (EDX) which indicates the metal degradation due to electrochemical reactions. Small corrosion pits are observed during the microstructural analysis proves the presence of pitting corrosion. However, the low I_corr values of the weldment is very low when compared with pure copper and SS304 which shows the enhanced corrosion resistance in the weldment due to microstructural refinement and alloying effects in the fusion zone. These findings prove that Cu-SS304 dissimilar weld using EBW is suitable for aerospace applications.

Efforts to produce environmentally friendly surface coatings with easy-to-clean qualities have gained momentum due to their ability to save water and chemicals while improving surface hygiene. nanopools of grafted lubricating layer for dewetting enablement (NP-GLIDE) coatings represent an innovative approach in surface engineering, combining nanoparticle technology with a unique polymer matrix. The present study focuses on the synthesis of bio-based NP-GLIDE coatings designed for easy-to-clean applications, with the goal of providing sustainable alternatives for a variety of sectors. In this work polyester-based coatings are formulated from itaconic acid as a bio-based resource, butane diol and it also contains H-polydimethylsiloxane (H-PDMS) as another diol to provide low surface energy. The synthesis procedure comprises grafting of PDMS onto a polyester chain by chemical pathways, further crosslinking with polyisocyanates resulting in coatings with tailored surface qualities that are easy to clean. The addition of PDMS in the polymer matrix helps in increasing the surface roughness and ultimately the hydrophobicity of the coatings. The synthesized resin and its coatings were examined using several analytical methods, including FTIR, NMR, DSC, TGA, SEM and contact angle. The contact angle study reveals the increase in contact angle from 56.68° of coating without PDMS to 105.25° of the coating with highest PDMS content. The SEM analysis also confirms the formation of nano-pools of PDMS which helps in creating a self-lubricating layer thus preventing adhesion of contaminants and facilitating their removal with minimal effort. The stain test showed that the coatings have good resistance to oil, inks and lipstick with the increase in content of PDMS. The cured coatings were further analyzed for general coating qualities in order to examine their performance properties.

In order to increase the service life of ductile iron (DI) components, various coating methods are used to improve surface properties such as hardness, wear resistance, and corrosion resistance. In recent years, the electrospark deposition (ESD) method has become a preferred surface coating process. This is due to its numerous advantages, including simple equipment and ease of use, strong metallurgical bonding, environmental friendliness, and cost-effectiveness. In this study, a high-entropy alloy was produced on unalloyed ductile iron using the ESD method at different voltages. The microstructures of the high-entropy alloy-coated ductile iron were examined, and properties such as micro hardness, layer thickness, and corrosion resistance were evaluated. To characterize the microstructure and composition of the coatings, optical microscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) analyses were performed. The results showed that the corrosion resistance of the Ductile iron coated with the high-entropy alloy increased. The best corrosion resistance and homogeneous coatings were obtained at upper voltages.

The present work focusses on the fabrication of new Ni–Co electrolyte for the development of Ni–Co electrocatalysts for water splitting application. All the Ni–Co alloy coatings were deposited from an acid sulphate bath and their electrocatalytic activity was tested in 1 M KOH. The Ni–Co alloys developed at range of current density from 3.0 to 6.0 A dm^–2 were found to be good electrode materials for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), as demonstrated by cyclic voltammetry (CV) and chronopotentiometry (CP) methods. The Ni–Co alloy deposits which are catalytically active for HER are found to be inactive for OER and vice versa. The change in surface appearance, composition, and the phase structure of all developed coatings were analysed using instrumental techniques like scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD), respectively.

Corrosion is one of the key technical problems impeding the widespread use of magnesium (Mg) and its alloys. Consequently, enhancing the corrosion resistance of Mg alloys is an urgent issue that necessitates immediate attention in their applications. Polytetrafluoroethylene (PTFE), often termed the ‘king of plastics’ because of its exceptional chemical inertness and non-reactivity, forms coatings that effectively shield metal substrates from corrosive environments. This capability substantially reduces corrosion rates, underscoring its considerable potential in corrosion prevention. In this study, PTFE coatings were successfully prepared on Mg–3Al–1Zn (AZ31) alloy sheets through electrophoretic deposition (EPD). The coatings underwent sintering treatments of varying durations, and their corrosion resistance properties were systematically evaluated. The results indicate that sintering duration critically influences the microstructural morphology of the PTFE coatings; extending the sintering duration within a specific range enhances the microstructure’s compactness. Furthermore, the study examined the corrosion behavior of Mg alloys coated with sintered PTFE in a 3.5 wt % NaCl solution, where the corrosion resistance of the sintered PTFE-coated AZ31 was significantly enhanced. Notably, coatings sintered for 14 h exhibited the highest corrosion resistance, with the corrosion current density decreasing from 4.05 × 10^–5 A cm^–2 for the bare AZ31 to 1.20 × 10^–7 A cm^–2 for the sintered PTFE-coated AZ31. Concurrently, the charge transfer resistance increased significantly from 227 to 2.72 × 10⁵ Ω cm². The coatings achieved a contact angle exceeding 123° and an adhesion rating of 5B. This offers a novel approach for mitigating corrosion in Mg and its alloys.

This study investigates the effect of an aluminized coating on the oxidation resistance of GH3039 superalloy. A powder embedding technique at 900°C with 60 wt % aluminum was employed to prepare the coating. The phase composition and surface morphology of oxidation products were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Untreated and aluminized samples were subjected to oxidation at 800, 900, and 1000°C for 100 h. Post-treatment, the GH3039 alloy exhibited a uniformly distributed aluminized layer about 90 μm thick. This layer comprised three distinct sub-layers: a top layer with Ni₂Al₃ and minor NiAl₃ phases, a middle layer of mainly Ni₂Al₃, and a β-NiAl phase-rich bottom layer. Oxide weight measurements indicated an initial rapid increase followed by a significant reduction at high temperatures, primarily due to Cr₂O₃ volatilization into gaseous CrO₃. Oxidation curves for the aluminized samples showed reduced and stable weight gain patterns, adhering mostly to the parabolic law with no further increase at advanced stages. The untreated samples presented a porous oxide film with complex components including Cr₂O₃, NiCr₂O₄, TiO₂, which adversely affected their oxidation resistance. In contrast, the aluminized samples predominantly displayed an Al₂O₃ film that transitioned from flaky θ-Al₂O₃ to a compact α-Al₂O₃ structure at increased temperatures, thereby significantly enhancing the alloy’s resistance against high-temperature oxidation.