In this research, Zn-6%Mg-x%Al (x = 15∼22) coatings were prepared using a laboratory-scale simulator. Their properties were characterized by NSS tests, electrochemical measurements, microstructural analysis, and SKPFM. The NSS test data revealed that the corrosion resistance of the Zn-6%Mg-x%Al coatings did not improve continuously with increase aluminum content. The Zn-6%Mg-19%Al coating exhibited the best corrosion resistance, showing no red rust after 2400 h of testing. To further identify the coating with the optimal corrosion resistance, electrochemical measurements were performed on four selected coatings. The results showed that Zn-6%Mg-19%Al coating exhibited the lowest corrosion current density (915 μA/cm 2 ). While previous studies have primarily focused on corrosion products, the key distinction of this work is that it elucidates the corrosion mechanism from the perspective of microstructural constituency. Microstructural analysis revealed that the dendrites consist of an α-Al core and a shell of Zn-Al eutectoid microstructure. The volume fraction of this core-shell dendritic structure was found to determine the corrosion resistance of the Zn-6%Mg-x%Al coatings. SKPFM measurements demonstrated that the Volta potential of α-Al phase in the dendritic core was −567 mV, which is higher than that of Zn (−653 mV). In contrast, the Zn-Al eutectoid structure in the dendritic shell exhibited the lowest Volta potential of −711 mV. The Zn-6%Mg-19%Al coating achieves its optimal corrosion resistance by balancing the area ratios of the α-Al dendritic core and the Zn-Al eutectoid shell.

Molybdenum-titanium-zirconium (TZM) alloy, renowned for its high refractory properties, has limited applications in open atmospheres because of its low resistance to oxidation at elevated temperatures. In this study, Ni-Al 2 O 3 cold spray coating was employed to create a protective layer on the TZM to protect against high-temperature oxidation. The microstructure, microhardness, and oxidation performance of the Ni-based MMC coating were investigated at various temperatures up to 1000 °C. The MMC coating's microstructure consisted of Al 2 O 3 particles randomly distributed within the nickel matrix, resulting from the CS coating, which is a solid-state deposition method. In the oxidation tests of TZM at temperatures of 750 and 1000 °C, it was observed that there was a significant mass loss because of the generation and evaporation of the MoO 3 phase. It was determined that the Ni-based MMC coating on TZM significantly reduced mass loss by preventing molybdenum from coming into contact with oxygen. Following the 1000 °C oxidation test, the XRD examination revealed the presence of MoO 2 and MoO 3 phases on the surfaces of TZM, while NiO and NiMoO 4 phases were identified on the surfaces of the MMC coating. It was determined that the NiMoO 4 phase formed at the end of the MoO 3 vapor on the TZM side surfaces, while the NiO phases developed in the MMC coating layer through a chemical reaction.

This study fabricated two composite anticorrosion coatings based on a waterborne epoxy resin matrix, incorporating TC4 alloy powder and TiO 2 nanoparticles, respectively, with mineral powder hybridization to enhance performance and reduce material costs. Salt spray testing demonstrated that both systems maintained stability in corrosive environments for over 30 days. However, the TC4-based coating exhibited local edge warping on day 10, indicative of insufficient interfacial adhesion and structural instability. In contrast, the TiO 2 composite coating retained structural integrity throughout the test period, demonstrating superior corrosion resistance. Characterization analyses (SEM, TEM, EDS, FTIR, UV–Vis) revealed that TiO 2 particles achieved better dispersion and interfacial binding capacity, effectively minimizing pore formation and structural defects. The dense oxide layer on TiO 2 surfaces amplified the “maze effect,” significantly inhibiting corrosive medium penetration. Cross-cut adhesion testing and impact resistance evaluation further confirmed the TiO 2 system's advantages in interfacial bonding strength and mechanical robustness over the TC4 counterpart. Collectively, the TiO 2 –mineral hybrid coating demonstrates superior comprehensive protection properties and greater engineering application potential, offering a novel strategy for designing cost-effective, high-performance waterborne epoxy anticorrosion materials.

Wire Arc Additive Manufacturing (WAAM) is a versatile and sustainable manufacturing technique for producing titanium components, with promising applications in sectors such as jewelry and interior design. WAAM technology offers advantages such as high deposition rates and efficient material usage. However, it often leads to the formation of thermal oxide layers and an alpha case on the surface, which can adversely affect mechanical properties and hinder coating adhesion. This study explores the effectiveness of environmentally sustainable chemical machining treatments based on oxalic acid and oxalic-ascorbic acid solutions for the surface preparation of WAAM-fabricated Ti6Al4V components before gold Physical Vapor Deposition (PVD). Samples were fabricated without inert atmosphere protection to minimize environmental impact. Treatments were performed at 60 °C, 75 °C, and 90 °C, and their effects on surface characteristics were evaluated through thickness loss measurements, roughness analysis, and elemental composition assessment. Conventional hydrofluoric-nitric acid treatments achieved complete oxide and alpha case removal within one hour. In contrast, organic treatments required 24 h at 90 °C to achieve similar results, with the addition of ascorbic acid accelerating the process. Organic treatments resulted in distinct surface morphologies, characterized by increased roughness, beneficial for coating adhesion. The deposited gold layer had a thickness of 198 ± 5 nm, as determined through X-ray fluorescence analysis. The results of the tape test indicated that coatings applied to samples treated with organic acids exhibited excellent adhesion, while those deposited on samples subjected to conventional treatments experienced delamination exceeding 65%.

This study used the RF magnetron sputtering technique to deposit titanium and aluminium-doped MoS2 coatings onto M50 steel substrates. The surface morphology and structural properties of the coatings were analysed using FESEM and XRD, respectively. Different vibrational modes present in the samples were analysed using Raman spectroscopy. Energy Dispersive Spectroscopy confirms the presence of Ti and Al in MoS2 coatings. The mechanical properties, including scratch hardness and critical load of failure, were investigated via a scratch tester with a Rockwell C diamond indenter. The Ti-Al-doped MoS2 coating exhibited the maximum scratch hardness of 15.49 GPa and the highest critical load of failure of 20 N. Tribological properties of the coatings were assessed on a multifunctional tribometer under loads ranging from 200 to 600 mN. The films exhibited friction coefficients ranging from 0.028 and 0.003. The wear properties are also assessed using a multifunctional tribometer under applied loads of 200 mN, 400 mN, and 600 mN. The wear rate increased with the applied load, ranging from a minimum of 13.5× 10-4 mm3/Nm at 200 mN to a maximum of 130 × 10-4 mm3/Nm for the Ti-Al-doped MoS2 film at 600 mN.

The demand for durable, oxidation-resistant coatings for high-temperature tooling requires an understanding of intermetallic phase formation and thermal stability. Intermetallic coatings are being explored more for use in high-temperature and chemically aggressive applications. The effect of thermal treatment on Fe/Al and Ni/Al coatings deposited by thermal spraying on grey cast iron substrates was investigated with emphasis on composition, microstructure and intermetallic phase formation. Annealing experiments at different temperatures provided insight into solid state diffusion processes. During annealing, interdiffusion between the coating and substrate components led to the formation of homogeneous intermetallic phases on the surface. The results showed that both chemical composition and annealing parameters influence the hardness of thermally sprayed coatings. Temperature and duration were found to have a significant effect on intermetallic phase formation. For Fe/Al coatings, annealing at 700°C resulted in the formation of FeAl and Fe 3 Al intermetallic compounds, whereas at 1000°C only the FeAl phase remained. In Ni/Al coatings, annealing at 700°C resulted in the formation of multiple phases, including Ni 3 Al, NiAl, and Ni 2 Al 3 , while at 1000°C only the NiAl phase was present. Optimization of thermal treatment processes can significantly improve the mechanical and chemical properties of coatings, making them suitable for a wide range of applications in industries.

The key processing issue with EDM of maraging steel is the formation of defective surfaces, including cracks, craters, voids, and globules, along with a recast layer. These defects degrade surface characteristics, leading to premature failure of EDM-fabricated critical components like aerospace landing gear and gyroscope flexures. To address this, the present study explores the effectiveness of organic-electrolyte-based electropolishing (EP) as a post-processing technique, replacing traditional sulfuric acid-based methods. The present research compares EDM and EP surfaces in terms of surface quality, morphology, phase composition, crystallite size, hardness, reflectance, wettability, and tribological performance. The EP process eliminates all the surface defects, enhancing surface quality. Peak broadening in EDM is attributed to micro-strain, which EP alleviates, aligning with the base material's strain levels. Hardness measurements show EDMed surfaces at 7.78 GPa, the base material at 4.11 GPa, and EP surfaces at 4.02 GPa. Reflectance increases from 12% to 78% post-EP, and wettability improves with a reduced contact angle. EP significantly enhances tribological performance by lowering friction, wear, and adhesion, making EDMed components more suitable for aviation applications like landing gear. These findings demonstrate significant improvement in surface characteristics after EP, offering a cost-effective, promising solution for EDMed maraging steel components.

Graphene is a promising nano-additive in polymer-based coatings to improve their tribology performance under current-carrying conditions due to its unique electrical, thermal and mechanical properties. Here, the current-carrying friction behavior of polyamide-imide (PAI) matrix composite coating incorporated with graphene prepared by high-temperature solicitation is studied using a homemade ball-on-disc tribometer. It is revealed that both coefficient of friction and wear rate of graphene/PAI composite coating are lower than those of pure PAI coating. The reduction in wear rate of PAI coating by the addition of graphene is increased by >7 times when the current intensity rises from 0 to 4.5 A, indicating better tribology enhancement of graphene under current-carrying conditions than under dry conditions. Post-test surface analyses demonstrate that the tribology enhancement mechanism mainly arises from the quick in-situ formation of graphene-rich transfer film promoted by current heat and the highly suppressed arc erosion on worn surface. This work provides a novel method to broaden wear resistant polymer-based coatings in the field of current-carrying lubrication application.