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Search Results (266)

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Keywords = MoO3-coated

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14 pages, 6773 KiB  
Article
MoTiCo Conversion Coating on 7075 Aluminium Alloy Surface: Preparation, Corrosion Resistance Analysis, and Application in Outdoor Sports Equipment Trekking Poles
by Yiqun Wang, Feng Huang and Xuzheng Qian
Metals 2025, 15(8), 864; https://doi.org/10.3390/met15080864 (registering DOI) - 1 Aug 2025
Viewed by 117
Abstract
The problem of protecting 7075 Al alloy trekking poles from corrosion in complex outdoor environments was addressed using a composite conversion coating system. This system comprised Na2MoO4, NaF, CoSO4·7H2O, ethylenediaminetetraacetic acid-2Na, and H2(TiF [...] Read more.
The problem of protecting 7075 Al alloy trekking poles from corrosion in complex outdoor environments was addressed using a composite conversion coating system. This system comprised Na2MoO4, NaF, CoSO4·7H2O, ethylenediaminetetraacetic acid-2Na, and H2(TiF6). The influences of this system on the properties of the coating layer were systematically studied by adjusting the pH of the coating solution. The conversion temperature and pH were the pivotal parameters influencing the formation of the conversion coating. The pH substantially influenced the compactness of the coating layer, acting as a regulatory agent of the coating kinetics. When the conversion temperature and pH were set to 40 °C and 3.8, respectively, the prepared coating layer displayed optimal performance in terms of compactness and protective properties. Therefore, this parameter combination favours the synthesis of high-performance conversion coatings. Microscopy confirmed the formation of a continuous, dense composite oxide film structure under these conditions, effectively blocking erosion in corrosive media. Furthermore, the optimised process led to substantial enhancements in the environmental adaptabilities and service lives of the components of trekking poles, thus establishing a theoretical foundation and technical reference for use in the surface protection of outdoor equipment. Full article
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23 pages, 3795 KiB  
Article
Structural Analysis of the Newly Prepared Ti55Al27Mo13 Alloy by Aluminothermic Reaction
by Štefan Michna, Jaroslava Svobodová, Anna Knaislová, Jan Novotný and Lenka Michnová
Materials 2025, 18(15), 3583; https://doi.org/10.3390/ma18153583 - 30 Jul 2025
Viewed by 153
Abstract
This study presents the structural and compositional characterisation of a newly developed Ti55Al27Mo13 alloy synthesised via aluminothermic reaction. The alloy was designed to overcome the limitations of conventional processing routes for high–melting–point elements such as Ti and Mo, enabling the formation of a [...] Read more.
This study presents the structural and compositional characterisation of a newly developed Ti55Al27Mo13 alloy synthesised via aluminothermic reaction. The alloy was designed to overcome the limitations of conventional processing routes for high–melting–point elements such as Ti and Mo, enabling the formation of a complex, multi–phase microstructure in a single high–temperature step. The aim was to develop and characterise a material with microstructural features expected to enhance wear resistance, oxidation behaviour, and thermal stability in future applications. The alloy is intended as a precursor for composite nanopowders and surface coatings applied to aluminium–, magnesium–, and iron–based substrates subjected to mechanical and thermal loading. Elemental analysis (XRF, EDS) confirmed the presence of Ti, Al, Mo, and minor elements such as Si, Fe, and C. Microstructural investigations using laser confocal and scanning electron microscopy revealed a heterogeneous structure comprising solid solutions, eutectic regions, and dispersed oxide and carbide phases. Notably, the alloy exhibits high hardness values, reaching >2400 HV in Al2O3 regions and ~1300 HV in Mo– and Si–enriched solid solutions. These results suggest the material’s substantial potential for protective surface engineering. Further tribological, thermal, and corrosion testing, conducted with meticulous attention to detail, will follow to validate its functional performance in target applications. Full article
(This article belongs to the Section Metals and Alloys)
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14 pages, 4332 KiB  
Article
Powerful Tribocatalytic Degradation of Methyl Orange Solutions with Concentrations as High as 100 mg/L by BaTiO3 Nanoparticles
by Mingzhang Zhu, Zeren Zhou, Yanhong Gu, Lina Bing, Yuqin Xie, Zhenjiang Shen and Wanping Chen
Nanomaterials 2025, 15(14), 1135; https://doi.org/10.3390/nano15141135 - 21 Jul 2025
Viewed by 291
Abstract
In sharp contrast to photocatalysis and other prevalent catalytic technologies, tribocatalysis has emerged as a promising technology to degrade high-concentration organic dyes in recent years. In this study, BaTiO3 (BTO) nanoparticles were challenged to degrade methyl orange (MO) solutions with unprecedentedly high [...] Read more.
In sharp contrast to photocatalysis and other prevalent catalytic technologies, tribocatalysis has emerged as a promising technology to degrade high-concentration organic dyes in recent years. In this study, BaTiO3 (BTO) nanoparticles were challenged to degrade methyl orange (MO) solutions with unprecedentedly high concentrations through magnetic stirring. With BTO nanoparticles and home-made PTFE magnetic rotary disks in 50 mg/L MO solutions, 10 h of magnetic stirring resulted in 91.4% and 98.1% degradations in an as-received glass beaker and in a beaker with a PTFE disk coated on its bottom, respectively. Even for 100 mg/L MO solutions, nearly complete degradation was achieved by magnetic-stirring-stimulated BTO nanoparticles in beakers with the following four kinds of bottom: 97.3% degradation in 30 h for a glass bottom, 97.4% degradation in 20 h for a PTFE coating, 97.9% degradation in 42 h for a Ti coating, and 97.4% degradation in 74 h for an Al2O3 coating. Electron paramagnetic resonance (EPR) analyses revealed that the generation of reactive oxygen species (ROS) by magnetic-stirring-stimulated BTO nanoparticles is dramatically affected by the bottom material of beakers. These findings suggest an appealing prospect for BTO nanoparticles to utilize mechanical energy for sustainable water remediation. Full article
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13 pages, 2184 KiB  
Article
A Comparative Study on the High-Temperature Oxidation Behavior and Mechanisms of Micro/Nanoparticle Composite-Modified Chromium Carbide Metal Ceramic Coatings
by Linwen Wang, Jiawei Wang, Haiyang Lu, Jiyu Du, Xiaoxia Qi, Laixiao Lu and Ziwu Liu
Coatings 2025, 15(7), 826; https://doi.org/10.3390/coatings15070826 - 15 Jul 2025
Viewed by 218
Abstract
To enhance the high-temperature oxidation resistance of chromium carbide metal ceramic coatings, micro/nanoparticle modification was applied to the alloy binder phase of the typical Cr3C2-NiCr coating. This led to the development of Cr3C2-NiCrCoMo and Cr [...] Read more.
To enhance the high-temperature oxidation resistance of chromium carbide metal ceramic coatings, micro/nanoparticle modification was applied to the alloy binder phase of the typical Cr3C2-NiCr coating. This led to the development of Cr3C2-NiCrCoMo and Cr3C2-NiCrCoMo/nano-CeO2 coatings with superior high-temperature oxidation performance. This study compares the high-temperature oxidation behavior of these coating samples and explores their respective oxidation mechanisms. The results indicate that the addition of CoCrMo improves the compatibility between the oxide film and the coating, enhancing the microstructure and integrity of the oxide film. Compared to Cr3C2-NiCrCoMo coatings, the incorporation of nano-CeO2 promotes the reaction between oxides in the Cr3C2-NiCrCoMo/nano-CeO2 coating, increasing the content of binary spinel phases, reducing thermal stress at the oxide–coating interface, and improving the adhesion strength of the oxide film. As a result, the oxidation rate of the coating is reduced, and its oxidation resistance is improved. Full article
(This article belongs to the Special Issue Ceramic-Based Coatings for High-Performance Applications)
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14 pages, 4114 KiB  
Article
Effect of Silica Sol on the Preparation and Oxidation Resistance of MoSi2@SiO2
by Linlin Guo, Jinjun Zhang, Chengpeng Miao, Shuang Feng, Xiaozhen Fan, Haiyan Du, Jiachen Liu and Mingchao Wang
Materials 2025, 18(13), 3203; https://doi.org/10.3390/ma18133203 - 7 Jul 2025
Viewed by 246
Abstract
The limited oxidation resistance of MoSi2 between 400 °C and 600 °C restricts its aerospace applications. This study develops a silica-sol derived core-shell MoSi2@SiO2 composite to enhance the low-temperature oxidation resistance of MoSi2. Acidic, neutral, and basic [...] Read more.
The limited oxidation resistance of MoSi2 between 400 °C and 600 °C restricts its aerospace applications. This study develops a silica-sol derived core-shell MoSi2@SiO2 composite to enhance the low-temperature oxidation resistance of MoSi2. Acidic, neutral, and basic silica sols were systematically applied to coat MoSi2 powders through sol-adsorption encapsulation. Two pathways were used, one was ethanol-mediated dispersion, and the other was direct dispersion of MoSi2 particles in silica sol. Analysis demonstrated that ethanol-mediated dispersion significantly influenced the coating efficiency and oxidation resistance, exhibited significantly decreased coating weight gains (maximum 27%) and increased oxidation weight gains (10–20%) between 340 °C and 600 °C compared with direct dispersion of MoSi2 particles with silica sol, ascribe to the kinetic inhibition of hydroxyl group condensation and steric hindrance of MoSi2-silica sol interface interactions of ethanol. Systematic investigation of silica sol encapsulation of MoSi2 revealed critical correlations between colloid properties and oxidation resistance of MoSi2@SiO2. Basic silica sol coated MoSi2 (BS-MoSi2) exhibits the lowest coating efficiency (coating weight gain of 7.74 ± 0.06%) as well as lowest oxidation weight gain (18.45%) between 340 °C and 600 °C compared with those of acid and neutral silica sol coated MoSi2 (AS-MoSi2 and NS-MoSi2), arises from optimal gelation kinetics, enhanced surface coverage via reduced agglomeration, and suppressed premature nucleation through controlled charge interactions under alkaline conditions. Full article
(This article belongs to the Section Advanced and Functional Ceramics and Glasses)
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14 pages, 7044 KiB  
Article
Microstructure, Wear and Corrosion Properties of Inconel 718-CeO2 Composite Coatings
by Yu Liu, Guohui Li, Hui Liang, Zhanhui Zhang, Zeyu Li and Haiquan Jin
Coatings 2025, 15(7), 783; https://doi.org/10.3390/coatings15070783 - 2 Jul 2025
Viewed by 296
Abstract
Based on laser cladding technology, six composite coatings with different amounts of Inconel 718 and 0~5% CeO2 were successfully prepared on the 316L stainless steel substrate. The effect of different amounts of CeO2 particles was investigated and discussed, such as microstructure, [...] Read more.
Based on laser cladding technology, six composite coatings with different amounts of Inconel 718 and 0~5% CeO2 were successfully prepared on the 316L stainless steel substrate. The effect of different amounts of CeO2 particles was investigated and discussed, such as microstructure, phases, elemental distribution, microhardness, wear resistance and corrosion resistance. The results show that the phases are composed of γ~(Fe, Ni), Ni3Nb, (Nb0.03Ti0.97)Ni3, and MCX(M = Cr, Nb and Mo). When the amount of CeO2 particles is higher than 1%, some Ce2O3 compounds can be detected in coatings. The average microhardness values of N0~N5 are 604.6, 754.5, 771.6, 741.4, 694.5 and 677.3 HV0.2, respectively. There is a trend that the microhardness increases firstly and then decreases, because an appropriate amount of CeO2 can improve the solid solution strength. The average wear rate values of N0~N5 are 2.97 × 10−5, 1.22 × 10−5, 0.94 × 10−5, 1.53 × 10−5, 1.81 × 10−5 and 2.26 × 10−5 mm3∙N−1∙min−1, respectively. The N2 coating has the smallest corrosion current density of 2.05 × 10−4 A·cm−2, which is about 56% of the N0 coating. When the amount of CeO2 particles is 2%, the coating has the best wear resistance and corrosion resistance due to fine grains and Cr, Nb and Mo compounds. Full article
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14 pages, 3484 KiB  
Article
Al2O3@SiO2 Supported NiMo Catalyst with Hierarchical Meso-Macroporous Structure for Hydrodemetallization
by Weichu Li, Jun Bao, Shuangqin Zeng, Jinbao Zheng, Weiping Fang, Xiaodong Yi, Qinghe Yang and Weikun Lai
Catalysts 2025, 15(7), 646; https://doi.org/10.3390/catal15070646 - 1 Jul 2025
Viewed by 384
Abstract
The pore structure of a hydrotreating catalyst plays a pivotal role in hydrodemetallization (HDM) reactions. To effectively construct a meso-macroporous catalyst, we employed a CTAB-guided in situ TEOS hydrolysis approach to prepare silica-coated γ-Al2O3@SiO2 composite supports. The silica [...] Read more.
The pore structure of a hydrotreating catalyst plays a pivotal role in hydrodemetallization (HDM) reactions. To effectively construct a meso-macroporous catalyst, we employed a CTAB-guided in situ TEOS hydrolysis approach to prepare silica-coated γ-Al2O3@SiO2 composite supports. The silica shell incorporation significantly enhances specific surface area and reduces the metal–support interactions, thereby improving the dispersion of NiMo active components and boosting the deposition of metal impurity. Hence, the NiMo/Al2O3@SiO2 catalyst (2.8 wt.% NiO, 4.3 wt.% MoO3) exhibits much higher HDM activity than that of NiMo/Al2O3. This is evidenced by markedly higher demetallization rate constant (1.38 h−1) and turnover frequency (0.56 h−1) of the NiMo/Al2O3@SiO2. The NiMo/Al2O3@SiO2 catalyst further demonstrates excellent recyclability during sequential HDM reactions. This superior catalytic behavior stems from the hierarchical meso-macroporous structure, which simultaneously facilitates the deposition of metal impurities and mitigates deactivation by pore blockage. Full article
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20 pages, 23355 KiB  
Article
Unveiling Thickness-Dependent Oxidation Effect on Optical Response of Room Temperature RF-Sputtered Nickel Ultrathin Films on Amorphous Glass: An Experimental and FDTD Investigation
by Dylan A. Huerta-Arteaga, Mitchel A. Ruiz-Robles, Srivathsava Surabhi, S. Shiva Samhitha, Santhosh Girish, María J. Martínez-Carreón, Francisco Solís-Pomar, A. Martínez-Huerta, Jong-Ryul Jeong and Eduardo Pérez-Tijerina
Materials 2025, 18(12), 2891; https://doi.org/10.3390/ma18122891 - 18 Jun 2025
Viewed by 478
Abstract
Nickel (Ni) ultrathin films exhibit phase-dependent electrical, magnetic, and optical characteristics that are significantly influenced by deposition methods. However, these films are inherently prone to rapid oxidation, with the oxidation rate dependent on substrate, temperature, and deposition parameters. The focus of this research [...] Read more.
Nickel (Ni) ultrathin films exhibit phase-dependent electrical, magnetic, and optical characteristics that are significantly influenced by deposition methods. However, these films are inherently prone to rapid oxidation, with the oxidation rate dependent on substrate, temperature, and deposition parameters. The focus of this research is to investigate the temporal oxidation of RF-sputtered Ni ultrathin films on Corning glass under ambient atmospheric conditions and its impact on their structural, surface, and optical characteristics. Controlled film thicknesses were achieved through precise manipulation of deposition parameters, enabling the analysis of oxidation-induced modifications. Atomic force microscopy (AFM) revealed that films with high structural integrity and surface uniformity are exhibiting roughness values (Rq) from 0.679 to 4.379 nm of corresponding thicknesses ranging from 4 to 85 nm. Scanning electron microscopy (SEM) validated the formation of Ni grains interspersed with NiO phases, facilitating SPR-like effects. UV-visible spectroscopy is demonstrating thickness-dependent spectral (plasmonic peak) shifts. Finite Difference Time Domain (FDTD) simulations corroborate the observed thickness-dependent optical absorbance and the resultant shifts in the absorbance-induced plasmonic peak position and bandgap. Increased NiO presence primarily drives the enhancement of electromagnetic (EM) field localization and the direct impact on power absorption efficiency, which are modulated by the tunability of the plasmonic peak position. Our work demonstrates that controlled fabrication conditions and optimal film thickness selection allow for accurate manipulation of the Ni oxidation process, significantly altering their optical properties. This enables the tailoring of these Ni films for applications in transparent conductive electrodes (TCEs), magneto-optic (MO) devices, spintronics, wear-resistant coatings, microelectronics, and photonics. Full article
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20 pages, 6335 KiB  
Article
Electroplating Composite Coatings of Nickel with Dispersed WO3 and MoO3 on Al Substrate to Increase Wear Resistance
by Petr Osipov, Roza Shayakhmetova, Danatbek Murzalinov, Azamat Sagyndykov, Ainur Kali, Anar Mukhametzhanova, Galymzhan Maldybayev and Konstantin Mit
Materials 2025, 18(12), 2781; https://doi.org/10.3390/ma18122781 - 13 Jun 2025
Viewed by 490
Abstract
Investigations of the synthesis of multicomponent coatings and their subsequent application to metal substrates to increase the wear resistance of materials is relevant for industry. Nickel compounds obtained from oxidized magnesia-iron nickel ores with a desorption rate of more than 94% were used [...] Read more.
Investigations of the synthesis of multicomponent coatings and their subsequent application to metal substrates to increase the wear resistance of materials is relevant for industry. Nickel compounds obtained from oxidized magnesia-iron nickel ores with a desorption rate of more than 94% were used to create Ni-MoO3-WO3 electroplating. Such composite samples formed from an aqueous alcohol solution reduced the content of sodium and ammonium chlorides. The annealing and dehydration of samples at a temperature of 725 °C in an air atmosphere made it possible to achieve the highest level of crystallinity. In this case, an isomorphic substitution of W atoms by Mo occurs, which is confirmed by electron paramagnetic resonance (EPR) spectroscopy studies. The invariance of the shape of the EPR spectrum with a sequential increase in microwave radiation power revealed the stability of the bonds between the particles. The surface morphology of Ni-MoO3-WO3 films deposited on an Al substrate is smooth and has low roughness. In this case, an increased degree of wear resistance has been achieved. Thus, a recipe for the formation of an electroplating with stable bonds between the components and increased wear resistance was obtained. Full article
(This article belongs to the Section Advanced Composites)
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18 pages, 8036 KiB  
Article
Research on High-Temperature Frictional Performance Optimization and Synergistic Effects of Phosphate-Based Composite Lubricating Coatings
by Yong Ding, Shengjun Wang, Youxin Zhou, Hongmei Lv and Baoping Yang
Coatings 2025, 15(6), 704; https://doi.org/10.3390/coatings15060704 - 11 Jun 2025
Viewed by 490
Abstract
In high-temperature, high-pressure, and corrosive industrial environments, frictional wear of metallic components stands as a critical determinant governing the long-term operational reliability of mechanical systems. To address the challenge of traditional lubricating coating failure under a broad temperature range (−50 to 500 °C), [...] Read more.
In high-temperature, high-pressure, and corrosive industrial environments, frictional wear of metallic components stands as a critical determinant governing the long-term operational reliability of mechanical systems. To address the challenge of traditional lubricating coating failure under a broad temperature range (−50 to 500 °C), this study developed a phosphate-based composite lubricating coating. Through air-spraying technology and orthogonal experimental optimization, the optimal formulation was determined as follows: binder/filler ratio = 6:4, 5% graphite, 15% MoS2, and 10% aluminum powder. Experimental results demonstrated that at 500 °C, the coating forms an Al–O–P cross-linked network structure, with MoS2 oxidation generating MoO3 and aluminum powder transforming into Al2O3, significantly enhancing density and oxidation resistance. Friction tests revealed that the composite coating achieves a friction coefficient as low as 0.12 at room temperature with a friction time of 260 min. At 500 °C, the friction coefficient stabilizes at 0.24, providing 40 min of effective protection. This technology not only resolves the high-temperature instability of traditional coatings but also ensures an environmentally friendly preparation process with no harmful emissions, offering a technical solution for the protection of high-temperature equipment such as thermal power plant boiler tubes and petrochemical reactors. Full article
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12 pages, 1878 KiB  
Article
Photocatalytic Properties of ZnO/WO3 Coatings Formed by Plasma Electrolytic Oxidation of a Zinc Substrate in a Tungsten-Containing Electrolyte
by Stevan Stojadinović, Dejan Pjević and Nenad Radić
Coatings 2025, 15(6), 657; https://doi.org/10.3390/coatings15060657 - 29 May 2025
Viewed by 487
Abstract
ZnO/WO3 coatings were synthesized by the plasma electrolytic oxidation of zinc in an alkaline phosphate electrolyte (supporting electrolyte, SE) with the addition of WO3 particles or tungstosilicic acid (WSiA, H4SiW12O40) at concentrations of up to [...] Read more.
ZnO/WO3 coatings were synthesized by the plasma electrolytic oxidation of zinc in an alkaline phosphate electrolyte (supporting electrolyte, SE) with the addition of WO3 particles or tungstosilicic acid (WSiA, H4SiW12O40) at concentrations of up to 1.0 g/L. These coatings were intended for the decomposition of methyl orange (MO) through photocatalysis. The morphology, chemical composition, crystal structure and absorption properties of the coatings were investigated using scanning electron microscopy, energy dispersive X-ray spectroscopy, wavelength-dispersive X-ray spectroscopy, X-ray diffraction, photoelectron spectroscopy and diffuse reflectance spectroscopy. Under artificial sunlight, the PA of the coatings was investigated using MO decomposition. The photocatalytic activity (PA) of the ZnO/WO3 coatings was higher than that of the ZnO obtained in SE. The decrease in the recombination rate of photo-generated electron/hole pairs due to the coupling of ZnO and WO3 is related to the increased PA. The PA for ZnO and the most photocatalytically active ZnO/WO3 was around 72% and 96%, respectively, after 8 h of irradiation. A mechanism for MO photo-degradation by the ZnO/WO3 photocatalyst was also proposed. Full article
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17 pages, 2429 KiB  
Article
Experimental Investigation on Cutting Forces in Sustainable Hard Milling of Hardox 500 Steel Under Al2O3/MoS2 Hybrid Nanofluid MQCL Environment
by Tran The Long
Lubricants 2025, 13(6), 240; https://doi.org/10.3390/lubricants13060240 - 26 May 2025
Cited by 1 | Viewed by 512
Abstract
Hardox 500 is a special low-alloy, martensitic steel possessing extraordinary wear resistance, high hardness, and high ductility; thus, it has been widely used in many industrial applications. Nevertheless, this type of steel has a low machinability and is grouped among the difficult-to-machine materials. [...] Read more.
Hardox 500 is a special low-alloy, martensitic steel possessing extraordinary wear resistance, high hardness, and high ductility; thus, it has been widely used in many industrial applications. Nevertheless, this type of steel has a low machinability and is grouped among the difficult-to-machine materials. Hence, this paper’s objective was to study its hard milling performance under minimum quantity cooling lubrication (MQCL) conditions using an Al2O3/MoS2 hybrid nano cutting oil. The Box–Behnken response surface methodology was used to investigate the effects of the nanoparticle concentration (NC), cutting speed (v), and feed rate (f) on the total cutting force F and cutting force coefficient Fy/Fz. The obtained results indicate that the cutting efficiency of Hardox 500 steel was improved thanks to the enhancement in cooling lubrication from the MQCL using the Al2O3/MoS2 hybrid nano cutting oil. The applicability of vegetable oil and coated carbide inserts is thus extended to the hard milling of difficult-to-cut materials. Moreover, the provision of the appropriate ranges and optimal set of investigated variables obtained in this paper will be useful guides for technologists and further studies. Concretely, NC = 0.5–0.7%, v = 110–115 m/min, and f = 0.08–0.10 mm/tooth are the optimal set for the total cutting force F, while NC = 0.5%, v = 138–140 m/min, and f = 0.08–0.09 mm/tooth are suggested for the cutting force coefficient Fy/Fz. Full article
(This article belongs to the Special Issue Recent Advances in Tribological Properties of Machine Tools)
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27 pages, 21703 KiB  
Article
Optimization of Ni-B-Mo Electroless Coating on GCr15 Steel: Effects of Main Salt Concentration and Deposition Time
by Shunqi Mei, Xiaohui Zou, Zekui Hu, Jinyu Yang, Quan Zheng, Wei Huang, Alexey Guryev and Burial Lygdenov
Materials 2025, 18(9), 1981; https://doi.org/10.3390/ma18091981 - 27 Apr 2025
Cited by 1 | Viewed by 524
Abstract
GCr15 bearing steel is widely used in the textile, aerospace, and other industries due to its excellent mechanical properties. However, traditional electroless Ni-B coatings can no longer meet the growing demand for a long service life under high-speed and heavy load conditions. This [...] Read more.
GCr15 bearing steel is widely used in the textile, aerospace, and other industries due to its excellent mechanical properties. However, traditional electroless Ni-B coatings can no longer meet the growing demand for a long service life under high-speed and heavy load conditions. This study focused on depositing Ni-B-Mo alloy coatings on GCr15 steel. An orthogonal experimental design was adopted to investigate the effects of the NiCl2 and Na2MoO4 concentrations and deposition time on the deposition rate and surface hardness of the coatings. The results show that the Na2MoO4 concentration has the most significant impact on the deposition rate. An optimal concentration of 5.6 g/L improved both the deposition rate and hardness (up to 881 HV), while excessive Na2MoO4 (>15.6 g/L) reduced the coating adhesion and wear resistance. A deposition time of 1–2 h ensured a high deposition rate, but after 3 h, bath component depletion lowered the rate and caused coating defects. The NiCl2 concentration (20–30 g/L) had a relatively minor influence on the deposition rate but stabilized the Ni2+ ion supply, enhancing the coating compactness. The optimized parameters were 5.6 g/L Na2MoO4, 25 g/L NiCl2, and 2 h of deposition. The coating exhibited high hardness, strong adhesion, and excellent wear resistance. After heat treatment at 400 °C for 1 h, the coating transitioned from being amorphous to nanocrystalline, forming Ni2B, Ni3B, and Mo2C phases, increasing the hardness from 737.49 HV to 916.19 HV and reducing the friction coefficient to 0.38. Full article
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12 pages, 14079 KiB  
Article
Preparation of High-Entropy Silicide Coating on Tantalum Substrate by Silicon Infiltration Method and Its Antioxidant Performance
by Xinli Liu, Dexiang Tian, Jiali Mao, Gang Zhao and Dezhi Wang
Coatings 2025, 15(4), 476; https://doi.org/10.3390/coatings15040476 - 17 Apr 2025
Viewed by 413
Abstract
High-entropy silicide (MeSi2) coating was prepared by the slurry method and silicon infiltration method using Mo, Cr, Ta, Nb, W, and Si elemental powders as raw materials. The coating consisted of four layers, including a porous MeSi2 layer, a (CrTa)Si [...] Read more.
High-entropy silicide (MeSi2) coating was prepared by the slurry method and silicon infiltration method using Mo, Cr, Ta, Nb, W, and Si elemental powders as raw materials. The coating consisted of four layers, including a porous MeSi2 layer, a (CrTa)Si layer, a TaSi2 layer, and a Ta5Si3 layer from outside to inside. At 600 °C, Si was preferentially oxidized to form SiO2 oxide film. The mass gain rate of the coating was 0.2 mg/cm2 over a period of 100 h oxidation, eliminating the phenomenon of low-temperature pulverization. At 1200 °C, MeSi2 coating had a protection time of 20 h. During the oxidation process, the coating generated metal oxides, forming a thin SiO2 oxide film. TaSi2 and Ta5Si3 gradually transformed into Ta2O5, and the coating eventually failed. Full article
(This article belongs to the Section Ceramic Coatings and Engineering Technology)
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17 pages, 4124 KiB  
Article
Effect of NaAlO2 Co-Electrical Parameters on the Wear Resistance of MAO/MoS2 Self-Lubricating Composite Coatings
by Feiyan Liang, Erhui Yang, Na Jia, Weizhou Li, Xiaolian Zhao and Ruixia Yang
Materials 2025, 18(8), 1825; https://doi.org/10.3390/ma18081825 - 16 Apr 2025
Viewed by 566
Abstract
This study aims to enhance the wear resistance of MAO/MoS2 composite coatings fabricated on TC4 titanium alloy substrates through a composite process of microarc oxidation (MAO) and hydrothermal synthesis. The MAO treatment experiments were designed according to the L16 (45) [...] Read more.
This study aims to enhance the wear resistance of MAO/MoS2 composite coatings fabricated on TC4 titanium alloy substrates through a composite process of microarc oxidation (MAO) and hydrothermal synthesis. The MAO treatment experiments were designed according to the L16 (45) orthogonal array to optimize the NaAlO2 concentration and electrical parameters (oxidation voltage, frequency, duty ratio, and treating time), with four levels for each factor. The optimized MAO process parameters were identified as a NaAlO2 concentration of 10 g/L, an oxidation voltage of 500 V, a frequency of 200 Hz, a duty ratio of 20%, and a treating time of 30 min. The experimental results indicated a notable reduction in porosity, from 4.45% to 0.30%, in the optimized composite coating. Concurrently, there was a 43.2% increase in microhardness and a 327.9% increase in adhesive strength. Furthermore, the average coefficient of friction (CoF) of the composite coating was observed to be 0.13 at a high load of 20 N and a wear time of 20 min, representing a significant reduction of 68.5% compared to the CoF of the single MAO coating. Full article
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