Search Results (1,549)

In this paper, silver oxide (AgO) and copper oxide (CuO) coatings are placed on a single sputtering target with the direct-current magnetron sputtering (DCMS) and high-power impulse magnetron sputtering (HIPIMS) methods. All the tested coatings are obtained in a reactive process using a metallic target made by the Kurt Lesker company. The investigated coatings are deposited at room temperature on substrates made of pure iron (ARMCO) and polypropylene (PP) without substrate polarization. The deposition time for all the coatings is the same. The results of SEM and TEM investigations clearly show that using the HIPIMS method for the deposition of AgO and CuO coatings reduces their thickness and increases their structure density. Coatings produced with the HIPIMS method are characterized by a higher hardness and Young’s modulus. The value of hardness for AgO and CuO coatings deposited by the HIPIMS method is around 50% higher for AgO coatings and around 24% higher for CuO coatings compared to the coatings obtained by the DC method. This is also true of Young’s modulus values, which are around 30% higher for AgO coatings and 15% higher for CuO coatings produced by the HIPIMS method compared to those of coatings obtained with the DC method. AgO and CuO coatings deposited with both the methods (HIPIMS and DCMS) showed 100% reduction in the viability of two reference laboratory bacteria strains—Escherichia coli (Gram−) and Staphylococcus aureus (Gram+)—on both types of substrates. Additionally, these coatings are characterized by their hydrophobic properties, which means that they can create a protective barrier, making it difficult for bacteria to stick to the surface, limiting their development and preventing the phenomenon of biofouling. The HIPIMS technology allows for the deposition of coatings with better mechanical properties than those produced with the DCMS method, which means that they are more resistant to brittle fractures and wear and have very good antimicrobial properties. Full article

Water walls in power plant boilers are prone to failure under extreme conditions involving high temperature, corrosion, and wear, which severely threaten unit reliability and operational economy. In this work, a NiCr-Cr₃C₂ protective coating was deposited on SA213-T12 steel substrates using high-velocity oxy-fuel (HVOF) spraying, with arc-sprayed PS45 coating as a reference. The NiCr-Cr₃C₂ coating exhibited a dense, low-porosity structure with homogeneous dispersion of Cr₃C₂ hard phases in the NiCr matrix, forming a typical cauliflower-like composite morphology. During high-temperature sulfate corrosion tests at 750 °C, the NiCr-Cr₃C₂ coating demonstrated superior corrosion resistance, with a weight gain of only 2.7 mg/cm², significantly lower than that of the PS45 coating and the SA213-T12 substrate. The higher microhardness and lower friction coefficient also indicate excellent high-temperature wear resistance. The enhanced performance of the NiCr-Cr₃C₂ coating is attributed to the high Cr content, which promotes the formation of a continuous and protective scale composed of Cr₂O₃ and NiCr₂O₄, effectively inhibiting corrosive diffusion and penetration. This work demonstrates the application prospects of NiCr-Cr₃C₂ coatings on water walls of power plant boilers and guides the development of advanced HVOF coatings. Full article

Diamond-like carbon (DLC) films are valued for their high hardness and wear resistance, but their application in harsh environments is limited by high internal stress and poor corrosion resistance. Co-doping with transition metals offers a promising route to overcome these drawbacks by tailoring microstructure and enhancing multifunctional performance. However, the synergistic effects of Ni and Cr co-doping in DLC remain underexplored. In this study, Ni and Cr co-doped DLC (NiCr-DLC) films were fabricated using filtered cathodic vacuum arc deposition (FCVAD). By varying the C₂H₂ flow rate, the carbon content and microstructure evolved from columnar to fine-grained and compact structures. The optimized film (F55) achieved an ultralow surface roughness (Sa = 0.26 nm), even smoother than the Si substrate. The Ni–Cr co-doping promoted a nanocomposite structure, yielding a maximum hardness of 15.56 GPa and excellent wear resistance (wear rate: 4.45 × 10⁻⁷ mm³/N·m). Electrochemical tests revealed significantly improved corrosion resistance compared to AISI 304L stainless steel, with F55 exhibiting the highest corrosion potential, the lowest current density, and the largest impedance modulus. This work demonstrates that Ni-Cr co-doping effectively enhances the mechanical and corrosion properties of DLC films while improving surface quality, providing a viable strategy for developing robust, multifunctional protective coatings for demanding applications in aerospace, automotive, and biomedical systems. Full article

This study systematically investigates the effects of welding current on the macro-morphology, microstructure, mechanical properties, and corrosion resistance of Cu-Mn-Al alloy coatings deposited on 27SiMn steel substrates using Cold Metal Transfer (CMT) technology. The 27SiMn steel is widely applied in coal mining, geology, and engineering equipment due to its high strength and toughness, but its poor corrosion and wear resistance significantly limits service life. To address this issue, a Cu-Mn-Al alloy (high-manganese aluminum bronze) was selected as a cladding material because of its superior combination of mechanical strength, toughness, and excellent corrosion resistance in saline and marine environments. Compared with conventional cladding processes, CMT technology enables low-heat-input deposition, reduces dilution from the substrate, and promotes defect-free coating formation. To the best of our knowledge, this is the first report on the fabrication of Cu-Mn-Al coatings on 27SiMn steel using CMT, aiming to optimize process parameters and establish the relationship between welding current, phase evolution, and coating performance. The experimental results demonstrate that the cladding layer width increases progressively with welding current, whereas the layer height remains relatively stable at approximately 3 mm. At welding currents of 120 A and 150 A, the cladding layer primarily consists of α-Cu, κII, β-Cu₃Al, and α-Cu + κIII phases. At higher welding currents (180 A and 210 A), the α-Cu + κIII phase disappears, accompanied by the formation of petal-shaped κI phase. The peak shear strength (509.49 MPa) is achieved at 120 A, while the maximum average hardness (253 HV) is obtained at 150 A. The 120 A cladding layer demonstrates optimal corrosion resistance. These findings provide new insights into the application of CMT in fabricating Cu-Mn-Al protective coatings on steel and offer theoretical guidance for extending the service life of 27SiMn steel components in aggressive environments. Full article

Beta (β)-type Ti-29Nb-13Ta-4.6Zr (TNTZ) alloys combine low modulus with biocompatibility but require improved surface properties for long-term implantation. This study aimed to enhance the surface mechanical strength and antibacterial performance of TNTZ by applying TiN and TiAlN coatings via PVD. Notably, TiAlN was deposited on TNTZ for the first time, enabling a direct side-by-side comparison with TiN under identical deposition conditions. Dense TiN (~1.06 μm) and TiAlN (~1.73 μm) coatings were deposited onto solution-treated TNTZ and characterized by X-ray diffraction, scanning probe microscopy, Vickers microhardness, Rockwell indentation test (VDI 3198), static water contact angle measurements, and a Kirby–Bauer disk-diffusion antibacterial assay against Escherichia coli (E. coli). Both coatings formed face-centered cubic (FCC) structures with smooth interfaces (Ra ≤ 5.3 nm) while preserving the single-phase β matrix of the substrate. The hardness increased from 192 HV (uncoated) to 1059 HV (TiN) and 1468 HV (TiAlN), and the adhesion quality was rated as HF2 and HF1, respectively. The surface wettability changed from hydrophilic (48°) to moderately hydrophobic (82°) with TiN and highly hydrophobic (103°) with TiAlN. Similarly, the diameter of the no-growth zones increased to 18.02 mm (TiN) and 19.09 mm (TiAlN) compared to 17.65 mm for uncoated TNTZ. The findings indicate that TiAlN, in particular, provided improved hardness, adhesion, and hydrophobicity. Preliminary bacteriostatic screening under diffusion conditions suggested a modest relative antibacterial response, though the effect was not statistically significant between coated and uncoated TNTZ. Statistical analysis confirmed no significant difference between the groups (p > 0.05), indicating that only a preliminary bacteriostatic trend— rather than a definitive antibacterial effect—was observed. Both nitride coatings strengthened TNTZ without compromising its structural integrity, making TiAlN-coated TNTZ a promising candidate for next-generation orthopedic implants. Full article

A duplex coating system, consisting of a laser-cladded Fe-Cr-based interlayer and a silicon-doped diamond-like carbon (Si-DLC) top layer, was deposited on medium carbon steel substrate using laser cladding (LC) followed by plasma-enhanced chemical vapor deposition (PECVD). The LC interlayer (thickness of 1.5 mm, hardness of 455–620 HV0.3) was applied on both argon ion-etched and non-etched substrate surfaces. The microstructure and adhesion strength of the coatings were systematically investigated. The results show that the LC interlayer significantly enhanced the mechanical support for the Si-DLC coating, increasing adhesion strength by 4~5 times compared to direct deposition. Argon ion etching introduced micro-roughened surface features, increasing interfacial contact area and further boosting adhesion. A synergistic effect was observed between substrate hardness and ion etching in enhancing Si-DLC coating adhesion. Full article

The polymer deposition layer (PDL) formed during inductively coupled plasma (ICP) processing significantly limits the figuring accuracy and surface quality of fused silica optics. This study investigates the formation mechanism, composition, and evolution of the PDL under varying dwell times and proposes an innovative dwell time gradient strategy to suppress roughness deterioration. A significant disparity in hardness and elastic modulus between the deposition layer and the substrate is revealed, explaining its preferential removal and protective buffering effect in computer-controlled optical surfacing (CCOS). A hybrid ICP-CCOS polishing process was developed for processing a ϕ100 mm fused silica mirror. The results show that within 33 min, the surface graphic error RMS was significantly reduced from 58.006 nm to 12.111 nm, and within 90 min, the surface roughness was ultra-precisely reduced from Ra 1.719 nm to Ra 0.151 nm. The average processing efficiency was approximately 0.63 cm²/min. Critically, a damage-free, ultra-smooth surface without subsurface damage (SSD) was successfully achieved. This hybrid process enables the simultaneous optimization of figure accuracy and roughness, eliminating the need for iterative figuring cycles. It provides a novel theoretical framework for high-precision figuring and post-ICP polymer removal, advancing the efficient fabrication of high-performance optics. Full article

Gallium-based liquid metal is corrosive to steel alloys, forming FeGa₃ surface films which can potentially be applied as a solid lubricant to enhance wear resistance and mitigate liquid metal-induced corrosion. However, the characteristics of these films remain insufficiently explored. In this study, Ga-In-Sn alloy was ultrasonically soldered onto annealed and decarburised substrates, followed by heating in a vacuum chamber to form a 30 μm thick FeGa₃ reaction layer. The film on the annealed samples with an alpha-ferrite microstructure exhibited high porosity and a surface roughness of 1.97 Ra. In contrast, the film on the decarburised samples with a ferritic microstructure showed minimal porosity and a lower surface roughness of 1.29 Ra. Nanoindentation tests revealed Young modulus values of 231 GPa and 242 GPa and hardness values of 11.4 GPa and 12.7 GPa for the annealed and decarburised samples, respectively. The high porosity in the annealed samples is attributed to the suppression of FeGa₃ formation in regions containing chromium carbides. Shear stress for fracture, measured by microcantilever tests at the interface between the substrate and the inner matrix of the surface film, showed lower fracture shear stress in the annealed sample, attributed to the presence of larger pores within its microstructure. Full article

This study evaluates adhesive bolts (chemical anchors) bonded with epoxy and vinyl ester resins for surface and tunnel excavations in tropical mining environments under static and dynamic loading. Over 300 pull-out tests in concrete and hard rock examined the effects of bolt length, curing time, and substrate condition on load capacity, failure mode, and bond–slip response. Epoxy anchors exhibited higher bond strength, including under early-age and thermally active conditions, while vinyl ester showed improved ductility and post-peak behaviour in fractured rock. Numerical modelling with Rocscience RS2 (Phase 2) and Unwedge simulated excavation responses for bolt lengths of 190–250 mm and spacings of 0.5–2.0 m. Tensile failure dominated at wider spacings, whereas closely spaced anchors enhanced confinement and redistributed stresses. The combined experimental–numerical evidence quantifies chemical-anchor performance in complex subsurface settings and supports their use for early-age support and long-term stability. Findings motivate integration of resin-grouted bolts into modern support designs, particularly in seismically sensitive or hydrothermally variable mines. Full article

This study was conducted to evaluate the high-temperature protection performance of new hard coating systems. Woka 7202 (Cr₃C₂-NiCr) and Diamalloy 2002 (WC-NiCrFeBSiC) powders were coated onto 316L stainless steel substrates using the atmospheric plasma spraying (APS) method and subjected to isothermal oxidation (5–100 h) and hot corrosion (55% V₂O₅ + 45% Na₂SO₄, 1–5 h) tests. Although the coatings exhibited a laminar microstructure and some pores, cracks, and oxide-containing regions, they did not show any flaking or structural integrity deformations during the tests. Microstructural changes, oxide layer morphology, and the phases formed were examined in detail. The findings demonstrate that these coating systems not only provide chemical and structural stability against existing high-temperature environments, but also meet the requirements of next-generation thermal protection needs. In this regard, the study provides directly applicable information for the coating design and performance optimization for turbine blades, energy production equipment, and similar industrial components exposed to high-temperature oxidation and hot corrosion. Full article

Grey cast iron brake discs with lamellar graphite (GJL) offer excellent strength and thermal conductivity but are prone to wear and dust emissions. To mitigate these issues, a multilayer coating was applied via Laser Metal Deposition (LMD), comprising a 316L stainless steel base layer and a WC-reinforced top layer. This study examines the microstructural evolution of the coatings under simulated thermomechanical and corrosive conditions using a brake shock corrosion test. Microstructural characterization was performed via Scanning Electron Microscopy (SEM) and Electron Backscatter Diffraction (EBSD), focusing on grain size, orientation, and texture before and after testing. EBSD analysis revealed significant grain coarsening, with sizes increasing from below 20 µm to 30–60 µm, and a shift toward <101> texture. Hardness measurements showed a reduction in the WC-reinforced layer from 478 HV to 432 HV and in the 316L base layer from 232 HV to 223 HV, confirming the influence of thermomechanical stress. SEM analysis revealed a transition from horizontal cracks—caused by residual stress during LMD—to vertical microcracks propagating from the substrate, activated by braking-induced loads. These findings provide insights into the microstructural response of LMD coatings under realistic service conditions and underscore the importance of grain boundary control in designing durable brake disc systems. Full article

Perovskite solar cells (PSCs) rarely report, on a single-device platform, concurrent gains in optoelectronic efficiency and buried-interface mechanical robustness—two prerequisites for flexible and roll-to-roll (R2R) integration. We engineered a nanoplate-structured fluorine-doped tin oxide (NP-FTO) front electrode that couples light management with three-dimensional interfacial anchoring, and we quantified both photovoltaic (PV) and nanomechanical metrics on the same device stack. Relative to planar FTO, the NP-FTO PSCs achieved PCE of up to 25.65%, with simultaneous improvements in Voc (to 1.196 V), Jsc (up to 26.35 mA cm⁻²), and FF (to 82.65%). Nanoindentation revealed a ~28% increase in reduced modulus and >70% higher hardness, accompanied by a ~32% reduction in maximum indentation depth, indicating enhanced load-bearing capacity consistent with the observed FF gains. The low-temperature, solution-compatible NP-FTO interface is amenable to R2R manufacturing and flexible substrates, offering a unified route to bridge high PCE with reinforced interfacial mechanics toward integration-ready perovskite modules. Full article

This study investigated how Ti6Al4V substrate topography affects the performance of diamond-like carbon (DLC) coatings. Substrates with four finishes (unpolished, #100, #400, #800 grit) were coated, and their morphology, wettability, bonding structure, mechanical properties, and biological response were examined. Characterization was performed using AFM, SEM, contact angle tests, Raman spectroscopy, and nanoindentation. Biocompatibility was evaluated with A549 epithelial cells. DLC deposition reduced roughness while partly preserving surface features. Increasing Ra was associated with lower surface free energy and ID/IG ratios. It also correlated with higher hardness and modulus, reflecting greater sp³ bonding. Biological results, however, indicated that surface organization was more decisive than Ra magnitude. The #100-grit surface, with aligned anisotropic grooves, supported uniform wetting, protein adsorption, and sustained proliferation. In contrast, the unpolished and smoother surfaces did not maintain long-term growth. These findings suggest that anisotropy, rather than Ra alone, plays a key role in optimizing DLC-coated Ti6Al4V implants. Full article

Water-resistant antifogging hard coatings possessing self-healing properties were successfully prepared by applying N,N-dimethylformamide solutions containing the mixtures of carboxy-functionalized polysilsesquioxane (PSQ-2C) with oligo(ethylene glycol)s (OEGs; n = 2–6 and n = 2–4) at the feed functional group ratios (carboxy groups in PSQ-2C/hydroxy groups in OEG) of 10:1 and 4:1, respectively, onto oxygen plasma–treated glass substrates, followed by heat drying, water immersion, and room-temperature drying. The formation of ester bonds in the resulting coatings, indicating the presence of a cross-linked structure, was confirmed via Fourier-transform infrared/attenuated total reflectance spectroscopy. Notably, the coating prepared using PSQ-2C and tetraethylene glycol (OEG; n = 4) at a feed functional group ratio of 10:1 demonstrated no peeling or dissolution even after water immersion for 1 h, and its surface hardness, which was evaluated via the pencil scratch test, was 4H. Additionally, when exposed to water vapor generated from warm water at 40 °C at a distance of 2 cm, the coating maintained transparency for up to 85 s, confirming its excellent antifogging performance. Finally, the coating exhibited self-healing properties, as evidenced by the disappearance of scratches induced by a 5H pencil when the coating was left standing at 25 °C and 30% relative humidity for 5 min. Full article

The application of 7050 aluminum alloy in high-friction environments is limited due to its insufficient surface wear resistance. This study aims to enhance its wear resistance by depositing Cr/(Zr,Cr)N/(Zr,Cr,Al)N multilayer composite coatings using filtered cathodic vacuum arc deposition (FCVAD) technology under different Cr cathode arc currents (65A, 85A, 105A, 125A). Coatings were characterized by SEM, EDS, XRD, nanoindentation, and reciprocating wear testing. Results show that increasing arc current from 65 A to 125 A led to grain coarsening, reduced Zr content, and increased Cr-rich microdroplets. Nanoindentation results indicated that the coating prepared under a 65 A current exhibited the best hardness (13.03 GPa) and elastic modulus (242.87 GPa), which is mainly attributed to the formation of fine grains and fewer surface defects under low current conditions. Reciprocating wear tests showed that the wear resistance of all coating samples was superior to that of the uncoated 7050 aluminum alloy substrate. At an arc current of 85 A, the best wear resistance was observed, combining a low wear rate (5.31 × 10⁻⁵ mm³) with good mechanical strength (hardness of 8.54 GPa). This study revealed the regulatory mechanism of Cr cathode arc current on the microstructure and performance of Cr/(Zr,Cr)N/(Zr,Cr,Al)N multi-layer composite coatings, providing a theoretical basis and experimental support for optimizing coating process parameters to enhance the wear resistance of aluminum alloy surfaces. Full article