Multilayer Coatings Research Articles

Control of Cell Adhesion and Growth on Polysaccharide-Based Multilayer Coatings by Incorporation of Graphene Oxide

Control of Cell Adhesion and Growth on Polysaccharide-Based Multilayer Coatings by Incorporation of Graphene Oxide

Surface modified molybdenum disulfide nanosheets for corrosion resistance improvement on polyurethane coatings

Abstract Organic–inorganic hybrid coating has been applied on metallic corrosion protection effectively. Molybdenum disulfide (MoS2) nanosheets with graphene-like two-dimensional lamellar structure were an anticorrosion inorganic additive, rendering the organic coating better corrosion resistant. However, the aggregation and poor solubility are still current issues that should be addressed. Functionalization MoS2 nanosheets with surface modified by polydopamine (PDA) and silane coupling agent (KH560) were prepared in polyurethane (PU) composite coatings to obtain dense and intact multilayer network structure coatings for corrosion protection. KH560-PDA-MoS2/PU coating with crosslinked polymer network structure has a high impedance modulus, large contact angle, and strong hydrophobicity. The coating meets the national technical standards for salt spray testing and nitric acid (HNO3) titration testing, demonstrating excellent corrosion resistance.

Irradiation-decelerated corrosion behavior of CrN/TiSiN multilayer coating in Liquid Pb-Bi eutectic alloy

CrN/TiSiN multilayer coatings deposited at 316L substrate were selected to explore the effects of irradiation on LBE (Liquid Pb-Bi eutectic alloy) corrosion. The as-deposited and irradiated coatings were exposed in LBE. After exposure, all CrN/TiSiN coatings presented oxidation accompanied with PbBi penetration. Irradiated coatings revealed better corrosion resistance with thinner oxide layer and smaller penetration thickness. The largest decrement of 39% in oxidation thickness was observed in CrN/TiSiN deposited with Ti80Si20 under 150V. The irradiation-decelerated LBE corrosion could be attributed to the rapidly formed protective oxide layer resulting from the irradiation defects which accelerated nucleation and diffusion process during oxides formation. The decelerated effect was relatively weak in coatings deposited with a bias voltage under 100 V, in which the decrement is under 10%. The enhanced corrosion resistance was attributed to the quickly formed dense and continuous chromium oxide which rapidly formed due to the irradiation induced defects and acted as diffusion barrier to slow down LBE penetration.

Nodular defects aggravated tribocorrosion failure mechanism in Cr/GLC multilayer coatings for marine applications

Amorphous carbon coatings by various physical vapor deposition (PVD) have been widely attempted for enhancing both anti-wear and corrosion resistance of bulk materials used in harsh marine environments. However, PVD coatings are apt to be worn due to the existence of growth defects mostly like macro-size nodular particles. In this work, we deliberately fabricated the SiO2 nanoparticles with a size of 200 nm as nodular defects in Cr and graphite-like carbon (Cr/GLC) multilayer coatings, and the dependence of tribocorrosion behavior of coating on the nodular defects was focused by the comprehensively tribological and electrochemical tests. The results showed that introducing SiO2 nodular particles could not degrade the mechanical properties of Cr/GLC coating, but significantly accelerated both the abrasive wear in early sliding-stage under dry friction and the corrosive failure in chloride solution. Particularly, once the tribocorrosion tests in 3.5 wt.% NaCl solution were conducted for the Cr/GLC coating with nodular defects, the distinct ploughing damage originated from abrasive wear promoted the localized spallation of coatings, which thereafter enabled the easy water wedging along spallation for the substantial catastrophe of coatings. The present observations could evident the importance to fabricate the defect-free protective coatings required for harsh tribocorrosion applications.

Enhanced Long-Term Corrosion Resistance of 316L Stainless Steel by Multilayer Amorphous Carbon Coatings.

Diamond-like carbon (DLC) coatings are effective in protecting the key components of marine equipment and can greatly improve their short-term performance (1.5~4.5 h). However, the lack of investigation into their long-term (more than 200 h) performance cannot meet the service life requirements of marine equipment. Here, three multilayered DLC coatings, namely Ti/DLC, TiCx/DLC, and Ti-TiCx/DLC, were prepared, and their long-term corrosion resistance was investigated. Results showed that the corrosion current density of all DLC coatings was reduced by 1-2 orders of magnitude compared with bare 316L stainless steel (316Lss). Moreover, under long-term (63 days) immersion in a 3.5 wt.% NaCl solution, all DLC coatings could provide excellent long-term corrosion protection for 316Lss, and Ti-TiCx/DLC depicted the best corrosion resistance; the polarization resistances remained at ~3.0 × 107 Ω·cm2 after immersion for 63 days, with more interfaces to hinder the penetration of the corrosive media. Meanwhile, during neutral salt spray (3000 h), the corrosion resistance of Ti/DLC and TiCx/DLC coatings showed a certain degree of improvement because the insoluble corrosion products at the defects blocked the subsequent corrosion. This study can provide a route to designing amorphous carbon protective coatings for long-term marine applications in different environments.

Al3+ diffusion-directed assembly of GO-CNTs multi-layered composite coatings: Preparation and tribological performance

To resolve graphene coating's typical problems in tribological applications, including poor interfacial bonding, agglomeration, and low wear resistance, a dimensionally composited coating based on graphene oxide (GO) and carbon nanotubes (CNTs) was successfully prepared by a feasible metal-ion diffusion-directed assembly method. Experiments showed that the Al3+ diffusion-directed assembly method could significantly increase the coating interfacial binding strength, elasticity modulus, and hardness. In addition, the synergistic lubrication of GO and CNTs during friction enabled the Al3+-GO-CNTs5.0 coating to sustain a longer operation duration of 12,900 cycles. This study refers to inducing coordination with metal ions in various valence states and compositing carbon-based nanomaterials in different dimensions, which provides a feasible way to improve the lubricating coating's mechanical and tribological performances.

Tailoring the Reaction Path: External Crack Initiation in Reactive Al/Ni Multilayers

The influence of intentionally externally induced cracks in reactive Al/Ni multilayer systems is investigated. These cracks affect the reaction dynamics and enable tailoring of the reaction path and the overall velocity of the reaction front. The influence of layer variations onto mechanical crack formation and resulting reaction behavior are investigated. High‐speed camera imaging shows the meandering propagation of the reaction front along the crack paths. Therefore, the mechanical cracking process significantly changes the total velocity of the reaction front and thus offers a possibility to control the self‐propagating high‐temperature synthesis process. It is shown that the phase formation remains unaffected despite the applied strains and cracks. This favorable stability in phase formation ensures predictability and provides insight into the adaptation of RMS for precision applications in joints. The results expand the understanding of mechanical cracking as a tool to influence high‐temperature synthesis in reactive multilayer coatings and provide an opportunity to expand the range of applications.

Dual in-situ observation of tribochemical and morphological evolution of single-layer WS2 and multi-layer WS2/C coatings

AbstractThe outstanding tribological performance of transition metal dichalcogenides (TMDs) is attributed to their unique sandwich microstructure and low interlayer shear stress. This advantageous structure allows TMDs to demonstrate exceptional friction reduction properties. Furthermore, the incorporation of TMDs and amorphous carbon (a-C) in multi-layer structures shows excellent potential for further enhancing tribological and anti-oxidation properties. Amorphous carbon, known for its high ductility, chemical inertness, and excellent wear resistance, significantly contributes to the overall performance of these multi-layer coatings. To gain an in-depth understanding of the tribological mechanism and evolution of TMDs’ multi-layer coatings, a dual in-situ analysis was carried out using a tribometer equipped with a 3D laser microscope and a Raman spectrometer. This innovative approach allowed for a comprehensive evolution of the tribological, topographical, and tribochemical characteristics of both single-layer WS2 and multi-layer WS2/C coatings in real time. The findings from the dual in-situ tribotest revealed distinct failure characteristics between the single-layer WS2 coating and the multi-layer WS2/C coating. The single-layer WS2 coating predominantly experienced failure due to mechanical removal, whereas a combination of mechanical removal and tribochemistry primarily influenced the failure of the multi-layer WS2/C coating. The tribological evolution process of these two coatings can be classified into four stages on the basis of their tribological behavior: the running-in stage, stable friction stage, re-deposition stage, and lubrication failure stage. Each stage represents a distinct phase in the tribological behavior of the coatings and contributes to our understanding of their behavior during sliding.

Multifunctional coatings for solar module glass

AbstractCurrently, single‐layer antireflection coated (SLARC) solar glass has a dominant market share of 95% compared to glass with other coatings or no coating, for Si PV modules. This antireflection coating (ARC) results in an efficiency gain of 2–3%. However, there are issues with these SLARCs: (1) solar cell warming due to increased sub‐bandgap light absorption (by +0.4 ~ 1.2 K), counteracting the cell current gain and accelerating the aging of the solar panels, and (2) poor durability due to the coating's porous structure (typically lasting ≤5 years). This paper aims to develop a non‐porous multilayer coating (MLC) that is more durable and will act as a spectrally selective filter for solar modules. Studies have been conducted on MLCs in terms of optical, microstructure, mechanical, and durability properties compared with commercial single‐layer AR coatings. The MLCs showed superior performance in durability and benefit in reducing parasitic heat absorption in the non‐usable wavelength range. Also, a techno‐economic analysis model based on the multifunctional coating specifically to evaluate economic benefits has been developed.

Solid lubrication performance of multi-layered V2CTx coatings

MXenes induce excellent wear resistance under solid lubrication due to their distinctive surface chemistry, easy-to-shear ability, and capability to form low-friction and wear-resistant tribofilms. However, beyond the extensively studied Ti3C2Tx, other promising members of the MXene family remain largely underexplored. Therefore, we spray-coated multi-layer vanadium carbide (V2CTx) coatings (thickness ∼10.8 μm) on steel substrates and studied their tribological performance for prolonged times (10,000 cycles) using a reciprocating ball-on-disk tribometer with acting contact pressure of 445 MPa in ambient conditions. Results show that V2CTx-coated substrates demonstrate an 8-fold reduction in friction (COF of 0.11) and a 10-fold wear rate reduction (1.405 × 10−6 mm3 N−1 m−1). High-resolution materials characterization confirmed that the remarkable tribological performance of these coatings can be traced back to the formation of protective films on the substrate (tribofilm) and counterbody (transferfilm) consisting of contact pressure and frictional heat-induced degraded, deformed, exfoliated V2CTx nanosheets, nanocrystalline oxides, and amorphous carbon debris. This work fully elucidates the tribological potential of V2CTx, which is of utmost relevance for designing high-performance lubricating materials. Our work has assessed the performance of multi-layer V2CTx (M2XTx) due to its remarkable thermal stability, low molecular weight, good mechanical properties, and high interlayer spacing, thus serving as an entry point into diverse MXene compositions, including M4X3Tx (V4C3Tx).

Photoilluminated Redox-Processed Rh2P Nanoparticles on Photocathodes for Stable Hydrogen Production in Acidic Environments.

While photoelectrochemical (PEC) cells show promise for solar-driven green hydrogen production, exploration of various light-absorbing multilayer coatings has yet to significantly enhance their hydrogen generation efficiency. Acidic conditions can enhance the hydrogen evolution reaction (HER) kinetics and reduce overpotential losses. However, prolonged acidic exposure deactivates noble metal electrocatalysts, hindering their long-term stability. Progress requires addressing catalyst degradation to enable stable, efficient, and acidic PEC cells. Here, we proposed a process design based on the photoilluminated redox deposition (PRoD) approach. We use this to grow crystalline Rh2P nanoparticles (NPs) with a size of 5-10 on 30 nm-thick TiO2, without annealing. Atomically precise reaction control was performed by using several cyclic voltammetry cycles coincident with light irradiation to create a system with optimal catalytic activity. The optimized photocathode, composed of Rh2P/TiO2/Al-ZnO/Cu2O/Sb-Cu2O/ITO, achieved an excellent photocurrent density of 8.2 mA cm-2 at 0 VRHE and a durable water-splitting reaction in a strong acidic solution. Specifically, the Rh2P-loaded photocathode exhibited a 5.3-fold enhancement in mass activity compared to that utilizing just a Rh catalyst. Furthermore, in situ scanning transmission electron microscopy (STEM) was performed to observe the real-time growth process of Rh2P NPs in a liquid cell.

Heat Transfer Modelling of Multilayer Coated Tools During Turning of H13 Hardened Steel: Analogous Coating Layer Approach

Heat Transfer Modelling of Multilayer Coated Tools During Turning of H13 Hardened Steel: Analogous Coating Layer Approach

Eco-friendly epoxidized Eucommia ulmoides gum based composite coating with enhanced super-hydrophobicity and corrosion resistance properties

Developing a green, non-toxic, and sustainable bio-based anticorrosive coating is significant for achieving the objective of "carbon reduction". In this study, superhydrophobic multilayer coatings based on epoxidized Eucommia ulmoides gum were prepared via a layer-by-layer assembly bottom-up approach, providing comprehensive protection for mild steel. The foundational layer, comprising the epoxidized Eucommia ulmoides gum/industrial lignin composite (EEUG-EHL), exhibited commendable adhesion, impermeability, and corrosion resistance. The intermediate layer was composed of 8-hydroxyquinoline/zeolitic imidazolate framework-8 (8HQ@ZIF-8) nanoparticles, which controlled the release of 8HQ through pH responsiveness and had self-healing properties. Employing a spraying method, a top layer with micro-nanostructured consisting of a modified ZIF-8 nanoparticle was created, inspired by the micro-nano structure observed in cicada wings. The multilayer coating exhibited remarkable super-hydrophobicity (contact angle > 150°, sliding angle < 5°), chemical stability, self-cleaning properties, and anti-fouling properties. Notably, the multilayer coating demonstrated exceptional corrosion resistance, maintaining an impedance modulus of 108 ohm cm2 (at 0.01 Hz) after immersion in a 3.5 wt% NaCl solution for 45 days. This work introduces a novel approach to enhance the corrosion protection of metal equipment, aligning with the "green development" strategy and holding significance in advancing marine anti-corrosion construction.

Evaluating the corrosion and tribological performance of nanostructured CrN/TiN and TiN/CrN configurations applied on 410 stainless steel

ABSTRACT This study aims to compare the corrosion and tribological performance of TiN/CrN and CrN/TiN nanostructured multi-layer coatings deposited through cathodic arc evaporation PVD on 410-grade stainless steel. Both coating configurations were available in smooth (polished) and rough states. For the deposition of multi-layer coatings, a middle layer containing Cr and CrN was deposited to the substrate, followed by alternating nanolayers of TiN and CrN. finally, an upper layer of either CrN or TiN was applied. The nanoindentation test revealed that the hardness, Young’s modulus, H/E, and H3/E2 ratios of the coating with a TiN upper layer were 5.57, 1.42, 3.86, and 85.39 times of the substrate, respectively. At the coating with CrN upper layer, these values were 4.04, 1.13, 3.53, and 51.68 times of the substrate, respectively. Results showed that increasing the H/E and H3/E2 ratios increased wear resistance. Wear rates of smooth and rough TiN coatings and smooth and rough CrN coatings were reduced by 86%, 99%, 53%, and 26%, respectively, compared to the substrate. Results of the corrosion test showed that the rough CrN coating had greater corrosion resistance than the coating with a TiN upper layer and the substrate due to its higher hydrophobicity.

Improving the Wear Resistance Properties of 7A04 Aluminum Alloy with Three Surface Modification Coatings

Multiple advantages, such as good formability, high specific strength, excellent thermal conductivity, and high corrosion resistance, enable aluminum alloy wide application in various fields; however, low surface hardness and poor wear resistance limit its further development. In this study, three surface modification coatings were successfully prepared on the surface of 7A04 aluminum alloy by microarc oxidation (MAO) and a combination of hard anodizing treatment (HA) and physical vapor deposition (PVD), named MAO, HA+W+DLC, and HA+Ti+ta-C, respectively. The microstructure, hardness, and tribological properties of the three coatings and the 7A04 aluminum alloy substrate were studied. The results show that the surface quality and hardness of the coated samples were higher than those of the 7A04 aluminum alloy and that the HA+Ti+ta-C coating possessed the highest hardness of 34.23 GPa. Moreover, the wear resistance of the two multilayer coatings was significantly improved during the ring-block wear tests under oil lubrication, exhibiting a wear rate of 1.51 × 10−7 mm3/N·m for HA+W+DLC and 1.36 × 10−7 mm3/N·m for HA+Ti+ta-C.

Effect of titanium interlayer configurations on residual stresses and performance of titanium/titanium nitride multilayer coatings

Multilayer coatings provide an effective measure to control and optimise of residual stresses, enhance coating adhesion, fracture toughness, wear and corrosion resistance of coating system. In this study, we designed and produced bi-layer and four-layer titanium/titanium nitride magnetron sputtered coating configurations by altering the position of the interlayer. The in-plane residual stresses in different coating configurations are measured by multiple peak grazing incidence X-ray diffraction techniques. Subsequently, the effect of different compressive residual stresses on adhesion, mechanical properties, wear and corrosion resistance of coatings are investigated. Results show that the position of interlayer in multilayer coating configuration has a great impact on relaxation of residual stresses. The residual stresses are relieved by 26% and 46% by lowering the position of titanium interlayer from 800 nm at the top to 1000 nm and 1200 nm, respectively. The nanoindentation hardness is decreased by 11% and 13%, respectively. The wear rate of multilayer coating having interlayer position at 800 and 1000 nm from the top is ≈ 23% lower compared to bilayer however it is increased by ≈ 50% when interlayer coatings position changed to 1200 nm from the top. The interposition of interlayer in multilayer coating configurations decreased the corrosion current density by ≈ 50%. All multilayer coatings including higher residual stresses show better adhesion to the substrate compared to bilayer coatings which shows severe delamination.

Simulation of TiN/Ti Multilayer Coating under the Impact of Multiple Particles Based on Cohesive Element

In order to investigate the damage behavior of TiN/Ti multilayer coating under multi-particle impact and the influence of impact angle on erosion resistance, the ABAQUS 2019 software and the cohesive element technology were used for simulation. The results showed that, during the impact process, the upper surface of the TiN layer that was directly below the impact center was mainly subjected to compressive stress, while the lower surface was subjected to tensile stress. At the impact contact edge, tensile stress appeared on the upper surface of the TiN layer, while compressive stress appeared on the lower surface. The increase in the number of impacts leads to an increase in the maximum S11 stress inside the coating and the maximum displacement of the impact center during the impact process. The plastic damage was greater at the locations with higher strain in the Ti sublayer. During the impact process, severe damage occurred in both the top TiN layer and interface areas, and material failure occurred in the impact area. The increase in impact angle leads to an increase in the plastic strain energy of the entire model after the impact and the maximum S11 stress inside the coating during the impact process.

Hydrogen-Induced Microstructure Changes in Zr/Nb Nanoscale Multilayer Structures

Zr/Nb nanoscale multilayer coatings (NMCs) were studied after hydrogenation in a gaseous environment at 400 °C. The hydrogen distribution and content were determined by pressure and hydrogenation time. Increasing the pressure from 0.2 to 2 MPa resulted in different hydrogen distribution within the Zr/Nb NMCs, while the concentration remained constant at 0.0150 ± 0.0015 wt. %. The hydrogen concentration increased from 0.0165 ± 0.001 to 0.0370 ± 0.0015 wt. % when the hydrogenation time was extended from 1 to 7 h. The δ-ZrH hydride phase was formed in the Zr layers with Zr crystals reorienting towards the [100] direction. The Nb(110) diffraction reflex shifted towards smaller angles and the interplanar distance in the niobium layers increased, indicating significant lateral compressive stresses. Despite an increase in pressure, the nanohardness and Young’s modulus of the Zr/Nb NMCs remained stable. Increasing the hydrogen concentration to 0.0370 ± 0.0015 wt. % resulted in a 40% increase in nanohardness. At this concentration, the relative values of the Doppler broadening variable energy positron annihilation spectroscopy (S/S0) increased above the initial level, indicating an increase in excess free volume due to hydrogen-induced defects and changes. However, the predominant positron capture center remained intact. The Zr/Nb NMCs with hydrogen content ranging from 0.0150 ± 0.0015 to 0.0180 ± 0.001 wt. % exhibited a decrease in the free volume probed by positrons, as demonstrated by the Doppler broadening variable energy positron annihilation spectroscopy. This was evidenced by opposite changes in S and W (S↓W↑). The microstructural changes are attributed to defect annihilation during hydrogen accumulation near interfaces with the formation of hydrogen–vacancy clusters and hydrides.

Enhanced solid particle erosion resistance of nanocrystalline Ni-W coatings through multilayer approach

Electrodeposited nanocrystalline Ni-W alloy coatings are projected as potential alternatives for hard chrome (HCr) coatings owing to their comparable hardness and superior corrosion resistance. However, the limited strain hardening ability of the nanocrystalline Ni-W coatings manifests in their poor resistance towards solid particle erosion involving a high strain-rate (>103 s−1) deformation. In the present study, a novel microstructural engineering strategy has been implemented to enhance the strain hardening ability of the nanocrystalline Ni-W coatings without compromising on their strength/hardness. Ni-W multilayer coatings composed of alternatively stacked soft (2.6 GPa) and hard (8.5 GPa) Ni-W layers were developed using the pulse reverse electrodeposition technique. Further, to investigate the effect of individual layer thickness (λ), multilayer coatings with different λ were deposited. Solid particle erosion testing using the angular SiO2 particles showed that the multilayer coatings (irrespective of λ) exhibit superior erosion resistance compared to the homogeneous nanocrystalline Ni-15W at both oblique (θ = 30°) and normal (θ = 90°) impact conditions. The post-erosion microstructural analysis of the multilayer coatings revealed that the hard Ni-W layers undergo uniform strain (ε > 50 %) without cracking due to the constrained co-deformation imposed by the surrounding soft Ni-W layers. Therefore, the enhanced erosion resistance of the multilayer coatings is attributed to the effective dissipation of impact energy through co-deformation of the individual hard and soft Ni-W layers.

Formation Mechanism of Ti–Si Multi-Layer Coatings on the Surface of Ti–6Al–4V Alloy

Titanium alloys are widely used in aerospace applications due to their high specific strength and exceptional corrosion resistance. In this study, a silicide coating with a multi-layer structure was designed and prepared via a pack cementation process to improve the high-temperature oxidation resistance of titanium alloy. A new theory based on the Le Chatelier’s principle is proposed to explain the generation mechanism of active Si atoms. Taking the chemical potential as a bridge, a functional model of the relationship between the diffusion driving force and the change in the Gibbs free energy of reaction diffusion is established. Experimental results indicate that the depth of the silicide coating increases with the siliconization temperature (1000–1100 °C) and time (0–5 h). The multi-layer coating prepared at 1075 °C for 3 h exhibits a thick and dense structure with a thickness of 23.52 μm. This coating consists of an outer layer of TiSi2 (9.40 μm), a middle layer of TiSi (3.36 μm), and an inner layer of Ti5Si3 (10.76 μm). Under this preparation parameter, increasing the temperature or prolonging the holding time will cause the outward diffusion flux of atoms in the substrate to be much larger than the diffusion flux of silicon atoms to the substrate, thus forming pores in the coating. The calculated value of the diffusion driving force FTiSi = 2.012S is significantly smaller than that of FTiSi2 = 13.120S and FTi5Si3 = 14.552S, which perfectly reveals the relationship between the thickness of each layer in the Ti–Si multi-layer coating.