Ceramic Coatings Research Articles

Hierarchically Structured Ceramic Coatings Based on Zirconia and Magnesium Oxide with High Toughness

AbstractA major challenge in the application of ceramic materials is a trade‐off between strength and toughness. In this work, hierarchically structured ceramic coatings (HSCCs) are fabricated to address this challenge. HSCCs feature a dual‐layer micron‐scale structure built on a “brick‐mortar” nanoscale structure, which is achieved by changing the crystalline and amorphous phase ratio during plasma electrolytic oxidation (PEO). It is found that HSCCs with homogeneous interfaces exhibit high thermal stability up to 700 °C and a 65% improvement in shear strain resistance compared to conventional crystalline coatings (CCCs). This improvement is attributed to the stabilizing effect of atoms on the boundaries of the enhancement phase and the facilitating effect on the deformation of the compliant phase. The hierarchical structure effectively leverages the plasticity of the compliant phase and the strength of the enhancement phase facilitated by the homogeneous interface. This work proposes a feasible approach for improving the toughness of ceramic functional composites and mitigating their susceptibility to brittle fracture.

Tribological Properties of 7A04 Aluminum Alloy Enhanced by Ceramic Coating

The 7A04 Al alloy is a commonly used lightweight metal material; however, its low wear resistance limits its application. In this study, the wear resistance of this alloy was improved by preparing micro-arc oxidation (MAO) coatings, MAO/MoS2 composite coatings, and hard-anodized (HA) coatings on its surface. The friction and wear behaviors of these three coatings with diamond-like coated (DLC) rings under oil lubrication conditions were investigated using a ring–block friction tester. The wear rates of the coatings on the block surfaces were determined using laser confocal microscopy, and the wear trajectories of the coatings were examined using scanning electron microscopy. The results indicated that, among the three coatings, the MAO/MoS2 coating had the lowest coefficient of friction of 0.059, whereas the HA coating had the lowest wear rate of 1.47 × 10−6 mm/Nm. The MAO/MoS2 coatings exhibited excellent antifriction properties compared to the other coatings, whereas the HA coatings exhibited excellent anti-wear properties. The porous structure of the MAO coatings stored lubricant and replenished the lubrication film under oil lubrication. Meanwhile, the introduced MoS2 enhanced the densification of the coating and functioned as a solid lubricant. The HA coating exhibited good wear resistance owing to the dense structure of the amorphous-phase aluminum oxide. The mechanisms of abrasive and adhesive wear of the coatings under oil lubrication conditions and the optimization of the tribological properties by the solid–liquid synergistic lubrication effect were investigated. This study provides an effective method for the surface modification of Al alloys with potential applications in the aerospace and automotive industries.

Influence of Detonation Spraying Parameters on the Microstructure and Mechanical Properties of Hydroxyapatite Coatings

The process of osteointegration depends significantly on the surface roughness, structure, chemical composition, and mechanical characteristics of the coating. In this regard, an important direction in the development of medical materials is the development of new techniques of surface modification and the creation of bioactive ceramic coatings. Calcium-phosphate materials based on hydroxyapatite have been proposed as bioactive ceramic coatings on titanium implants for the effective acceleration of bone tissue healing. To obtain bioactive ceramic coatings, pulse power sources are best suited, namely detonation spraying, in which the energy of the explosion of gas mixtures is used as a source of pulse action. The pulse mode of operation in the detonation spraying method is preferable for the formation of bioactive ceramic coatings. It provides a high velocity of hydroxyapatite particles, which promotes their effective fixation on the titanium substrate, while minimizing the heating of the material. This approach preserves the substrate structure and improves the coating adhesion. Four different types of coatings with varying O2/C2H2 molar ratios, ranging from 2.6 to 3.7, were obtained using detonation spraying. Powders and obtained coatings of hydroxyapatite were studied by Raman spectroscopy and XRD structural analysis. The results of XRD phase analysis showed the partial conversion of the hydroxyapatite phase to the α-tricalcium phosphate (α-TCP) phase during the detonation spraying process. The results obtained by Raman spectroscopy indicate that hydroxyapatite is the main phase in coatings. All hydroxyapatite-based coatings exhibited hydrophobic properties, which was confirmed by contact-angle values above 90° in wettability tests, characteristic of hydrophobic surfaces. The adhesive strength of the coatings was measured by the scratch test method. Tribological tests were conducted using the ball-on-disk method under both dry conditions and in Ringer’s solution. This approach enabled the evaluation of wear resistance and friction coefficient of the coatings in different environments, simulating both lubrication-free conditions and those resembling physiological environments.

Multi-scale structure and reinforcement mechanisms of multi-element composite ceramic coatings

Multi-scale structure and reinforcement mechanisms of multi-element composite ceramic coatings

Development of Test Stand for High Temperature Abradability Test of Ceramic Coating for Turbine Shroud

Development of Test Stand for High Temperature Abradability Test of Ceramic Coating for Turbine Shroud

Advanced corrosion-resistant materials for enhanced nuclear fuel performance: A conceptual review of innovations in fuel cladding against molten salt degradation

The increasing demand for efficient and sustainable nuclear power has led to the development of advanced corrosion-resistant materials that can significantly enhance nuclear fuel performance. This conceptual review focuses on the innovations in fuel cladding materials designed to resist degradation in molten salt environments, which are crucial for advanced nuclear reactors like molten salt reactors (MSRs). Fuel cladding serves as a critical barrier between the nuclear fuel and the reactor environment, and its ability to withstand extreme temperatures and corrosive conditions is essential for safe and efficient reactor operation. Recent advancements in materials science have introduced novel alloys and coatings that demonstrate superior corrosion resistance in molten salts, which are used as both coolants and fuel solvents in MSRs. These innovations include high-temperature nickel-based alloys, refractory metals, and ceramic coatings, which are engineered to reduce the effects of molten salt corrosion, such as oxidation, pitting, and embrittlement. By enhancing the durability of fuel cladding, these materials contribute to improved fuel performance, longer reactor lifespans, and increased safety. This review explores key developments in corrosion-resistant materials, emphasizing the mechanisms by which these materials mitigate molten salt degradation. Additionally, it highlights the challenges associated with material selection, fabrication, and long-term performance in the highly corrosive environments of advanced nuclear reactors. Ongoing research into these materials offers promising avenues for the future of nuclear energy, particularly in addressing the limitations of current fuel cladding technologies. In conclusion, the use of advanced corrosion-resistant materials represents a significant step toward enhancing the performance and safety of nuclear fuel, ensuring the viability of MSRs and other advanced reactor designs. Continued innovation in this field is essential for the future of nuclear power.

Characterization and Performance Analysis of TiO<sub>2</sub> Coated UHMWPE for Biomedical Applications

Ultra-high Molecular Weight Polyethylene (UHMWPE) is a highly versatile polymer known for its exceptional mechanical properties, however, its limited life as an implant material for Total Joint Replacement (TJR) necessitates surface modification to extend its lifespan. This study aims to enhance the surface properties of UHMWPE through application of ceramic coatings. Magnetron sputtering method was used to deposit thin film of white Titania (TiO2) on the material’s surface. To evaluate the surface characteristics, such as surface roughness, uniformity and structure, coated and uncoated samples were analyzed through Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and X-ray Diffraction Analysis (XRD). The material performance in relation to biological context was investigated through Contact Angle measurement. A comparative analysis of coated and uncoated samples was then performed. The coated samples showed better wettability compared to uncoated sample. This fact highlights the hydrophilic nature of film. The results of the coated UHMWPE suggest that this surface modification technique could significantly extend the lifespan of UHMWPE implants in TJR, potentially addressing the current limitations associated with their longevity.

Delaminated structure of Zn-doped TiO2 coatings induced by ultrasound-auxiliary micro-arc oxidation: the influence of ultrasonic power

In this study, two representative ultrasonic vibration (UV) methods were employed to fabricate Zn-doped TiO2 micro-arc oxidation (MAO) ceramic coatings with enhanced corrosion resistance on pure Ti substrate. On the one hand, the surface morphology and chemistry of the coatings are characterized as partially crystallized hydroxyapatite nanoparticles and amorphous bands rich in Ca, P, Zn, and O. On the other hand, the MAO-modified coatings exhibit much greater corrosion resistance than the bare Ti surfaces, showing a reduction in corrosion current density (icorr) by at least an order of magnitude. However, a key finding is that a lower UV power setting of 360 V (named as the TZ-optimized protocols here) surpasses the higher 900 V (named as the TZ-powerful protocols) in terms of corrosion resistance (i.e. icorr =∼1.47×10−8 A/cm2 vs ∼7.85×10−7 A/cm2, respectively) as well as adhesion strength to the substrate (the critical load of ∼6.4 N vs ∼2.9 N, respectively), which can be attributed to the delaminated structure formed at higher UV powers. This work is expected to remind the potential side effect of such delamination in ceramic coatings produced by UV-assisted MAO processes on Ti-based alloys.

Protection of 316L Steel Against LBE Corrosion by a CaO-MgO-Al2O3-SiO2 Glass–Ceramic Coating

A CaO-MgO-Al2O3-SiO2 glass–ceramic coating was prepared by the slurry method and subsequent sintering to improve the corrosion resistance of 316L steel in liquid lead–bismuth eutectic alloy at high temperatures. The glass–ceramic coating, sintered at 884 °C, was dense and demonstrated strong adhesion to the substrate. It was composed of the crystalline phases diopside (CaMgSi2O6) and anorthite (CaAl2Si2O8) and had an average Vickers hardness of 595 HV, which was over three times that of 316L steel. After corrosion in an oxygen-saturated, static lead–bismuth eutectic alloy at 500 °C for 1000 h, the uncoated 316L experienced significant mass gain (0.04 g) due to severe oxidative corrosion, resulting in the formation of Fe3O4 and Pb2O on its surface. In contrast, the glass–ceramic-coated specimens showed a very small mass gain (0.0012 g) after corrosion. The coating maintained good thermal stability; its crystalline phase composition remained largely unchanged after the corrosion test. The glass–ceramic coating still exhibited dense microstructure and tightly adhered to the substrate after corrosion. There was no evident penetration of lead–bismuth into the coating, and no dissolution of the coating’s elements into the lead–bismuth alloy was detected. These observations confirm that the glass–ceramic coating possessed superior corrosion resistance in liquid lead–bismuth eutectic environments.

Effect of Artificial Saliva Modification on Corrosion Resistance of Metal Oxide Coatings on Co-Cr-Mo Dental Alloy

Surface modifications not only improve the corrosion resistance of Co-Cr-Mo dental alloys (Bego Wirobond® C) but also ensure their long-term performance and reliability in dental applications. This paper describes the preparation of single-layer TiO2-ZrO2 sol–gel coatings on the Co-Cr-Mo dental alloy using the method of dip-coating. The TiO2-ZrO2 sol–gel coatings were sintered at 300 and 500 °. SEM analysis shows that sintering at 300 °C produces a uniform, slightly dense structure without micro-cracks, while sintering at 500 °C results in a denser structure with micro-cracks due to higher stress and shrinkage. EDS confirms that sintering temperature affects the elemental composition of the coating, with higher temperatures causing the volatilization or diffusion of Ti and Zr. Roughness measurements indicate that the Ra value increases with the sintering temperature, meeting dental application requirements. Electrochemical measurements by open-circuit potential, EIS, and cyclic potentiodynamic curves demonstrate that sintering temperature and saliva composition affect corrosion resistance, with NaF and mouthwashes (Listerine Total Care Teeth Protection® and Meridol®) generally increasing charge transfer resistance and double-layer capacitance. The ceramic TiO2-ZrO2 coatings significantly reduce pitting corrosion susceptibility at physiological and acidic pH, with the 500 °C sintered coating showing better protective properties. These findings highlight the potential of TiO2-ZrO2 coatings in enhancing the performance of Co-Cr-Mo dental alloys.

Microstructure and properties behavior of in situ synthesized with high content (Ti, W) C reinforced In625 by two step-laser direct energy deposition

The formation of sensitive interface cracks and the difficulty in processing high-concentration Ni-based ceramic coatings via direct energy deposition (LDED) present major engineering challenges. To address these, high-quality In625/ceramic coatings with various mass contents of Ti, nickel-coated graphite (Ni3C), and WC were fabricated on QT250 using two-step laser directed energy deposition (TsLDED). The influence of the Ti/C: WC molar mass ratio on the bonding interface, microstructure, phase composition, and mechanical properties of the coatings was analyzed. The results indicated that grains at the In625/ceramic coating interface formed epitaxial growth, ensuring a robust bond. In situ synthesis of (Ti, W) C, WCx (WC and W2C), M23C6, and other precipitated phases were uniformly distributed, enhancing nucleation, refining microstructure, and improving mechanical properties. The addition of Ti facilitated the transformation of WCx to (Ti, W) C. High Ti and C concentrations promoted eutectic structure formation in the matrix phase, enhancing performance. The In625 + 56 % Ti – 14 % Ni3C – 30 % WC composite coating exhibited the highest microhardness and the lowest friction coefficient, with microhardness 5.61 and 3.6 times that of QT250 and In625 coatings, respectively, and a friction coefficient 0.3 times that of In625. Variations in the Ti/C: WC molar mass ratio directly affected the content, proportion, and type of (Ti, W) C, WCx, γ-Ni, and eutectic structures comprising M23C6, NiTix, Ni2W4C, Cr2Ti, and γ-Ni, influencing microstructure evolution and mechanical properties. The TsLDED process thus enables the preparation of In625/ceramic reinforced coatings with improved mechanical properties.

Effect of non-contact induction heating on HA coatings and bone cement, an ex vivo study

Background Prosthetic joint infection is a serious complication that can arise after total joint replacement surgery. When bacteria colonise an orthopaedic implant, they form biofilms that protect them from their environment, making them difficult to remove. Treatment is further complicated by a global rise of antimicrobial resistance. These protective mechanisms make treatment of prosthetic joint infection increasingly complex. Non-contact induction heating is an upcoming technology that uses heat to eradicate bacteria that are present on the surface of metallic implants. This study aims to provide insight into the feasibility of using non-contact induction heating on metallic implants that are in direct contact with other biomaterials, such as coatings composed of hydroxyapatite and bone cement composed of poly (methyl methacrylate) (PMMA). Methods Characterisation of hydroxyapatite coatings and adhesion strength tests were conducted according to standards set by the International Organisation for Standardisation (ISO 13779-2). The fixation strength of acrylic bone cement was tested according to an adapted method from ISO. Results It was found that non-contact induction heating did not significantly affect the adhesion strength of hydroxyapatite coatings. In contrast to hydroxyapatite coatings, acrylic bone cement softened temporarily as the temperature exceeded the glass transition temperature (83.38 ± 10.88°C). However, the induction heating temperature had no significant effect on the fixation strength after the cement was allowed to cool down. Conclusion This study shows the feasibility of using non-contact induction heating up to 80°C when bone cement or ceramic coatings are present in contact with infected metallic implants.

Effect of Current Density on the Wear Resistance of Ceramic Coatings Formed on 7075 Aluminum Alloy via Microarc Oxidation

Effect of Current Density on the Wear Resistance of Ceramic Coatings Formed on 7075 Aluminum Alloy via Microarc Oxidation

In vitro assessment of corrosion, antibacterial properties, and degradation behavior of zirconia-coated polyetheretherketone (PEEK)

The medical industry often uses ceramic and polymeric coatings to safeguard metal substrates. However, more investigation is required to explore the implementation of ceramic coatings on polymer substrates and to determine their degradation and in vitro characteristics. This work involves applying zirconia coating onto the 3D-printed PEEK polymer substrate using the RF magnetron sputtering technique. With varying layer thickness and printing speed parameters, PEEK samples (S1, S2, S3, and S4) were 3D printed and coated with zirconia. The coated and uncoated samples were immersed in Fusayama artificial saliva solution for 30 days. Following immersion in artificial saliva, this study examined the corrosion of 3D-printed PEEK samples with and without coatings. Elemental mapping, field emission scanning electron microscopy, and X-ray photoelectron spectroscopy were employed to evaluate sample morphology and estimate the binding energy of possible compounds generated in the artificial saliva solution. In vitro assessments such as antibacterial studies were performed against E. coli and S. aureus, and cytotoxic analysis was performed using Human Wharton’s jelly-derived mesenchymal stem cells (WJ-MSCs) to determine cell proliferation. The results indicated that sample S3, printed with 0.15 mm layer thickness and 20 mm/s print speed coated with zirconia showed a better degradation rate of 9.01% whereas the other three samples S1, S2, and S4 coated with zirconia showed deterioration rates of 36.4%, 33% and 16% respectively. Sample S3 showed a better antibacterial activity as biofilm formation was absent and also showed cell viability of about 79% and hence can be considered as a viable option for dental applications.

PROCESSO DE APLICAÇÃO NO ASSENTAMENTO DAS PEÇAS EM CERÂMICAS

This study aims to explore the process of applying ceramic tiles, with a special focus on ceramic coatings used in high humidity environments, such as bathrooms and kitchens. The main objective is to deepen knowledge in the area of ​​ceramic coatings, understanding their properties, performance and implications for the durability of residential buildings. To answer this question, a detailed bibliographic review will be carried out on the ceramic materials available on the market, their technical characteristics and behavior in the face of humidity. In addition, case studies and experiments will be analyzed to assess the efficiency of ceramic coatings in preventing problems such as infiltration, mold and premature wear. The research will also include an analysis of the thermal properties of ceramic materials to understand their contribution to the energy efficiency of buildings. The expected results of this study aim to provide practical guidelines for civil engineers in the correct selection and application of ceramic coatings in humid environments. The findings are expected to help increase the lifespan of residential buildings and promote more efficient use of energy resources.

The Effect of Shot Blasting Abrasive Particles on the Microstructure of Thermal Barrier Coatings Containing Ni-Based Superalloy

Grit particles remaining on the substrate surface after grit blasting are generally considered to impair the thermal performance of thermal barrier coatings (TBCs). However, the specific mechanisms by which these particles degrade the multilayer structure of TBCs during thermal cycling have not yet been fully elucidated. In this study, the superalloy substrate was grit-blasted using various processing parameters, followed by the deposition of thermal barrier coatings (TBCs) consisting of a metallic bond coat (BC) and a ceramic top coat (TC). After thermal shock tests, local thinning or discontinuities in the thermally grown oxide (TGO) layer were observed in TBCs where large grit particles were embedded at the BC/substrate interface. Moreover, cracks originated at the concave positions of the TGO layer and propagated vertically towards BC; these cracks may be associated with additional stress imposed by the foreign grit particles during thermal cycling. At the BC/substrate interface, crack origins were observed in the vicinity of large grit particles (~50 μm).

Synergism of h-BN and La2O3 in improving the tribological performance of Al2O3 coatings

Wear is a significant cause of material loss, contributing to surface degradation of crucial components, notably within engineering sectors. This article is dedicated to enhancing tribological properties through the implementation of Al2O3-based ceramic coatings, specifically targeting situations where reciprocating sliding wear predominates. This study introduces lanthanum oxide (La2O3), a rare earth oxide, as a reinforcing material in Al2O3 coatings in varying weight percentages of 1.2%, 1.6%, and 1.8% respectively along with 3% hexagonal boron nitride (h-BN). The coatings were developed by the high-velocity oxy-fuel (HVOF) surface modification technique, with SS304 serving as the substrate. The porosity, hardness, and chemical composition of the developed coatings were examined. Additionally, reciprocating tribological testing of the coatings was conducted at two loads (5 N and 15 N) under dry sliding conditions. Results indicated that coating containing 95.4% Al2O3–3% h-BN–1.6% La2O3 reduced the porosity up to 50% and improved hardness by 46% compared to the 97% Al2O3–3% h-BN coating. The formation of the α-Al2O3 phase leads to an increase in coating hardness and a reduction in porosity. Notably, the coating comprising 97% Al2O3–3% h-BN exhibited the lowest coefficient of friction among all developed coatings under both loads. Furthermore, an increase in load led to a decrease in the coefficient of friction for all developed coatings. Furthermore, the addition of La2O3 (1.6 wt%) to the coating with 3 wt% h-BN exhibited the lowest wear at both loads. The findings also revealed increased wear at high loads for all developed coatings. SEM, EDS, and XRD analysis of the worn surfaces revealed the contribution of h-BN and La2O3 in enhancing friction behavior through the formation of oxides such as α-Al2O3, B2O3, Al8B2O15, and Al11La0.497O17, along with alterations in wear mechanism and the size of wear debris. The composite coatings developed in this study shall be helpful in advanced engineering applications.

Corrosion resistance analysis of Al2O3-TiO2 composite ceramic coatings on carbon steel pipe surfaces

This study investigates the corrosion resistance of Al2O3-TiO2 composite coatings reinforced with multi-walled carbon nanotubes (MWCNTs) on carbon steel pipe surfaces. Coatings were deposited using atmospheric plasma spraying (APS) and high velocity oxy-fuel (HVOF) techniques. Microstructural analysis revealed that HVOF-sprayed coatings exhibited denser and more homogeneous structures compared to APS-sprayed coatings. Electrochemical tests in 3.5 wt% NaCl solution showed that the HVOF-sprayed Al2O3-13 wt% TiO2-1.5 wt% MWCNT coating demonstrated the lowest corrosion current density of 7.6 × 10−9 A/cm2 and the most positive corrosion potential. Hot corrosion tests in a simulated boiler environment (500°C, 1000 h) revealed that this coating also exhibited minimal weight gain (0.9 mg/cm2) and thickness loss (2 μm). The corrosion rate of the optimal coating was 0.05 mm/year, significantly lower than the bare carbon steel (2.45 mm/year). XRD analysis of corroded samples showed that HVOF-sprayed coatings maintained their original phase composition without detectable substrate corrosion products. The superior corrosion resistance of the HVOF-sprayed Al2O3-13 wt% TiO2-1.5 wt% MWCNT coating is attributed to its optimized composition, dense microstructure, and the reinforcing effect of MWCNTs. These findings provide valuable insights for developing advanced coating solutions to mitigate corrosion-related challenges in the oil and gas industry and other harsh industrial environments.

High‐temperature thermal conductivity measurement of porous ceramic coatings with a high heat flux CO2 laser rig

AbstractYttrium‐stabilized zirconia (YSZ) plays a crucial role in thermal barrier coatings widely used to protect metallic components in gas turbine engines against high‐temperature combustion product gases and harsh environments. The thermal conductivity of these coatings is a critical parameter influencing the gas turbine design, performance, and service life. In this study, a laser temperature gradient method is utilized to measure the thermal conductivity of porous YSZ coatings. The method employs specialized laser energy delivery to create a one‐dimensional temperature gradient through the sample thickness, closely simulating the operational condition. This approach provides an effective, direct means to determine the thermal conductivity of high‐temperature heat‐resistant porous ceramic materials.

Oxidation and ablation resistance of (TiZrHf)C medium-entropy ceramic coating on C/C composite constructed in-situ at low temperature down to 900°C

The low-cost construction of ultra-high temperature high/medium-entropy ceramic coatings is pivotal for advancing their engineering applications. The study successfully prepared (TiZrHf)C medium-entropy ceramic coatings on C/C composite surfaces using an in-situ molten salt disproportionation reaction at temperatures as low as 900°C. The (TiZrHf)C coatings, approximately 20 μm thick, showed uniform distribution of Ti, Zr, and Hf, typical of medium-entropy ceramics. The process entails Hf reducing Zr⁴⁺ and Ti⁴⁺ to divalent states, which then disproportionate and react with carbon to form the coatings. High-temperature oxidation tests revealed larger oxide grain sizes and dense boundaries in coatings with higher Ti content, indicating superior oxidation resistance. Additionally, ablation tests demonstrated that a suitable amount of liquid-phase TiO₂ formed on the composite surface improves ablation resistance by stabilizing the oxide layer. This cost-effective, highly designable method promotes medium/high-entropy ultra-high temperature ceramics' engineering application.