Ceramic Coatings Research Articles

Mechanism of Ag-SiO2-TiO2 Nanocomposite Coating Formation on NiTi Substrate for Enhanced Functionalization

The functionality of the NiTi shape memory alloy was improved through engineering Ag-SiO2-TiO2 nanocomposite coatings. For this purpose, an anaphoretic deposition process, conducted at a constant voltage of 40 V and deposition times ranging from 1 to 10 min, was used. Scanning electron microscopy (SEM) analysis demonstrated that the deposition parameters significantly impacted the morphology of the coatings. Complementary Raman Spectroscopy and X-ray diffraction (XRD) analyses confirmed the successful formation of distinct nanocomposite layers, and revealed the details of their crystalline structure and chemical composition. After that, the adhesion between the NiTi substrate and the electrophoretically deposited ceramic coatings was improved through a post-deposition heat treatment. To prevent excessive shrinkage and cracking of the coating, tests were carried out to characterize the behavior of the coating material at elevated temperatures. The nanocomposite coatings were exposed to a temperature of 800 °C for 2 h. The annealing induced significant structural and morphological transformations, resulting in layers that were distinctly different from both the original materials and those produced solely through electrophoretic deposition. The thermal treatment resulted in the formation of a new kind of nanocomposite structure with enhanced reactivity.

Silver-doped ZrO2-TiO2 nanocomposite coatings on 316L stainless steel for enhanced corrosion resistance and bio applications

The demand for ceramic based nanocomposite coatings has increased because they play a significant role in orthopedic implants and medical devices. Ceramic nanocomposites are inert and highly biocompatible, which improve corrosion resistance under physiological fluids. The ceramic nanocomposites were deposited (silver-doped ZrO2/TiO2) on SS 316L, and their biocompatibility, strength of adhesiveness, and corrosion resistance properties were studied. A detailed investigation of corrosion resistance, wettability, and biocompatibility concerning microstructures and the inclusion of silver as a dopant was conducted. The deposited films annealed at 600 °C display crystallinity with the coexistence of TiO2 rutile and ZrO2 monoclinic phases. The surface morphology shows the average particle size on thin film is around 40 to 45 nm. The deposited films show a decreased corrosion current density (ICorr) in potentiodynamic polarization curves, confirming the adequate protection against corrosion using simulated body fluid and phosphate buffer saline at 37±1 °C. The surface wettability of coatings is hydrophilic, and it improves in-vitro compatibility. The apatite growth in SBF solution on the implant surface predicts a favorable condition for bone regeneration in the patient's body. The effect of silver dopant on improving apatite growth on implant surface is also discussed. From electrochemical impedance spectroscopy, the diameter of the semicircle in the Nyquist plot shows more than bare metal; the higher the diameter indicates the more resistive behavior of deposited films, which shows the effective corrosion resistance in the electrolytic solution. It is found that the biocompatibility and corrosion resistance are improved compared with bare SS 316L. Hence, ceramic nanocomposite coatings show great potential in the orthopedic implant industry.

Porous Dielectric Structure and Response Speed of Moisture Sensors

Humidity sensors are typically made of alpha-alumina films as porous dielectric materials deposited through the anodic spark deposition (ASD) technique, a unique anodic oxidation method to deposit ceramic coatings on the exterior of metals. Close attention to the precise composition of electrolyte solution is crucial when mixing chemical compounds. Moreover, the ASD process, which happens during dielectric breakdown at the anode surface in an electrochemical cell, is clearly followed by visible sparking at the anode/electrolyte interface, leading to the formation of various ceramic coatings on metal substrates. Electrical breakdown happens over an anodized barrier layer, typically amorphous aluminum oxide, which has been produced on the metal anode. The local high temperature (>2000°C) produced by electrical sparks melts the amorphous aluminum oxide and converts it to alpha-aluminum oxide, forming the stable foundation for a reliable humidity sensor.In this study, we produced a variety number of small pores to investigate the response speed of moisture sensors. The ASD current can be adjusted to control the number of small pores. The smaller current gives a greater number of small pores. We focused on low-humidity sensors, often referred to as dew-point sensors. In fabrication of dew-point sensors, Scanning Electron Microscopy (SEM) was used to examine and determine the size of pores. Three different currents, 30 mA, 25 mA, and 10 mA, have been tried for comparative analysis of small pores existing within large pores. Two pores have been measured for current 10 mA, resulting in sizes of 47 nanometer (nm) and 71 nm, respectively. Similarly, three small pores for current 30 mA were measured with sizes of 32 nm, 42 nm, and 31 nm respectively. After the testing of low-humidity (dew-point) sensors, we found that the number of small pores does not significantly affect the response speed of the sensors.

Thick Columnar-Structured Thermal Barrier Coatings Using the Suspension Plasma Spray Process

Higher operating temperatures for gas turbine engines require highly durable thermal barrier coatings (TBCs) with improved insulation properties. A suspension plasma spray process (SPS) had been developed for the deposition of columnar-structured TBCs. SPS columnar TBCs are normally achieved at a short standoff distance (50.0 mm–75.0 mm), which is not practical when coating complex-shaped engine hardware since the plasma torch may collide with the components being sprayed. Therefore, it is critical to develop SPS columnar TBCs at longer standoff distances. In this work, a commercially available pressure-based suspension delivery system was used to deliver the suspension to the plasma jet, and a high-enthalpy TriplexPro-210 plasma torch was used for the SPS coating deposition. Suspension injection pressure was optimized to maximize the number of droplets injected into the hot plasma core and achieving the best particle-melting states and deposition efficiency. The highest deposition efficiency of 51% was achieved at 0.34 MPa injection pressure with a suspension flow rate of 31.0 g/min. With the optimized process parameters, 1000 μm thick columnar-structured SPS 8 wt% Y2O3-stabilized ZrO2 (8YSZ) TBCs were successfully developed at a standoff distance of 100.0 mm. The SPS TBCs have a columnar width between 100 μm and 300 μm with a porosity of ~22%. Furnace cycling tests at 1125 °C showed the SPS columnar TBCs had an average life of 1012 cycles, which is ~2.5 times that of reference air-plasma-sprayed dense vertically cracked TBCs with the same coating thickness. The superior durability of the SPS columnar TBCs can be attributed to the high-strain-tolerant microstructure. SEM cross-section characterization indicated the failure of the SPS TBCs occurred at the ceramic top coat and thermally grown oxide (TGO) interface.

Data-Driven Optimization of Plasma Electrolytic Oxidation (PEO) Coatings with Explainable Artificial Intelligence Insights

PEO constitutes a promising surface technology for the development of protective and functional ceramic coatings on lightweight alloys. Despite its interesting advantages, including enhanced wear and corrosion resistances and eco-friendliness, the industrial implementation of PEO technology is limited by its relatively high energy consumption. This study explores the development and optimization of novel PEO processes by means of machine learning (ML) to improve the coating thickness. For this purpose, ML models random forest and XGBoost were employed to predict the thickness of the developed PEO coatings based on the key process variables (frequency, current density, and electrolyte composition). The predictive performance was significantly improved by including the composition of the used electrolyte in the models. Furthermore, Shapley values identified the pulse frequency and the TiO2 concentration in the electrolyte as the most influential variables, with higher values leading to increased coating thickness. The residual analysis revealed a certain heteroscedasticity, which suggests the need for additional samples with high thickness to improve the accuracy of the model. This study reveals the potential of artificial intelligence (AI)-driven optimization in PEO processes, which could pave the way for more efficient and cost-effective industrial applications. The findings achieved further emphasize the significance of integrating interactions between variables, such as frequency and TiO2 concentration, into the design of processing operations.

Microstructure and high-temperature oxidation resistance of Ti-6Al-4V alloy with in-situ SiC-SiO2 nano-composite coating by LPDS technique

A SiC-SiO2 nano-composite coating was prepared via a novel liquid-phase plasma-assisted particle deposition and sintering (LPDS) method to enhance the oxidation resistance of the Ti-6Al-4V alloy. For comparison, a conventional plasma electrolytic oxidation (PEO) ceramic coating is fabricated on the Ti-6Al-4V alloy. The microstructure and formation mechanisms of both ceramic coatings were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The results indicated that the thickness of the SiC nano-composite coating (∼40 μm) increased significantly by 285 % compared to the PEO coating (∼14 μm). The microstructural evolution and isothermal oxidation performance of the PEO and SiC-SiO2 nano-composite coating were comparatively investigated at 800 °C. After 100 h, the thickness gain of the SiC-SiO2 nano-composite coating (∼14 μm) was lower than that of the PEO coating (∼26 μm). The improved oxidation performance is primarily attributed to the outermost layer containing abundant SiC nanoparticles, which transform into SiO2 during the oxidation process and effectively inhibiting the inward penetration of oxygen.

Spherical nanocrystalline ScYSZ thermal barrier material by a novel supersonic plasma spheroidization method: Simple synthesis and excellent performance

The performance of plasma sprayed thermal barrier coatings (TBCs) is strongly dependent on the quality of the feedstock powders, which usually are fabricated by conventional spray drying and multi-step sintering methods. In this work, a novel supersonic plasma spheroidization technology was employed to fabricate the spherical nanocrystalline Sc2O3-Y2O3 co-stabilized ZrO2 (ScYSZ) powder. The deformation process from the irregular powder to the spherical one was stimulated by the COMSOL phase field simulation. The results suggested that the original irregular pyrolysis products of ScYSZ precursors were aggregated into spherical powders by plasma spheroidization technology. The COMSOL simulations verified that the powder changed from irregular particles to spherical ones. The spheroidized ScYSZ particles exclusively consisted of non-transformed t’-ZrO2 phase and showed good fluidity, smooth surface and high apparent density, which were expected to have a broader application prospect in the field of TBCs and other ceramic coatings.

Oxidation failure behavior and repair of the damaged SiC-ZrB2/SiC coating of C/C composites

The impacts of damage on the thermal barrier performance of SiC-ZrB2/SiC coating of C/C composites were investigated. The microstructure, chemical components, and thermal protection performance of the damaged coating before and after repair were analyzed, and the failure behavior of the damaged coated C/C composites was studied. After oxidation at 1500 °C for 360 min, the weight loss of the undamaged sample was −0.38 %, while that of the damaged sample reached 21.16 %. A repair method using polysiloxane and SiC-ZrB2 powder as repair agent was employed to recover the oxidation resistance property of the damaged coating. The repair agent generated SiOC ceramics after high-temperature treatment, covering the damaged area and bonding well with the original coating. The weight loss of the repaired sample was 2.4 %, which was significantly improved compared to the damaged coating. This work offers a research foundation for the optimization of the repair of damaged silicon-based ceramic coatings.

Применение эволюционных и роевых методов для оптимизации многопараметрического управления процессом нанесения гальванического покрытия

One of the key parameters of the quality of ceramic coatings is its thickness, which must meet technical requirements and provide the necessary degree of corrosion protection, wear resistance and appearance of the coating. Ensuring the uniformity of the galvanic coating is one of the most important and complex tasks of high-tech machine-building production, for which a number of methods have been proposed, such as controlling current modes, the location of electrodes in the bath, and the electrolyte flow rate. However, in most cases, these methods require solving the problem of optimal multiparametric control. Prompt and accurate optimization when changing the conditions of electrolysis (electrode potentials, composition and properties of the electrolyte), as well as, if necessary, taking into account the multi-extreme nature of the dependence of the uniformity coefficient on the process parameters (current density, interelectrode distance, electrolyte flow rate) is a rather complex and ambiguous multifactorial task that limits the use of classical methods for- the claim of a global extreme. The article explores the possibility and expediency of using intelligent heuristic methods, such as evolutionary and swarm methods, to solve this problem. Objective. The objective of this study is to determine the effectiveness of using genetic algorithms and the particle swarm method to solve the problem of optimizing the multiparametric control of the electroplating process. Materials and methods. Methods of mathematical modeling, methods and software environment of numerical modeling and optimization were used to conduct the study. Results. The article investigates the effectiveness of the application of evolutionary and swarm optimization methods in relation to the process of applying chrome plating in a galvanic bath with many anodes with multiparametric control of current density, interelectrode distance and electrolyte flow rate. The best approximation to the extreme of the uniformity coefficient can be achieved by genetic algorithms using the mutation operation and the particle swarm method, while achieving the extreme using the particle swarm method is achieved in fewer iterations. Conclusion. The results of the study substantiate the expediency of using evolutionary and swarm methods to solve the problem of optimizing the multiparametric control of the electroplating process, while it is possible to increase the efficiency of these methods due to additional tuning.

Electric-field-dependent electrical properties and domain switching of 0.92BNT-0.08BT ceramic coatings

Bi0.5Na0.5TiO3-based ferroelectric materials with strong ferroelectricity and high Curie temperature have great application prospects in modern microdevices. In this paper, 0.92BNT-0.08BT ceramic coating was prepared by supersonic plasma spraying. The phase, microstructure, electrical properties and domain response of 0.92BNT-0.08BT ceramic coating were analyzed. The findings demonstrate that the 0.92BNT-0.08BT ceramic coating is without obvious structural defects and has a completely structure with good interface bonding. 0.92BNT-0.08BT ceramic coating has good electrical properties, the dielectric constant is 417, the dielectric loss is 0.3, and the remnant polarization is 16.6 μC/cm2. The piezoelectric force microscopy (PFM) results show that the 0.92BNT-0.08BT ceramic coating generally exhibits irregular and inhomogeneous striped nanodomains, with significant changes in amplitude and phase response under different electric fields. The results using switching spectroscopy-piezoresponse force microscopy (SS-PFM) show that the local piezoelectric coefficient (PRmax) of the 0.92BNT-0.08BT ceramic coating reaches 754.3 p.m./V at a voltage of 20 V, and the ferroelectric domains exhibit a clear switching behavior.

High temperature oxidation resistance and thermodynamic properties of (TaNbZr)N and (TaNbZr)C quaternary ceramic coating

A TaNbZr-based quaternary ceramic coating with a metallurgical transition layer on a titanium alloy surface has been produced. The quaternary ceramic coatings exhibit a face-centered cubic structure and distinct structural orientation. The introduction of carbon and nitrogen significantly improved high-temperature oxidation resistance compared to metallic coatings in cyclic oxidation tests. Specifically, the (TaNbZr)N coating provided effective thermal protection during 800 °C cyclic oxidation for 100 hours (10 cycles). The phase stability and evolution of quaternary ceramic coatings were clarified using in-situ XRD. Further, first-principles calculations elucidated the enhanced thermal stability and high-temperature performance of (TaNbZr)N and (TaNbZr)C coatings.

Application of Thermal Spraying Technology in Concrete Surface Ceramic-Based Coating

Enhancing the durability and extending the service life of concrete are crucial for promoting its sustainable development. Applying surface coatings is the primary technical method used to improve concrete durability. In this study, based on the plasma thermal spraying technology, a thermal-sprayed, ceramic-based coating was prepared on a concrete surface and evaluated using the drawing method, X-ray diffraction scanning electron microscopy with energy dispersive spectroscopy, X-ray computed tomography (X-CT), and frictional wear. Subsequently, performance tests were conducted. The test results showed that mullite powder was a suitable ceramic-based coating material. The coating had a good interfacial bonding ability with the concrete surface; moreover, the bonding site exhibited a chimeric state with an adhesion strength of 3.82 MPa. The wear rate of the coating material (0.02‰) is lower than that of the concrete matrix (0.06‰), resulting in improved surface wear resistance. SEM analysis reveals that the coating contains a considerable amount of amorphous or microcrystalline phases. The internal structure of the coating exhibits porous characteristics, with a total porosity of 10.35% and pore diameters predominantly ranging from 4 μm to 16 μm. At a distance of 80 μm from the coating site, the elements Al, O, and Si significantly contribute to the mullite components. The porous structures within the coating products are further verified using X-CT. This study offers a new possibility for ceramic coatings on hydraulic concrete.

Effect of Ti3SiC2 concentration on corrosion resistance and ICR in bipolar plates composite ceramic coatings

Ti3SiC2, a MAX-phase ceramic, amalgamates metallic and ceramic traits, delivering exceptional electrical conductivity and corrosion resistance. In this research, Ti3SiC2 composite coatings were applied to 316 L stainless steel via low-power atmospheric plasma spraying (APS), aiming to bolster the electrical and corrosion resistance attributes of bipolar plates (BPPs). A power input of 15 kW notably enhanced coating density, yielding a Ti3SiC2 concentration of 19.2 wt% in the coating. Extremes in the spraying power led to either diminished deposition efficiency or a reduction of Ti3SiC2 mass fraction below 5 wt%. Tafel curves demonstrated that specimens with elevated Ti3SiC2 mass fractions exhibited robust corrosion resistance, characterized by a self-corrosion potential of −162.5 mV and a self-corrosion current density of 1.7217 × 10−6 A·cm−2. Moreover, the interfacial contact resistance (ICR) between the coating and the gas diffusion layer was remarkably low (down to 5.49 mΩ·cm−2), indicating enhanced surface electron transfer with increasing Ti3SiC2 mass fractions.

Effect of Electrolyte Composition on the Structure and Tribological Properties of Ceramic Coatings Obtained by Micro-Arc Oxidation

Effect of Electrolyte Composition on the Structure and Tribological Properties of Ceramic Coatings Obtained by Micro-Arc Oxidation

Production of Porous ZrO2–TiO2 Ceramic Coatings on the Biomedical Ti-6Al-4V Alloy via AC PEO Treatment and Their Effects on the Corrosion Behavior in 0.9% NaCl

Production of Porous ZrO2–TiO2 Ceramic Coatings on the Biomedical Ti-6Al-4V Alloy via AC PEO Treatment and Their Effects on the Corrosion Behavior in 0.9% NaCl

Alumina-based ceramic coatings obtained by the SHS process for high temperature corrosion and wear protection of steel tubulars

Ceramic coatings have much potential for steel tubulars' protection against high temperature corrosion of gases and liquids, often containing abrasive solid particles, and to enhance their integrity in severe power generation, mineral and oil & gas production environments. Combining self-propagating high-temperature synthesis (SHS) with high-speed centrifugal process, alumina-based coatings were produced onto the inner surface of tubulars for these applications. According to the developed SHS batch formulation and the designed centrifugal device and process, well-consolidated composite ceramic layers with a thickness of 1.5–3 mm have been obtained. The developed SHS process does not create hazardous gases, and it takes ∼30 s for the ceramic phase formation. A high-level compaction due to centrifugal forces and a liquid phase sintering approach provided a dense gradient ceramic structure formed by oxide grains cemented by a glassy phase and bonded with a steel substrate through a thin iron layer. The coatings were successfully produced onto the inner surface of carbon and stainless steels’ tubes of up to 12 ft-lengths and standard dimensions from 2 to 3/8″ to 7.5” OD. The coatings were tested, for the first time, in wear and high-temperature corrosive environments, e.g., in steam–H2S–CO2 gases and molten salts, with encouraging results due to high contents of Al2O3 and some other oxides and consolidated ceramic structure. They can be recommended for applications in high-temperature (900 °C and greater) corrosive environments and erosive flows.

Effect of laser-assisted irradiation on plasma electrolytic oxidation of titanium alloys: Arc spot evolution characteristics and photoelectric synergistic mechanisms

Laser irradiation can be employed as an auxiliary energy field to optimize functional plasma electrolytic oxidation (PEO) coatings. Herein, the mechanism of the effect of laser-assisted irradiation on the morphology and composition of ceramic coatings prepared by PEO of titanium alloys in electrolytes with sodium tetraborate-based is discussed from the perspective of plasma arc spot evolution and photoelectric synergistic effect. X-ray diffraction (XRD), transmission electron microscopy (TEM), Mott-Schottky (M-S), scanning electron microscopy (SEM), and atomic force microscopy (AFM) were used to analyze the coating characteristics. The results showed that laser-assisted irradiation promoted the oxidation of the coatings, accelerated the conversion of the anatase phase to the rutile phase, reduced the oxygen vacancy defects and formed the "ant nest" porous microstructure. Monitoring of the voltage, electric field, and plasma discharge arc spot indicated that laser-assisted irradiation restricted the electric field diffusion on the anode surface, reduced the termination voltage, and significantly increased the intensity (maximum discharge percentage increased from 14.238 % to 20.358 %) and uniformity of distribution of the plasma discharge. Instantaneous photoresponse curves and electrochemical impedance spectroscopy confirmed that the PEO coatings exhibited fast and sustained photoelectric response under simultaneous laser irradiation, progressively enhanced with increasing laser irradiation energy. The photogenerated electrons excited by the semiconductor TiO2 coating under the simultaneous irradiation of laser can be used as the initial carriers of the electron avalanche, which induces the generation of a plasma on the surface of the anode and thus enhances the plasma discharge behavior, which is the fundamental reason for the optimization of the coating characteristics.

Microstructure, mechanical and electrochemical behavior of magnetron-sputtered carbothermic reduced iron-boride ceramic coatings

In this study, magnetron sputtered carbothermic reduced iron boride (FeB) coatings were developed on grey cast iron (GCI) substrates at different substrate temperatures. The impact of substrate temperature on structural, mechanical, and corrosion behavior was examined for two FeB deposition scenarios: FeB coatings deposited at room temperature (RT) and at 500 °C substrate temperature. The evolution of phases and microstructure was studied using XRD and FESEM, respectively. The mechanical properties, creep, deformation behavior, and adhesion strength (scratch test) of the deposited coatings were investigated using nanoindentation at ambient temperature. The highest hardness and Young’s modulus of 16 GPa and 231 GPa respectively, were achieved at 500 °C due to microstructural enhancement. Potentiodynamic polarization and electrochemical impedance spectroscopy were used to evaluate the corrosion behavior of the coatings. The results show that substrate temperature strongly influences the surface morphology of the coatings, which in turn governs the mechanical and corrosion behavior of the FeB coating. The FeB-coated GCI at 500 °C substrate temperature showed higher resistance to scratching, better mechanical properties, and improved corrosion resistance which is attributed to the enhanced adhesive strength, refined microstructure, and formation of protective oxide layers of FeB on the surface of the coatings.

Low Current Density Cathode Plasma Electrolytic Deposition of Aluminum Alloy Based on a Bipolar Pulse Power Supply

The present paper reported a novel bipolar-pulse cathodic plasma electrolytic deposition (BP-CPED) technique with a low current density. This newly developed CPED technique can break down the barriers of the existing CPED technique with higher current density. In this report, ceramic coatings were successfully prepared on aluminum alloy via the BP-CPED technique in an aqueous carbamide-based electrolyte. Data recording results in the reacting process show that there is the current density of the cathode below 0.15 A/cm2 and that of the anode below 0.035 A/cm2, which approximately reaches the level of conventional MAO technique. Interestingly, the addition of PEG into the electrolyte can further reduce the current density and effectively improve the coating quality. The kinetic of the BP-CPED process was discussed based on the evolution of current density/voltage-time curves and spark discharge phenomena. SEM observations illustrate that BP-CPED coatings possess a typical porous-surface feature. XRD analysis indicates that the coating was mainly composed of Al2O3 and Al4C3. Al2O3/Al4C3/ZrO2 composite coatings fabricated after Zr-doping reflected the successful Zr-incorporation into the coating, which demonstrated that the BP-CPED technique can be used to design the coating composition by the doping modification. The direct pull-off and thermal shock tests confirmed that new BP-CPED coatings obtained under the cathodic plasma discharge have excellent bonding strength. It is possible that this novel BP-CPED technique can provide a promising choice in developing the large-area CPED surface treatment for the industrial application.

The Role of Ceramic Materials in Surface Modification of Cutting Tools - A Review Paper

A modification cutting tool is a type of cutting tool that can be altered or adjusted to change its cutting properties. This can include changing the angle or shape of the cutting edge, adjusting the depth of cut, or modifying the material or coating used on the tool. These modifications allow for greater precision and efficiency in cutting operations, particularly in industries for manufacturing and construction different products. Ceramic materials can be used in coatings to provide a variety of benefits, such as corrosion, wear resistance , and thermal insulation. They also offer high hardness, low friction, and chemical stability. Ceramic coatings can be applied to various substrates including metals and ceramic. Modification of cutting tools using nanomaterial deposition is a promising approach to enhance their performance and durability. The process involves depositing one or more layer of nanosized particles onto the surface of the cutting tool, which can improve its mechanical, thermal, and tribological properties. Keywords: Ceramic materials ; coating ;cutting tools; coating process.