Ceramic Composite Coatings Research Articles

Abrasion resistance of polymer and polymer–ceramic composite coatings for steel hydraulic structures

There is an increased demand for abrasive wear-resistant coatings that add durability to steel hydraulic structures, particularly for those subjected to flowing water with debris and alternate wet/dry cycles. These coating systems provide not only corrosion and chemical resistance, but also good erosion and abrasion resistance to the metallic surfaces, which are constantly exposed to flowing water containing sand particles and debris. Generally, vinyl-based coatings are used on hydraulic steel structures to protect them from corrosion and abrasion. However, due to the existence of high water force and debris, the coating is abraded at a faster rate leading to significant maintenance and repair costs. In this study, abrasive wear resistance of conventional vinyl-based coating systems currently used on lock and dam steel structures by U.S. Army Corps of Engineers has been compared with polymer matrix composite coatings, fibrous polymer coatings, and ultrahigh molecular weight polyethylene (UHMWPE). Six coating systems were evaluated through two-body abrasion tests using a reciprocating abrader under dry and wet conditions. Furthermore, wettability of the coating systems and its effect on the wear rate under the presence of water was studied. In addition, scanning electron microscopy of the wear tracks on different coatings was conducted to study and identify their failure mechanisms. Based on the results, UHMWPE and polymer–ceramic composite coatings were found to perform significantly better than the conventional vinyl-based coatings.

High temperature microwave absorbing properties of plasma sprayed La0.6Sr0.4FeO3-δ/MgAl2O4 composite ceramic coatings

Microwave absorbing materials (MAM) which can be used in high temperature and oxidation environments are strongly demanded in application, for conventional MAM fail due to various factors at high temperature. In this work, ceramic coatings composed of La0.6Sr0.4FeO3-δ and MgAl2O4 have been successfully prepared via atmospheric plasma spraying and the microwave absorbing properties at high temperature are first reported. When the coatings of LSF/MAS matched with the metal substrate on thermal expansion, they can be treated repeatedly in the temperature range of 300 K–1173 K without peeling off. Meantime, the ceramic coatings with thickness of 1.5 mm showed considerable microwave absorption in the range of 8 GHz–18 GHz at high temperatures between 673 K–1173 K. The absorption bandwidth of LSF30 was 3.5 GHz for RL < −10 dB and 8 GHz for RL < −5 dB in the temperature range of 673 K–1173 K. LSF/MAS possesses the advantages of thin thickness and broad bandwidth at high temperatures, suggesting great potential as MAM in ultra-temperature environment.

Erosion and Wear Resistance of Cr3C2-NiCr Composite Ceramic Coating for Gun Barrel

A Cr3C2-NiCr coating was prepared on the PCrNi3MoVA steel via HVOF for the further use in gun barrel to reduce the wear and erosion of the PCrNi3MoVA steel. The microstructure and interfacial bonding state of the coating were analyzed by scanning electron microscopy (SEM). The erosion resistance of the coating was tested by high-speed hot airflow generated by a modified pressure-vented vessel. The high temperature friction coefficient and high temperature wear resistance of Cr3C2-NiCr coating and PCrNi3MoVA steel substrate were compared by high temperature friction and wear test. Results show that the Cr3C2-NiCr coating combines well with PCrNi3MoVA steel without cracking and shedding. The coating does not fall off under high-speed airflow erosion yet with an oxidation of the surface. The high temperature wear resistance of Cr3C2-NiCr coating is significantly better than that of PCrNi3MoVA steel substrate.

Research on the contact fatigue failure of thermal sprayed coating based on infrared thermography

ABSTRACTAiming to improve the accuracy of the contact life prediction of sprayed coatings, a series of contact fatigue tests are conducted on RM-1 tester. Five kinds of plasma sprayed Al2O3–40 wt%TiO2 composite ceramic coatings (AT40 ceramic coatings) of different quality and surface performance parameters are tested on the principle of central composite design. The passive infrared thermography is used to monitor the temperature change of the coating during the process of contact fatigue failure. The findings reveal that the infrared signal which is characteristic of non-stationary stochastic process shows a pre-warning against the failure of coatings. Both singularity detection and k-means clustering analysis come to a conclusion that the invalidating process of coating caused by contact fatigue is an interwoven result of crack initiation, crack propagation and crack instability fracture, etc. The nonstationarity of the infrared signal is further verified by non-parametric hypothesis test. Based on the results of correlation analysis between the contact point temperature range of the coating surface and the contact fatigue life, a reliable nonlinear prediction model is established.

Microstructure and friction coefficient of ceramic (TiC, TiN and B4C) reinforced Ni-based coating by laser cladding

Ni204 ceramic composite coatings with different mass fractions of TiC, TiN and B4C were successfully prepared on the surface of 45 steel by laser cladding. Microstructures of different ceramic coatings were studied using X-ray diffraction, scanning electron microscopy and laser confocal microscopy. The friction coefficient and microhardness of ceramic coatings were measured with a reciprocating friction wear machine and microhardness tester. The results show that ceramic coating has 766.8HV0.5 average microhardness and friction coefficient of 0.47 when 10%TiC, TiN, and B4C are added to initial powder Ni204. The microstructure of cladding layer is uniform and compact, and the microhardness and friction coefficient of the coating increased and decreased by factors 2.6 and 1.393 compared with initial powder. This is due to the presence of multiple phase ((Ti, Mo, Nb) (C, B, N)), carbide, nitride, (Ti, Mo, Nb) (C, B, N), and (Ti, Mo, Nb) (C, N) ring phase around TiC, TiN, and Ti(C, N) ceramic phases. Uniformly distributed reinforced phases in the coating inhibit extrusion by grinding balls on the surface of the ceramic coating, thus changing original abrasive wear mechanism, making wear marks more shallow, and decreasing friction coefficient of the surface.

Influences of Laser Remelting on Microstructure and Thermal Shock Resistance of Al2O3-13wt.%TiO2 Coatings Deposited by Plasma Spraying

Al2O3-13wt.%TiO2 composite ceramic coatings were prepared by plasma spraying and laser remelting. Morphology, microstructure and phase composition were analyzed by scanning electron microscope (SEM) and X-ray diffractometer (XRD). Meanwhile, effects of laser remelting on thermal shock resistance of plasma-sprayed coatings were investigated and the thermal shock failure mechanism of coatings were discussed. Results demonstrate that after laser remelting, particles on the ceramic coating are refined and the lamellar structure disappears, thus increasing density and getting a remelting coating basically without defects like cracks. Laser remelting metastable phase γ-Al2O3 is transformed into a stable phase α-Al2O3. Due to low heat conductivity coefficient of ceramic materials, it is impossible to remelt the whole ceramic coating at laser remelting. An isometric crystal remelted zone with small grains, a sintered zone and a lamellar remained plasma-sprayed zone are formed on the remelting ceramic coating. Compared with plasma-sprayed coating, the laser-remelted coating has better thermal shock resistance. The thermal shock failure form of ceramic coating deposited by plasma spraying is basically corner peeling, while the thermal shock failure forms of laser-remelted ceramic coating includes both corner peeling and considerable local peelings in the center. Influences of laser remelting on thermal shock resistance of coating are mainly manifested as reduced initial failure resistance of coatings, decelerated crack propagation on coatings and changing failure mode of coatings.

Research of the AK4-1 alloy microarc oxidation modes effect on the composite ceramic coatings erosion resistance

The article presents the results of the coatings erosion resistance experimental studies obtained by microarc oxidation using the AK4-1 aluminum alloy. The coatings formation modes by MAO varied in relation to the electrolytic components KOH, Na2SiO3 (gr/lconcentration); current density j (A/dm2) and the cathode/anode (Ic/Ia) currents ratio. The MAO coatings erosion resistance was determined from the ablation rate while the sample was blown with Al2O3 powder.

Oxidation Resistance and Microstructure Evaluation of a Polymer Derived Ceramic (PDC) Composite Coating Applied onto Sintered Steel.

Powder metallurgy is a competitive technology to produce ferrous near net shape parts for diverse engineering applications. However, their inherent porosity increases the susceptibility to oxidation and sealing their surface is mandatory to avoid premature degradation. Alongside, polymer derived ceramics (PDCs), such as silicon-carbonitride, have drawn attention concerning their high temperature and chemical stability. However, PDCs undergo volume shrinkage during ceramization that leads to defect formation. The shrinkage can be compensated by the addition of fillers, which are also capable of tailoring the ceramic resulting properties. This work evaluates the processing of PDC-based coatings loaded with ZrO2 and glass fillers to compensate for the shrinkage, densify the coating and seal the sintered steel surface. Therefore, polymeric slurries were sprayed onto sintered steel substrates, which were pyrolyzed at different temperatures for microstructural and oxidation resistance evaluation. Microstructural modifications caused by the enhanced glass viscous flow during pyrolysis at 800 °C resulted in more homogeneous, dense and protective coatings, which reduced the mass gain up to 40 wt% after 100 h of oxidation at 450 °C in air in comparison to the uncoated substrate. Moreover, no macrocracks or spallation were detected, confirming the feasibility of PDC composite barrier coatings for sintered steels.

CeO2 doped Al2O3 composite ceramic coatings fabricated on γ–TiAl alloys via cathodic plasma electrolytic deposition

CeO2 doped Al2O3 composite ceramic coatings were fabricated on TiAl alloys via cathodic plasma electrolytic deposition technique in 0.3 mol/L Al(NO3)3 ethanol electrolytes containing different concentrations of Ce(NO3)4. The effects of CeO2 doping contents on microstructures, elemental compositions, mechanical properties, high temperature oxidation resistance at 850 °C, and wear resistance against GCr15 balls at 200 °C of the coatings were investigated. The results indicated that the contents of CeO2 in composite coatings increased with increasing concentration of Ce(NO3)4, and composite coatings were composed of α–Al2O3 mainly, γ–Al2O3, and a little CeO2. The doping of CeO2 helped to improve the phase inversion from γ–Al2O3 to α–Al2O3. The crystallization and wear resistance of composite coatings increased due to the doping of CeO2. In the electrolyte containing 0.015 mol/L Ce(NO3)4, the coating was the most uniform and compact, and of the best high temperature oxidation resistance and mechanical properties.

A semi-empirical power-law model for the dip-coating of a substrate into a particle-containing, non-Newtonian, complex fluid system

The apparent viscosity of a particle suspension of ZrSi2 particles, polyhydromethylsiloxane (PHMS) preceramic polymer and n-Octane solvent, used to process polymer-derived ceramic composite coatings, is shown by viscometric experiments to be shear-thinning. The suspension is dip-coated onto substrates and the measured entrained coating thickness, h0, is observed to be a power-law function of U, the substrate extraction speed, as h0 = 0.5051U0.5. The experimentally observed semi-empirical model is directly compared to the results of a variety of theoretically derived Landau-Levich scaling laws and other models that have similar liquids and that include other effects. None of these cases predicts the scaling observed in these experiments. A correction factor is introduced to quantify the difference between the semi-empirical model with existing theoretical models. Possible explanations for the observed scaling behavior are presented.

Experimental study of the damage accumulation in composite materials and ceramic coatings by using of acoustic emission technique

Wide application of composite materials in reliable structures leads to the need for a detailed study of the processes of deformation, damage accumulation and fracture. Additional diagnostic methods for the experimental study of such processes in materials under the action of loads are used. Receiving and analyzing new experimental data will allow in the future to timely detect defects that indicate a decrease in the bearing capacity of the structure or may lead to the loss of its integrity. The aim of this work is to experimental study and describe the damage accumulation process in carbon-carbon composite material and to evaluate the performance of a functional ceramic coating by the using of the acoustic emission technique and digital images correlation method.

Microstructure and Corrosion Resistance of SiC Nanoparticles Reinforced Ceramic Composite Coating on Mg-Li Based Composite by Micro-Arc Oxidation

A SiC nanoparticles reinforced ceramic composite coating (SiCp/MAO) was successfully prepared on the YAl2 particles reinforced Mg-Li based composite using micro-arc oxidation. The phase composition and morphology of coatings were characterized by XRD, EDS, SEM and 3D laser scanning microscope. The corrosion behavior of coatings in a 3.5 wt% NaCl solution was evaluated by immersion test, potentiodynamic polarization and electrochemical impedance spectroscopy. With the increasing of SiC nanoparticles amount, the surface morphology of the composite coating was more compact and uniform with the reduction of pore diameter and micro-cracks. Meanwhile, the thickness and surface roughness of the composite coating were decreased. Both immersion and electrochemical tests showed that the 2g/L SiCp/MAO composite coating had the lowest corrosion rate, which proved that the addition of SiC nanoparticles improves the corrosion resistance of the composite coating.

A Dense Cr2O3/Al2O3 Composite Ceramic Coating Prepared by Electrodeposition and Sealing with Al2O3

A dense Cr2O3/Al2O3 composite coating was fabricated on 321L stainless steel by electrodepositing an Al2O3 layer on a Cr2O3 coating. The composition, structure, and properties of the obtained ceramic coating were investigated. The results showed that Al2O3 fully infiltrated the Cr2O3 coating and significantly improved the compactness of the ceramic coating by filling in the pores and cracks between the Cr2O3 grains. The composite ceramic coating was heat-treated at 750 °C and exhibited a high microhardness of 219.4 HV500g, a bonding strength of 46.5 MPa, and excellent anti-corrosion and deuterium permeation suppression properties.

Fracture behaviour of ceramic–metallic glass gradient transition coating

A new composite coating material of ceramic (Al2O3-40 wt% TiO2)–metallic glass (Fe56Cr23Mo13B8) gradient transition coating was successfully prepared by atmospheric plasma spraying technology, and a new theory of laminar–columnar structure gradient transition synergistic enhancement effect was proposed. The microstructure and element distribution of the composite coating were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), and electron probe microanalysis (EPMA). The fracture toughness and fracture behaviour of the composite coating were analysed via micro-hardness and three-point bending (3PB) tests. The results showed that the stress release of the ceramic–metallic glass gradient transition coating was stable compared with that of the conventional gradient coating in the stage of acute deformation, and the coating exhibited better fracture toughness. Different areas of the ceramic–metallic glass gradient transition coating exhibited different fracture behaviours. Additionally, the ceramic layer was made of columnar crystals, and the metal–glass layer was lamellar. The laminar–columnar structure gradient transition synergistic enhancement effect improved the anti-crack growth and fracture toughness. This study provides a new and viable option for the improvement of thermal spraying ceramic composite coatings.

High temperature tribology of polymer derived ceramic composite coatings

Polymer derived ceramic (PDC) composite coatings were deposited on AISI 304 substrates using siloxane based preceramic polymer polymethlysilsquioxane (PMS) and ZrSi2 as active filler or Ag as passive filler. The tribological performance of the composite coatings was evaluated at room temperature and moderately high temperatures (150 °C, 200 °C, 300 °C and 400 °C). The composite coatings showed low coefficient of friction (COF), µ, from 0.08 to 0.2 for SiOC-ZrSi2 composite coatings, and from 0.02 to 0.3 for SiOC-Ag composite coatings, at room temperature with increasing normal load from 1 to 5 N. High temperature tribology tests showed high COF values from 0.4 to 1 but low wear for SiOC-ZrSi2 coating, and low COF from 0.2 to 0.3 for SiOC-Ag coatings at lower temperature ranges. Low load friction tests at room temperature showed negligible wear in SiOC-ZrSi2 coatings, suggesting good wear resistant and lubricating properties due to formation of t-ZrO2 and carbon. Low COF and high amount of wear was observed in SiOC-Ag composite coatings at room temperature due to high ductility of Ag and smearing of wear debris in the wear track. The coatings and wear tracks were characterized to evaluate the lubrication and wear behavior.

Multi-Walled CNT Reinforcement to Thermal Spray Coatings

Thermal spraying coating techniques have emerged as very effective surface protection technology to apply protective coatings for corrosion and wear resistance applications. These coatings have gained more importance in recent past. Advances in powder and wire production have resulted in development of various types of surface coatings with excellent wear and corrosion resistance properties. Because of excellent mechanical, thermal and electrical properties of Carbon Nanotubes, CNTs reinforced composite coatings are being developed for various applications, e.g. automotive, aerospace and sports equipment industry. It is observed that if properly deposited, these CNTs ceramic composite coatings can provide improved properties like wear and corrosion resistance. It has been found that CNTs composite coatings can be successfully deposited by thermal spraying techniques, and these coatings provide better performance than conventional coatings. This paper reviews the performance of such coatings developed by various researchers.

Properties of thick ceramic composite coatings synthesized on an aluminium alloy by cathodic plasma electrolytic deposition

Cathodic plasma electrolytic deposition (CPED) was applied to efficiently produce a thick ceramic coating with superior wear and corrosion resistance on aluminium alloy. Ceramic composite coatings were synthesized in a glycerin-carbamide-based electrolyte with and without zirconium nitrate, and their phase components, morphologies and compositions were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and energy disperse spectroscopy (EDS). The tribological behaviour and electrochemical corrosion resistance were also evaluated. The results show that Al3C4-Al2O3 and Al3C4-Al2O3-ZrO2 coatings with thicknesses of 65 μm and 50 μm, respectively, were produced by DC-powered CPED in only 7 min. Relative to the uncoated alloy, both coated samples exhibited a much lower friction coefficient and wear rate. The ZrO2 incorporated in the coating enhanced the hardness of the coating and dramatically decreased the friction coefficient to 22% of that of the uncoated alloy. The incorporation of ZrO2 also increased the brittleness, resulting in a slightly higher wear rate than that of the ZrO2-free coating. The wear mechanisms of the Al3C4-Al2O3-ZrO2 and ZrO2-free coatings were concluded to be fatigue failure and abrasive wear, respectively. Both coated samples exhibited improved corrosion resistance. The ZrO2 introduced in the coating also decreased the corrosion current density to only 2.7% of that of the Al3C4-Al2O3 coating and enhanced the capacitive loop and impedance.

Improvement of tribological properties of as-sprayed 8YSZ coatings by in-situ synthesis C/MoS2 composite lubricant

Abstract The 8YSZ-C/MoS2 composite coating was fabricated to improve its tribological properties by introducing a novel and simple method. The C/MoS2 composite lubricants were synthesized in defects of 8YSZ coating via hydrothermal reaction connect with vacuum pressure impregnation. Results indicate that the porous C/MoS2 flower-like microsphere powders consist of interconnected ultrathin nanoflakes. The C and MoS2 are uniformly attached to the defects of 8YSZ coating and unable to assemble into microspheres due to the limitation of the size of pores and cracks. The tribological behaviors of the composite coating are significantly improved, which are devoted to the formation of the lubricating film. This preparation technique provides a novel approach to establish self-lubricating ceramic composite coatings with temperature-sensitive solid lubricants.

Microstructure and properties of Al2O3-Y2O3 ceramic composite coatings fabricated by plasma spraying

The Al2O3-Y2O3 system composite coatings were prepared by plasma spraying Al2O3-Y2O3 composite powders with or without TiO2 addition. The effects of TiO2 on the microstructure and properties of the Al2O3-Y2O3 coatings were investigated. The results show that the composition of the composite powders had great influence on their microstructure evolution. The Al2O3-Y2O3 coatings were composed mainly of α-Al2O3 and c-Y2O3. There were amorphous phase, Y3Al5O12 (YAG) phase and Y4Al2O9 (YAM) phase formed in the Al2O3-Y2O3 coating. The content of Y3Al5O12 in the Al2O3-Y2O3-TiO2 coating increased with addition of 2 wt% TiO2, and the content of Y4Al2O9 and amorphous phases decreased correspondingly. There was no Y3Al5O12 formed in the Al2O3-Y2O3-TiO2 coatings with further increasing of TiO2, while the content of amorphous phase increased. The microhardness of the Al2O3-Y2O3-TiO2 coating was improved with the addition of 2 wt% TiO2, which was attributed to its lower porosity, more uniform microstructure, more YAG phase, and less amorphous phase. The microhardness of the Al2O3-Y2O3-TiO2 coatings decreased significantly with further increasing of TiO2 due to the significant decrease of YAG phase and the increase of the amorphous phase. The Al2O3-Y2O3-TiO2 coating with addition of 2 wt% TiO2 possessed higher toughness, adhesive strength and wear resistance compared with the Al2O3-Y2O3 coating, which was due to its lower porosity, smaller and spherical pores, and more YAG phase.

Improvement of friction units of power plants by aplying ceramic composite spray coatings

Modifying the working surface of a product by applying protective and functional coatings makes possible considerable changes in the mechanical, optical, electrical, magnetic, thermal and chemical properties of the original structural material, its real surface, producing articles with protective, for example, anti-corrosion, wear-resistant and other properties. We investigated the possibility of improving the friction units of aircraft power plants by applying nanostructured ceramic composite spray coatings. A heavily loaded bearing forming a part of the gearbox of a turbojet engine is used as a prototype of the friction unit. The advantages and drawbacks of improved friction units as compared to production models and their prototypes made according to an improved technology are assessed. The results obtained during the experimental work are presented. A positive conclusion is made about the use of nanostructured composite materials in the development of friction units; the most favorable method of coating is determined.