Mechanical Properties Of Ceramic Coatings Research Articles

изико-механические свойства керамических покрытий, получаемых короткоимпульсной лазерной наплавкой порошковой смеси на основе бора

Modern repair production that implements traditional technologies for making restorative coatings has lost its relevance, since it cannot provide the necessary physical and mechanical properties of the coatings. The problem is that in modern metallurgy there is no line of repair additive materials with high strength and technological properties. Therefore, the issues of searching for innovative materials and technologies for their application on the surface of worn parts are relevant and require fundamental research. The aim of the work is to study the physical and mechanical properties of ceramic coatings obtained by short-pulse laser treatment. To achieve this goal, ceramic compositions based on boron carbide, additionally doped with boron nitride (0 to 40% BN), magnesium oxide (2 to 10% MgO) and lithium (5 to 25% LiO), were used. The scientifi c novelty of the research lies in the application of selective laser sintering technologies in the formation of thin coatings (up to 200 μm) under conditions of a short-pulse laser refl ow of powder media. To assess the physical and mechanical properties, laboratory research methods were used, in particular, analysis of the microhardness of the created restorative coatings, microstructure and tribological performance indicators using modern techniques and instrumentation. The research results confi rm the possibility of practical implementation of restorative coatings based on ceramic compounds. The multi-layer ceramic coatings (B4C-BN- MgO-Li2O) up to 200 μm thick showed good workability, low coeffi cient of friction (0.18) and the ability to work under high dynamic loads in the absence of intensive lubrication. The structure of the coatings has a dense adhesive zone with no visible defects. The presented results of studying the physic-mechanical properties of ceramic coatings have high research credentials and practical signifi cance, and their application will improve the durability of machine parts in the conditions of their operation.

Effects of Benzotriazole on nano-mechanical properties of zirconia–alumina–Benzotriazole nanocomposite coating deposited on Al 2024 by the sol–gel method

The concentration of Benzotriazole plays an important role in the mechanical properties of ceramic coatings. In this work, hybrid nano-composite zirconia–alumina–Benzotriazole coatings with 1.2, 2.4, 3.6 and 4.8% of Benzotriazole are deposited on the Al 2024 substrate by the sol–gel technique. The phase, structure, and morphology are determined by grazing-incidence X-ray diffraction, Fourier-transform infrared spectroscopy, and field-emission scanning electron microscopy and the nano-mechanical properties are assessed by atomic force microscopy at loads of 50 and 60 µN. Uniform and homogenous amorphous coatings are deposited at 150 °C and the thicknesses of the zirconia–alumina and zirconia–alumina–Benzotriazole coatings with 1.2%, 2.4%, 3.6%, and 4.8% Benzotriazole are 670, 560, 750, 790, and 1040 nm, respectively. The surface roughness of the coatings decreases by 3.5 and 8 times after introducing 1.2% and 3.6% Benzotriazole to the coatings, respectively, but further increasing the Benzotriazole concentration from 3.6 to 4.8% decreases the hardness, strength, and maximum shear tension. The optimal concentration of Benzotriazole depends on the Hertzian pressure and the hardness and strength of the zirconia–alumina–3.6% Benzotriazole under a load of 60 µN are 23 and 46 times higher than those of the zirconia–alumina coating. The smallest friction coefficient of 0.11 is observed at a load of 60 µN and abrasive wear and shear are dominant.

Microstructure and mechanical properties of ceramic coatings formed on 6063 aluminium alloy by micro-arc oxidation

The microstructure and mechanical properties of ceramic coatings formed on 6063 aluminium alloy obtained in silicate-, borate- and aluminate-based electrolyte without and with nanoadditive Al2O3 and TiO2 by micro-arc oxidation (MAO) were studied by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), microhardness and friction–abrasion tests, respectively. SEM results show that coatings with nanoadditive have less porosities than those without nanoadditive. XRD results reveal that nanoadditive-containing coatings contain more oxides compared with nanoadditive-free coatings in all cases, which are consistent with the EDS analysis. Mechanical properties tests show that nanoadditive Al2O3-containing coatings have higher microhardness values compared with the other coatings obtained in silicate-, borate- and aluminate-based electrolyte. On the other hand, nanoadditive has a positive effect on improving the wearing-resistance of MAO coatings in all cases. Furthermore, the borate-MAO coatings present an inferior anti-wearing property compared with the silicate- and aluminate-MAO coatings for both the nanoadditive-free and nanoadditive-containing coatings.

Corrosion and Multi-Scale Mechanical Behaviour of Plasma Electrolytic Oxidation (PEO) and Hard Anodized (HA) Coatings on AA 2219 Aluminum Alloy

The electrochemical corrosion and mechanical properties of ceramic coatings fabricated by plasma electrolytic coating (PEO) and hard anodizing (HA) methods comparatively examined for AA2219. Potentiodynamic polarization results revealed that the corrosion resistance of both coatings are comparable to each other. However, the indentation and scratch testing indicated that the hardness and modulus of the PEO coating was significantly higher when compared to HA coating. The critical load (Lc2) causing adhesive failure of the PEO coating was much high (19N) when compared to HA coating (10N) showing better adhesive strength of the PEO coating.Key words: Plasma electrolytic oxidation (PEO), potentiodynamic polarization, nanoindentation, hard anodizing

Microstructures and mechanical properties of duplex-treated composite ceramic coatings with and without compound layer

Duplex-treated composite ceramic coatings with and without compound layer were produced by the combination of plasma nitrocarburizing and follow-up multi-arc ion plating. The microstructures and mechanical properties of the ceramic coatings were investigated by means of X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy, in association with property characterization. The results show that the composite ceramic coatings are composed of an inner nitrocarburized layer, a CrN interlayer and an outmost AlCrTiSiN layer. The AlCrTiSiN layer consists mainly of alternately nanoscaled (Cr,Al)N sublayer and amorphous sublayer with a few (Ti,Al)N phases embedded in a matrix of amorphous Si3N4 and Si. The compound layer has transformed to the γ′-phase sublayer, which enhances considerably the adhesion strength of the CrN interlayer to compound layer. The improved adhesion strength is attributed to the γ′-phase acting as nucleation sites of epitaxial growth for the CrN phase. The composite ceramic coating with compound layer reveals much higher hardness, bearing capacity and wear resistance when compared with the composite ceramic coating without compound layer. The improvement of mechanical and tribological properties is associated with presence of the γ′-phase sublayer, which provides a smooth transition, gradient in hardness and stress between the substrate and the CrN/AlCrTiSiN coating. In addition, the hard γ′-phase sublayer provides a strong supporting effect for CrN/AlCrTiSiN layer under loading.

Infrared Optical and Mechanical Properties of Ceramic Coatings Fabricated by Aerosol Deposition

The possibility and mechanical improvement of the infrared ceramic coatings fabricated on fluoride substrates at room temperature by aerosol deposition (AD) were investigated aiming to optical components for infrared applications and devices. The yttria coating possibility fabricated on barium fluoride substrates by the AD process was found by adjusting one of the deposition conditions. The optical and mechanical properties of the fabricated ceramic coatings, which are important in practical applications, were evaluated by transmittance and hardness measurements respectively. The mechanical hardness of the fabricated yttria single coatings was increased to 4 times higher than that of the barium fluoride substrates. Furthermore, by an additional layer on a barium fluoride substrate, the mechanical properties of the fabricated multi-coatings including an upper yttria layer were improved from that of the single yttria coating on the barium fluoride substrate, retaining the IR transmittance of the single yttria coating at the wavelength of 10μm.

Evaluating Adhesion of Ceramic Coatings by Scratch Testing

Adhesion is one of the most important mechanical properties of ceramic coatings. Scratch testing is considered as a simple and effective method to evaluate adhesion of ceramic coatings. In this paper, the critical normal forces and scratch morphologies for different coating-substrate systems were studied by scratch testing. It is shown that the critical normal force obtained by acoustic emission (AE) signals decreases from 12 N to 7 N when the applied normal force rate increases from 20 N/min to 100 N/min for CVD SiC on C, and the failure area of this scratched sample increases with increasing maximum normal force; Based on scratch morphologies, spallation or delamination can be observed for hard-brittle coatings on glass or metal, while discontinuous or continuous ductile perforation can be observed for ductile coatings on metal; The critical normal force for hard-brittle coatings can be effectively obtained by AE signals.

Structure and Mechanical Properties of Ceramic Coatings Fabricated by Micro-Arc Oxidation

Al2O3 ceramic coatings were directly prepared on 6063 aluminum alloy in borate electrolytes by micro-arc oxidation (MAO) technique. The phase composition, microstructure, elemental distribution, and micro-hardness of Al2O3 ceramic coatings were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and micro-hardness test. XRD results show that the coating consists of α-Al2O3 and γ-Al2O3. SEM results show that the pores with different sizes distributed all over the coating surface. Adhesion and tribological and wear tests were also performed. It was found that ceramic coatings with high hardness, excellent adhesion and wear resistance could be formed.

Structure and mechanical properties of ceramic coatings fabricated by plasma electrolytic oxidation on aluminized steel

Ceramic coatings were formed by plasma electrolytic oxidation (PEO) on aluminized steel. Characteristics of the average anodic voltages versus treatment time were observed during the PEO process. The micrographs, compositions and mechanical properties of ceramic coatings were investigated. The results show that the anodic voltage profile for processing of aluminized steel is similar to that for processing bulk Al alloy during early PEO stages and that the thickness of ceramic coating increases approximately linearly with the Al layer consumption. Once the Al layer is completely transformed, the FeAl intermetallic layer begins to participate in the PEO process. At this point, the anodic voltage of aluminized steel descends, and the thickness of ceramic coating grows more slowly. At the same time, some micro-cracks are observed at the Al 2O 3/FeAl interface. The final ceramic coating mainly consists of γ-Al 2O 3, mullite, and α-Al 2O 3 phases. PEO ceramic coatings have excellent elastic recovery and high load supporting performance. Nanohardness of ceramic coating reaches about 19.6 GPa.

308 セラミックス溶射皮膜の機械的特性と溶射中基材温度の関係(OS2-2 皮膜・薄膜の機械的特性,OS2 薄膜・皮膜とその膜構造の特性評価)

308 セラミックス溶射皮膜の機械的特性と溶射中基材温度の関係(OS2-2 皮膜・薄膜の機械的特性,OS2 薄膜・皮膜とその膜構造の特性評価)

Microstructure and mechanical properties of ceramic coatings on Ti and Ti-based alloy

Results of a study of silica and silica–titania sol–gel coatings for the creation of intermediate interfaces between commercially pure Ti or titanium alloy Ti6Al4VELI and dental porcelain are presented. Coatings of SiO2 on Ti6Al4V alloy and SiO2–TiO2 on Ti were deposited using sol–gel method. Surface microstructures and wear behaviour of the coatings were studied by using scanning electron microscopy with electron diffraction spectroscopy and pin-on-disc method. It is found that (1) Ti6Al4V/SiO2 and Ti/SiO2–TiO2 coatings obtained by the sol–gel method are compact, chemically homogeneous and relatively rough, and (2) the smaller wear of SiO2 coatings than that of SiO2–TiO2 coatings is associated with differences in their microstructure and roughness.

Evaluation of mechanical properties of ceramic coatings on a metal substrate

Nanoindentation and tensile tests were performed for TiN coatings on a stainless steel substrate to investigate the indentation induced deformation behavior of the coatings and the adhesion of the coating–substrate interface. Load–displacement curves show the transition of plastic deformation state from coating only to coating–substrate composite in a penetration depth of 1/10 of the coating thickness, which is approximately two times smaller than that of metal coatings. We employed two specimens with different interface characteristics for the evaluation of the adhesion. The tensile test can clearly detect the difference by the analysis of statistics of extremes for the maximum crack spacing, while the indentation results show no difference, suggesting that the tensile test is superior in detecting the adhesion of the coating–substrate interface.

Properties of protective oxide scales containing cerium on Incoloy 800H in oxidizing and sulfidizing environments. I. Constant-extension-rate study of mechanical properties

The mechanical properties of ceramic coatings containing cerium oxide, prepared by the sol-gel method and used to protect Incoloy 800H against aggressive environments, are reported. Deformation and cracking behavior in oxidizing and sulfidizing environments has been investigated by constant-extension-rate tests. Extension rates were between 9.3×10−6 and 3.7×10−7 sec−1 at 823 <T<973 K. Under these conditions, cerium oxide sol-gel-coated specimens do not show any failure at extensions of 1.0% or more, but in hydrogen, sulfide failure is found at lower extensions than in air.

Interlamellar contact within plasma-sprayed coatings

Transmission electron microscopy of plasma-sprayed Al 2O 3 coatings shows that the interfaces between lamellae consist of regions of perfect contact and regions in which there are gaps of 0.01–0.1 μm which probably arise from adsorbed or entrapped gas between impinging droplets and previously solidified material. This structure is consistent with a previously suggested model for coating formation and can explain some of the mechanical properties of ceramic coatings.