Properties Of Different Coatings Research Articles

Lubricant savings in sheet metal forming through thermally oxidized wear protection layers

Increasing demands on quality, variety of shapes and complexity of deep-drawn components with simultaneous price stability make the development of innovative solutions in the field of deep-drawing indispensable. For ecological and economic reasons, there is a great interest in reducing the amount of lubricant required in forming processes to a minimum. In this work, tool coatings for forming tools are to be investigated and further developed in order to use their friction-reducing properties on the tribo-system and thus enable a reduction in the use of lubricants. For this purpose, in this research strip drawing tests are carried out to investigate the friction-influencing properties of different coatings and their potential for lubricant saving. Therefore, cylindrical forming heads are provided with different coating systems. Strips of aluminum sheet are drawn around the forming heads at an angle of 90°. The amount of lubricant applied is varied. Friction values are recorded and analyzed for each system. Wear mechanisms are identified, examined and evaluated macroscopically and microscopically. For this purpose, energy dispersive X-ray spectroscope (EDX) and scanning electron microscope (SEM) examinations are carried out. A statement on the potential of the investigated coatings for lubricant saving is derived from the results.

Investigation on the tribological properties of different coatings of cutting tool with reciprocating friction test

Investigation on the tribological properties of different coatings of cutting tool with reciprocating friction test

A solar-driven adsorbent based on Al-fumarate metal-organic framework coating with high water cycle efficiency

Adsorption bed using pelleted metal-organic frameworks (MOFs) shows high water adsorption capacity, but have low adsorption/desorption rate, which limits the water cycling efficiency. And coating MOFs on the thermal-conductive surface can enhance the water adsorption/desorption rate by promoting heat transfer, furthermore, they can be efficiently driven by green solar light. Based on it, in this work, a novel mixed-solvothermal in-situ synthesis technology of Al-fumarate MOF coating on aluminum foil was developed. The results showed that by respectively adjusting the DMF/H2O ratios, fumaric acid molar contents, and the crystallization temperatures from 5/30–30/5, 2–10 mmol, and 90–120 °C, Al-fumarate MOF with uniform dispersion and controllable thickness (50–620 μm) on aluminum foil could be synthesized directly. The water release properties of different coatings under 1 and 1.2 sunlight (1 kW/m2 and 1.2 kW/m2) were tested. The results showed that the coating with different thicknesses can achieve complete desorption within 8–20 min at a sunlight intensity of 1.2 kW/m2, and the water yield through one cycle can reach 157 g/m2. The coating which displayed a thin strip cauliflower crystal morphology possessed a high adsorption capacity, fast adsorption/desorption rate, low desorption temperature as well as excellent cycle stability.

Protective Coatings for Metals in Scientific—Technical Heritage: The Collection of the Spanish National Museum of Science and Technology (MUNCYT)

This paper presents results on the protective properties of different coatings over metals representative of those found in scientific–technical heritage collections. An examination of several objects in the collection of the Spanish National Museum of Science and Technology have allowed the identification of brass and steel as the most representative metals, and the existence of coatings (mainly shellac and acrylic resins) applied for aesthetic and/or conservation purposes. Based on these findings, brass and steel coupons coated with Paraloid B-44, B-48, B-67, B-72, Incralac, Cosmolloid H80, B-72 + H80 double layer and shellac have been studied to carry out a first screening in order to select the most promising candidates and determine the most appropriate methodology and key factors for the study. Coatings have been aged up to 336 h using cycles of UV light and water condensation. The change in the aspect of the coupons has been assessed via visual examination, optical microscopy and colorimetric measurements, with B-44 and Incralac showing the least change. EIS has been used for a quantitative evaluation of the protective properties and FTIR to measure chemical changes experienced by some coatings, such as B-48 and B-67. These evaluations allowed us to follow, understand and compare the behaviour of the different coatings and substrates after artificial ageing.

Geopolymer coating modified with reduced graphene oxide for improving steel corrosion resistance

Among the different existing techniques, the surface coating on steel provides an economical means to address the corrosion issue. In this study, a geopolymer anti-corrosion coating modified with in-situ reduced graphene oxide (RGO) was developed, and its physicochemical and electrochemical properties were investigated. Four different graphene oxide (GO) contents (i.e., 0.05%, 0.1%, 0.5% and 1% of the binder by weight) were studied. The GO content in the coating was optimized based on its corrosion protection ability, and the performance of GO modified geopolymer coated steel was compared to that of bare steel, cement coated steel and blank geopolymer coated steel when immersed in a 3.5% NaCl solution. It was observed that using a GO content of 0.1% can increase the corrosion resistance of geopolymer-coated steel by more than two orders of magnitude compared to bare carbon steel. Additionally, the physiochemical properties of different coatings were investigated, and the corrosion protection mechanism with RGO modification has been further elaborated.

Evaluation of mechanical properties of YSZ TBCs doped by different ratios of Eu3+ ions after isothermal oxidation

Thermal barrier coatings (TBCs) are essential to improve the thermal insulation performance of high-temperature components. Rare earth element (Eu3+) doped yttrium stabilized zirconia (YSZ) TBCs have been proved to be an ideal solution for non-destructive testing of internal damages. Based on this theory, two types of coatings deposited by air plasma spray (APS) on Hastelloy-X were investigated: (1) Eu3+ doped YSZ (dopant ratios 1 mol%, 2 mol%, 4 mol%, respectively), (2) traditional undoped 8YSZ. Isothermal oxidation treatment at 1100 °C, in increments of 10h until the failure of the coatings are conducted to evaluate the mechanical properties of different coatings. The microscopic morphology and phase of the coatings were analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD) patterns, respectively. The indentation testing methods were used to study the apparent interfacial fracture toughness and the hardness of the ceramic top coat. Results show that the Vickers hardness of the top coat increases with the decrease of porosity in the early stage and then decreases with the heat treatment time increasing in the long-term stage. Simultaneously, compared with the undoped 8YSZ coating, the fracture toughness increased with the dopant of Eu3+ ions increasing, from 1 mol% to 2 mol%, nevertheless, that of 4 mol% Eu3+ doped YSZ decreased compared with in the undoped 8 YSZ. For all types of specimens, the interfacial fracture toughness decreases with the increase of isothermal oxidation time. Results also indicate that the content of Eu3+ doping does not affect the microstructure and interfacial morphology of the YSZ coating as well as the growth law of thermally grown oxides (TGO). Furthermore, EDS detection found that the Eu3+ ions almost do not diffuse inside the TBCs system after isothermal oxidation treatment.

One zirconia-based ceramic coating strategy of combustion stabilization for fuel-rich flames in a small-scale burner

From the perspective of the thermal/chemical performance management of a slot burner, three kinds of blended coatings with the low thermal conductivity and certain chemical activities, including 30wt.%Y2O3/ZrO2, 30wt.%MgO/ZrO2 and 30wt.%Al2O3/ZrO2, were prepared on stainless steel walls plated by atmospheric plasma spraying. The effects of coating material, wall temperature, and equivalence ratio on fuel-rich methane flame characteristics were investigated experimentally. The OH planar laser-induced fluorescence (OH-PLIF) technique was used to obtain OH intensity and flame anchoring location. The physical and chemical properties of different coatings before and after spraying were analyzed by a series of material and surface characterization techniques. Results show that compared with pure ZrO2 coating, the quenching distances of three ZrO2-based blended coatings with Y2O3, MgO, and Al2O3 decrease to some extent, resulting in the minimum quenching distance of Al2O3/ZrO2 coating, and the maximum one for Y2O3/ZrO2 coating. Meanwhile, the blended coating walls result in the higher flame anchoring location than that of pure ZrO2 in most cases, in which the coating of Y2O3/ZrO2 displays the highest location. The blended coatings have higher thermal conductivity, which is beneficial to balance part of the heat loss through the axial heat recirculation of wall structures, and thus expanding stability limits at low temperatures. In addition, partial lattice solid solutions are formed in mixture systems after the ultra-high-temperature thermal spraying, leading to more surface lattice oxygen and stronger chemical promotion. In summary, reasonable allocation of ZrO2-based ceramic components as coating wall is an effective alternative strategy to control flame stabilization in small-scale combustion devices.

Effect of Ni-coated WC reinforced particles on microstructure and mechanical properties of laser cladding Fe-Co duplex coating

Fe-Co duplex coating has been deposited onto crystallizer copper plates surface by Nd: YAG laser cladding. To further improve the wear resistance of the duplex coating, the effects of various nickel-coated WC (Ni/WC) contents on the microstructural characterization and wear properties of different coatings have been investigated by using optical microscopy (OM), X-ray diffractometer (XRD), scanning electron microscope (SEM) and energy disperse spectroscope (EDS). The experimental results indicated that the microstructures of the Co-based layer were mainly composed of dendrite and eutectic structure, which were refined with increasing Ni/WC content. Compared with the Co-based layer without Ni/WC, the addition of Ni/WC facilitated the formation of new phase Co3W9C4 and WC. Moreover, the decomposition of WC particles on the Co-based layer enhanced the effect of solid solution strengthening, resulting in an improvement of the microhardness and wear resistance of the working layer. Based on the obtained results, the incorporation of Ni/WC was an attainable way to improve the tribological properties of Co-based alloy coatings.

Wear properties and microstructural analyses of Fe-based coatings with various WC contents on H13 die steel by laser cladding

Microhardness, wear properties and microstructure of Fe-based coatings with various WC contents on H13 hot-working die steel by laser cladding were investigated. Special attention was paid to the effects of various WC contents on the microstructural characterization and wear properties of different coatings by means of optical microscopy (OM) and scanning electron microscopy (SEM). Results indicated that only a small part of the periphery of the WC in the WC-added coatings was melted, and the un-melted WC particles in the coatings acted as a hard reinforcement. Besides, the microhardness in the cladding layer increased with the increment of the mass fraction of WC particles, and presented a gradient distribution along in-depth direction of the coatings. Furthermore, the Fe-based clad coating with WC particles exhibited a higher wear resistance and a lower friction coefficient compared with the substrate and Fe-based clad coating. In addition, the influence mechanism of WC particles on microstructural evolution and wear resistance was also discussed.

Tribological effects of mold surface coatings during ejection in micro injection molding

The effects of different mold coatings on the ejection force in micro injection molding were experimentally investigated. Two diamond-like-carbon and chromium titanium niobium nitride coatings were selected in accordance with their potential affinity with the considered injected polymers. The obtained results were correlated with the wetting properties for all the combinations of injected polymers and surface coatings. Moreover, the tribological properties of the different coatings were evaluated using an off-line friction test. The ejection force peak was correlated to the static friction coefficient. For each polymer a good linear correlation between the online and the offline friction characterization was identified, indicating the effectiveness of the proposed procedure in evaluating the tribological properties of different coatings for different polymers.

PH-Responsive Nanostructured Polyaniline Capsules for Self-Healing Corrosion Protection: The Influence of Capsule Concentration

Nanostructured hollow polyaniline (PANI) capsules are good candidates for encapsulation of corrosion inhibitors and pH-responsive release when incorporated into organic coatings. In previous work the corrosion protection performance of PANI capsules containing organic inhibitor 2-Mercaptobenzothiazole (MBT) was demonstrated. The present work studies the influence of capsule concentrations (i.e. 0.3, 1 and 2 wt.%) on the corrosion protection properties of the coating system. Anti-corrosion properties of different coatings were compared by means of Electrochemical Impedance Spectroscopy (EIS), and Scanning Vibrating Electrode Technique (SVET). MBT loaded PANI capsules in epoxy ester coating on AA2024-T3 substrate allows for a self-healing effect to be obtained during the corrosion process. The results showed that the concentration of MBT loaded PANI capsules greatly influence the corrosion protection properties of the coatings, and the best corrosion protection performance was observed for the coating system containing 1 wt% PANI capsules. The impedance value of the scratched area of this coating after 7 days of immersion was one order of magnitude higher than that of the control sample.

Effect of Multilayer Nanocomposite TiAlSiN/TiSiN/TiAlN Coating on Wear Behavior of Carbide Tools in the Milling of Hardened AISI D2 Steel

Thin hard coatings are widely used in the protection of cutting tools, dies and molds to prolong their wear resistance and lifetime. Superior properties of different coatings can be combined with multilayer design, and especially a higher microhardness can be obtained by nanocomposite structures. In this study, a multilayer design composing of TiAlSiN, TiSiN and TiAlN layers was applied on carbide cutting tools. The top TiAlSiN layer has a nanocomposite structure of crystalline fcc-TiAlN and amorphous Si3N4 phases. The multilayer nanocomposite TiAlSiN/TiSiN/TiAlN coating was deposited on the carbide cutting tool using an industrial magnetron sputtering system. Wear behavior of the coated tools was investigated in the milling of hardened AISI D2 steel (~55 HRc). The changes in tool wear and surface roughness as a function of cutting distance were recorded. Wear mechanisms and types were investigated using optical and scanning electron microscopy in combination with energy dispersive spectroscopy. It was found that the multilayer nanocomposite TiAlSiN/TiSiN/TiAlN coating provides at least 1.2 times higher wear resistance and a longer lifetime than single layer TiN and TiAlN coatings. Main wear mechanisms are abrasion and adhesion of the workpiece material on the cutting edge. As a result, wear types are notch wear and build-up-edge formation.

Evaluation of icephobic coatings—Screening of different coatings and influence of roughness

Icing of wind turbines affects energy production, causes mechanical failures and increases safety hazards in general; hence there is an enormous demand for powerful anti-icing methods. To investigate the icephobic properties of different coatings, ice adhesion measurements were performed with a 0° cone test to determine ice adhesion strengths between coating and ice. Various coatings with different icephobic properties were investigated, e.g., hydrophilic and hydrophobic coatings, sol–gel based coatings containing fluorinated compounds and viscoelastic rubbers, as well as commercially available icephobic products. The coatings currently used on wind turbines showed an adhesion to ice that is comparable to that of bare aluminium; meaning a quite high adhesion to ice. Very low adhesion values were obtained in the case of coatings consisting of viscoelastic elastomers. Additionally, the influence of surface roughness on ice adhesion has been examined. Aluminium pins were chemically and mechanically roughened and their ice adhesion was determined. These pins were further coated with a fluorine-containing coating in order to study the influence of minimized surface energies. Shear stress of those coated pins was considerably reduced, however, rough surfaces showed higher ice adhesion than smooth ones.

Sol–gel processing of hybrid nanocomposite protective coatings using experimental design

Environmentally friendly hybrid nanocomposite sol–gel coatings as substitutes for chromate conversion coatings have attracted a great deal of attention recently. The coatings derived from hydrolysis and condensation of polymerizable silane precursors tetraethylorthosilicate (TEOS) and 3-glycidoxypropyltrimethoxysilane (GPTMS) were deposited onAA5083 substrates by a dip coating technique. Statistical design of experimental (DoE) methodology based on Taguchi orthogonal design has been used to study and optimize compositional and process parameters using multifactor analysis of variance (ANOVA) analysis method and the adhesion strength of coatings to the substrate as per pull off test has been used as a response. Adhesive strength of sol–gel coatings to the substrate was evaluated using pull off and tape tests. Bending, impact resistance and pencil scratch tests were employed to characterize mechanical properties of different coatings. The surface morphology and chemical composition of the hybrid films were studied by atomic force microscopy (AFM) and Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR/FTIR), respectively. Optical microscopy (OM) and field emission scanning electron microscopy (FE-SEM) were used to investigate structure of the coatings. The results show an increase of the hydrolysis water content at a constant organic/inorganic molar ratio and other variable parameters increases adhesion of coatings to substrate, and optimum coatings exhibit excellent mechanical properties as well as adhesive to the substrate.

Design of Anti-Icing Coatings Using Supercooled Droplets As Nano-to-Microscale Probes

A multiscale simulation-based approach is presented for predicting anti-icing properties of nanocomposite coatings. Development of robust anti-icing coatings is a challenging task. An anti-icing coating that can prevent in-flight icing is of particular interest to the aircraft industry. A multiscale simulations based approach is developed to provide insights into the complex effect of coating material and surface topology on the prevention of in-flight icing. Chemical properties of different coatings and kinetics of icing or inhibition of ice nucleation are calculated from nanoscale atomistic simulations. In addition, in-flight icing environments including impingement and rolling of supercooled microdroplet and nucleation of ice under wind shear have been implemented using fluid dynamics methodologies. A model for icing in nano-to-microscale for surfaces with known chemical composition and surface topology is used for developing predictive capabilities regarding anti-icing performance of potential coatings. In this work, fluorinated polyhedral oligomericsilsesquioxanes molecules have been used to increase nanoscale roughness when embedded in a polycarbonate polymeric matrix. The findings suggest that a successful anti-icing coating will require precise control over nanoscale and microscale roughness. The multiscale methodology presented therefore can potentially help in identifying coupled effects of material, surface topology, and icing environment for promising coatings before performing icing tunnel experiments.

Evaluación de la oxidación superficial de recubrimientos de Ti6Al4V obtenidos por recubrimiento por láser

It has been studied the influence of processing parameters on the superficial oxidation and mechanical properties of different coatings of Ti6Al4V. The high chemical reactivity of titanium powder, and the high temperature reached during laser processing, produces a great variety of colors in the oxides formed. This oxidation can have a detrimental effect on the behavior in service so that its evaluation is essential. Although the influence of processing on the color of the oxides formed is clear, there is no simple relationship to explain its mechanical properties. For this reason it has been applied a methodology based on microscopy, microanalysis wavelength spectroscopy (WDS) and nanoindentation. The results indicate no significant differences in hardness and elastic modulus between two coatings with different colors of oxidation.