جستجوی مقالات مرتبط با کلیدواژه "nanostructured coating" در نشریات گروه "مواد و متالورژی"

In this Study, PACVD (plasma assistant chemical vapor deposition) and Arc-PVD (cathodic arc physical vapor deposition) methods were used to deposit of DLC (diamond like carbon) on St37 steel. Then, an interlayer was performed before applying the main DLC coating using arc-PVD. Field emission scanning electron microscopy, x-ray diffraction, Raman spectroscopy, energy dispersive spectroscopy, adhesion and tribological tests were performed to characterize and evaluate of coatings. Many factors are responsible for the excellent wear and mechanical behaviors of the DLC PVD coating including the presence of TiCrAlN interlayer, the fine grains (30-40 nm), hardness gradient as well as Ti and Cr carbides. These factors, also led to reach the high adhesion for this coating. The grain size of DLC PACVD coating was measured approximately 70-110 nm. In addition the thickness of arc-PVD coating was less than that of the PACVD coating which caused lower internal stress and subsequently appropriate adhesion to the substrate. The results revealed that this coating had lower hardness and adhesion to the substrate than that of the DLC PVD.

In this study, corrosion behavior of nanostructured multilayer coatings of Ti/TiN applied on the 7075 aluminum substrate was evaluated by EIS method. Ti/TiN nano scale multilayer coatings were deposited on surface of samples by high-vacuum magnetron sputtering process, then structure and morphology of the coating were analyzed by using GIXRD, FESEM and AFM, afterwards, the corrosion behavior of coating was investigated by Nyquist and Bode phase curves after1, 12, 24, 48, 60 and 72 hours of immersion in 3.5% NaCl solution. Results show, the applying of nanostructured multilayer coating and interrupting columnar structure of TiN by the Ti as an intermediate layer causes to increase the impedance and corrosion resistance of Al7075 about 43 times compare with bare of Al7075, which proving that this coating is so effective for enhancing of corrosion behavior of Al7075

To improve mechanical properties of the 7075 Al alloy, alumina-zirconia nanostructured coatings were formed on it through Plasma Electrolytic Oxidation (PEO) operated in potentiostatic mode. The composite coatings were produced at 450V for 100-300s growth times in a stable electrolyte containing K2ZrF6. Phase evaluation of the layers coated at 200s and higher growth times proved alumina-zirconia layers comprising tetragonal zirconia (t-ZrO2) and  and -Al2O3 phases. Nanostructured alumina-zirconia coatings with 20-40 nm particles size, porous structure and increase in the porosity content by increasing growth times proved by microstructural investigation of the layers. The coating thickness was in the range of 12-19 m. The distribution of Al, Zr and O elements in the cross-section of the coatings was uniform. Significant enhancement in hardness for coated samples was achieved (about 10 times higher than bare samples).

In this study, hot corrosion behavior of two-types of plasma sprayed thermal barrier coatings (TBCs), was evaluated: a) usual CSZ (ceria-stabilized zirconia) and b) layer composite coating (CSZ/Nano-Al2O3). Hot corrosion test was carried out on the surface of coatings in sulfate and vanadate molten salts at 1050 °C for 40 h. Microstructures and various phases were examined by using scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses. As the results usual CSZ degraded, the formation of monoclinic ZrO2, rod type crystals of CeVO4, YVO4and semi-cubic crystals of CeO2 as hot corrosion products caused the degradation of mentioned TBC. Dense nano-alumina coating as an outer layer in layer composite coating reduced the infiltration of molten salts into TBC structure and resulted in the further resistance against hot corrosion.

In this study the effect of addition YSZ on structural properties and oxidation resistance of CoNiCrAlY/YSZ composite were investigated. CoNiCrAlY/YSZ composite powders produced by mechanical alloying process. Various amounts of YSZ particles (0%, 5%, 10% and 15 wt.%) were mixed with CoNiCrAlY powder and milled for 12, 24 and 36 h, then composite and commercial coating were deposited with high velocity oxy -fuel method on the inconel 617 substrate. The structural and mechanical evolutions of the coatings were evaluted using X-ray diffractometry, scanning electron microscopy and microhardness test. It was observed that by increasing YSZ content, porosity of coatings were increased and hardness of coatings were increased too. Also, addition of YSZ to CoNiCrAlY decreased the rate of grain growth in thermal spray process and heat treatment. Increase of porosity result to decreasing oxidation resistance of coatings.

TiCx coatings are well known for a very high melting point, high hardness, good corrosion and wear resistance, so, these properties have made them of particular interest for a broadrange of application industries. In this research, nanostructured TiC was coated onto H11 hot-working steel at three different operating temperatures, such as 470, 490 and 510 (as a thermodynamic- kinetic parameter), by the pulsed DC plasma-assisted chemical vapor deposition (PACVD) method. The phase and structure properties and corrosion behavior of thin film were studied by X-Ray direction, X-ray photoelectron spectroscopy (XPS), raman spectroscopy, SEM, Polarization test and EIS. The results indicate that coating which was applied at 490 °C shows the formation of a homogeneous and uniform layer with particle size of about 7 nm and high corrosion resistance, and its corrosion behaviors possessed the positive open circuit potential (OCP) of about 10 mV vs. Standard calomel electrode (SCE) and lowest current density of about 0.43 (μA/Cm-2) in 3.5% NaCl solution.