Papers by Keyword: Coating Thickness

Abstract: Hard nitride coatings has an important role for enhancing the wear resistance of metallic materials, thus increasing the life time of the products in industries. In this paper reviews the different methods of coating techniques, methods of PVD, mechanical properties of TiN coatings and wear resistance of titanium nitride-based coatings by physical vapor deposition (PVD) techniques. Thus the various approaches for enhancing the corrosion and wear resistance are categorized and summarized. The advantages, disadvantages and applications of Nitride based coatings are discussed.

Abstract: In the course of the study, several different methods of surface structural engineering are reviewed. The methods described in this paper are characterized by different process physics on the way to obtaining the result, but they are aimed at modifying the structure and properties of the surfaces to which they are applied. Among them, two different technological directions are considered. The first area involves technologies that include a friction component, namely thermofriction treatment (TFT) for thermofriction strengthening (TFS), additional thermofriction strengthening (ATFS) or thermofriction welding (TFW). The second direction is a technology that involves the use of an anode-cathode electrolysis mode in an alkaline-silicate electrolyte – micro-arc oxidation (MAO). The paper describes the features and results of the application of such technologies and the feasibility of using this or that method for materials of different classes, and presents schemes of the corresponding installations. The result of additional hardening of the surface of U8A steel from a microhardness level of 7.2 GPa to 14.7 GPa using the ATFS method after its thermal hardening to almost the maximum possible level is shown. The microstructure of the cross-section of a prehardened specimen of U8A steel after ATFS is presented, where the degree and nature of surface hardening are reliably visible. It is emphasized that in previous studies, consistently effective hardening of steels of various classes has been achieved, even up to the level of 22 GPa in 65G steel. Regarding the method of microarc oxidation, the structure and properties of coatings on low-alloy aluminum alloys AB and AD1 formed in an alkaline-silicate electrolyte in the anode-cathode MAO mode were investigated. It is shown that the method of MAO in alkaline-silicate electrolyte allows to obtain a coating thickness of up to 300 μm, a coating growth rate of ~ 2 μm/min, and a coating hardness of 10-20 GPa. The coatings have high adhesion to the substrate; they have a layered structure. The properties of the coatings are determined by the properties of the base layer. The coatings have a crystalline structure and consist of the following phases: γ-Al₂O₃, α-Al₂O₃, mullite (3Al₂O₃·2SіO₂), the ratio between the phases depends on the electrolysis conditions. It has been established that phase formation begins with the γ-Al₂O₃ phase, which in the process of further coating growth turns into the α-Al₂O₃ phase or interacts with silicon oxide to form the mullite phase.

Abstract: The article describes a method to improve the uniformity of electroplating using fuzzy logic. This method provides for the replacement of the non-stationary model of the process dynamics in distributed coordinates with the quasi-stationary model of the process dynamics in lumped coordinates. The production knowledge model with "IF-THEN" rules is developed for the stochastic influences taken into account. The dynamic choice of the defuzzification method is justified by solving the problem of minimizing the absolute deviation of the coating thickness average value obtained from the non-stationary model from the predicted value according to the quasi-stationary model at const values of stochastic influences. As an example, fuzzy control of the current for nickel coating is considered, taking into account the stochastic influence of the electroplating time, detail area, temperature and acidity of the electrolyte. The experimental results prove the effectiveness of the combined defuzzification method in comparison with their independent use in the control process.

Abstract: The article presents a study of the characteristics of experimental samples with a chrome coating: the straightness and ovality of the inner surface of the cylinder, as well as the hardness and thickness of the chrome coating. The chrome coating is obtained on a previously developed installation for applying chrome coating on the inner surfaces of hydraulic cylinders of hydraulic drives with hydrostatic guides. The measurement of the geometric characteristics of the internal surface of the samples was carried out, the values ​​of deviations from roundness and deviations from straightness were obtained. A study of the chrome coating was carried out, for this we cut out sectors from the samples, carried out their sample preparation, measured the hardness and took pictures under a microscope, measured the hardness and thickness of the chrome coating. The obtained measurement results: deviation from roundness, deviation from straightness, coating hardness, coating thickness - correspond to the specified technical requirements, the proposed construction of the installation for applying chrome coating to the inner surfaces and the electrolyte composition, selected earlier, are applicable for chrome plating of the inner surfaces.

Abstract: The article considers the influence of the surface geometry of a detail on the deposition of coating thickness in the simulation of electroplating processes. The methods for obtaining sets of points describing the surface of a detail are analyzed. Solving the inverse problem (recovering the 3D surface of a detail according to its 2D drawings) is the most promising method. The inverse problem solution is decomposed into simpler geometric problems: input data processing; obtaining primitives; obtaining the desired surface of a detail by applying logical operations to primitives. Mathematical statements are formulated and solution algorithms are proposed for solving these problems. The inverse problem solution is implemented through software. The distribution of the nickel coating thickness is shown for a detail, the surface of which is obtained by solving the inverse problem.

Abstract: Micro-arc oxidation (MAO) is known as a novel technique to use for the modifying the surface of valve metal, which improve mechanical and corrosion resistance properties. In this study, MAO coatings are fabricated on ALZ magnesium lithium alloy to protect the substrate from corrosion using environmentally friendly electrolytes under a high voltage power supply. The Taguchi method is used to identify the effects of current density, coating time and electrical frequency on the thickest coating uniformity. The optimum coating properties are characterized by coating thickness measurement, Scanning electron microscopy (SEM), Potentiodynamic polarization analysis. It was found that the processing time is the main factor affecting the thickest coating uniformity (t_u). Coatings fabricated under optimum conditions are in close agreement with the predicted values of Taguchi analysis. The corrosion resistance of MAO coated on ALZ magnesium lithium alloy are greatly improved compare to the bare alloy in corrosive environments.

Abstract: Friction surfacing is a solid-state coating technique process in which a mechtrode is rotated against the substrate under pressure, henceforth forming a coat on the substrate. This process not only can be used as coating process but it also provides flexibility in coating different materials as a revamp manufacturing process and it is suitable for getting excellent mechanical properties after the surfaced deposits. Bond strength is very good and these deposits are expected to serve better service life. The present work deals with mechtrode of SS-316, D3-tool steel and aa-2014 are coated on low carbon steel substrate by friction surfacing process and design of experiment were done by using taguchi L9 orthogonal array where the process parameters are mechtrode, rotational speed and traverse speed. The coating thickness, coating width and the SEM-microstructure analysis were studied.

Abstract: The development of hard coating based on colloidal silica nanoparticles on polymethyl methacrylate (PMMA) sheet was reported. The colloidal silica was surface-modified with methyltrimethoxysilane (MTMS) and formulated to hard coating solution via sol-gel process. The hard coating solution was applied to PMMA surface by spray deposition technique. Spraying process was carried out from spray nozzle outlet diameter of 0.35 mm and air compress pressure at 0.2 MPa with nozzle to substrate distance at 10 cm. The different coating thicknesses were obtained by adjusting the amount of coating applied. The optimal coating thickness that gives the highest pencil-hardness at 7H and 100% adhesion for adhesion tape test is 10 μm.

Abstract: The reinforced concretes are often exposed to severely corrosive environments such as sea water, contaminated water, acid rain and seashore etc.. Therefore, the reinforced steel bar embedded in the concrete is increasingly corroded in various environments mentioned above, and this corrosion problem is thought to be very important in terms of the safety and economic points of view. In this study, a multiple mortar test specimen(W/C:0.5) with variation of coating thickness was prepared and immerged in flowing seawater for five years. And, the effects of coating thickness affecting to cathodic polarization and cyclic voltammogram were investigated using electrochemical methods. The thinner coating thickness, both invasion and diffusion of dissolved oxygen, water and chloride ion on the surface of reinforced steel bar is more easily compared to the thicker coating thickness. Thus, at the beginning of immersion, the rate of corrosion in the case of the thinner coating thickness is higher than that of the thicker coating thickness. However, it is considered that corrosion products deposited on the surface due to higher corrosion rate played the role as a resistance polarization, and increased the diffusion layer, as a result, decreased the corrosion current density compared to the thicker coating thickness. Consequently, the relationship between corrosion current density and the coating thickness were not well in good agreement with each other due to the corrosion products after being immersed for 5 years. Therefore, in order to more optimum evaluate for corrosion possibility of the reinforced steel embedded in the concrete, not only corrosion potential but also other parameters such as coating thickness, W/C ratio, and other corrosion environment should be investigated in the case of immersed in seawater for long years.

Abstract: The objective of this research is to improve process capability and reduce production cost related to thickness of paint from Electro Deposition Painting (EDP) process. To achieve the objective, Six Sigma method was applied to find out the optimal setting of significant process factors, which are concentration of pigment in EDP paint, dipping time, and dipping voltage. Design of experiment technique with Central Composite Design type helped indicate the optimal setting of the three factors, which yielded the target EDP coating thickness with a minimal production cost. With this optimal setting, the process capability index (C_pk) increased from 0.61 to 1.99, and the production cost is expected to reduce by 1,730,498 THB per year.