Structure Formation In Coatings Research Articles

Formation of Corrosion‐Resistant Nitride Coatings Based on Ti–Al–Cr–Fe–Ni High‐Entropy Alloy

The purpose of the work is to study the features of the phase and structure formation of coatings (Ti–Al–Cr–Fe–Ni)N formed by vacuum arc deposition and to study the influence of technological parameters of the deposition process on their corrosive properties. It is established that on the basis of the selected elements, it is possible to form a high‐entropy compound in the form of a solid solution. The structure of nitride coatings based on high‐entropy compounds formed by vacuum arc deposition is studied. It is established that the phase composition of coatings largely depends on the ratio of titanium and aluminum, which is determined by the technological parameters of deposition. An analysis of the results of the electrochemical behavior of coatings (Al,Ti,Fe,Cr,Ni)N shows that an increase in the corrosion resistance of these coatings is due to the synergistic effect of the formation of a solid substitution solution with a dense nanoscale structure and an increased relative aluminum content in them.

Particle/substrate interaction and coating structure formation during detonation spraying of copper powder on steel

Particle/substrate interaction and coating structure formation during detonation spraying of copper powder on steel

Structure Formation of Diamond-Containing Coatings during Sintering of Specially-Shaped Grinding Wheels

In this work, the structure formation of powder diamond-containing coatings with Sn-Cu-Co binders during sintering of specially-shaped grinding wheels has been studied. The kinetics of structure formation was studied using diamond-free metallic binders and diamond-containing samples. Powder components of the coatings were mixed with an organic plasticizer and applied on steel workpieces by rolling. Sintering was performed in vacuum at 700–820 °C. The microstructure, phase composition, and distribution of elements in metallic binders and interface layers between the binders and steel base were studied. The morphology of the surface and structure of fractures of the diamond-containing samples have been examined. Stages of structure formation of the coatings during heating and sintering have been found. At 700–780 °C, diffusion of tin into copper particles plays the key role in the structure formation of the coatings. Dissolution-reprecipitation of cobalt at 780–820 °C has a significant effect on formation of the coating structure and interface layers between the coating and steel base.

Structure and Tribological Properties of Ni–Cr–Al-Based Gradient Coating Prepared by Detonation Spraying

In this paper, Ni–Cr–Al coatings were deposited using the detonation spraying method. The aim was to investigate how technological parameters influence coating structure formation, phase composition and tribological performances. We observed that the degree to which the barrel is filled with an O2/C2H2 gas mixture strongly influences the chemical composition of manufactured coatings. High degrees of barrel filling led to a decrease in aluminum content in the coating. Filling degrees of 40% and 50% produced sprayed coatings in which only Ni–Cr phases could be found. When the filling degree was reduced up to 25%, Ni–Al phases began to form in the sprayed coatings. Gradient Ni–Cr–Al coatings were produced by gradually reducing the filling degree from 50% to 25%. These coatings are characterized by Ni–Cr near the substrate level with Ni–Cr and Ni–Al phases at higher levels. The results obtained confirm that gradient Ni–Cr–Al coatings exhibit high hardness as well as good wear resistance.

Structure formation of coatings based on Cr, Hf, Ti, Ta, W, Zr and carbon with gradient change of the components concentrations

Structure formation of coatings based on Cr, Hf, Ti, Ta, W, Zr and carbon with gradient change of the components concentrations

A Study of the Processes of Structure Formation in Ceramic Coatings by the Kinetic Monte Carlo Method

The processes of structure formation in arc-PVD Ti–Cr–N coatings are studied by computer simulation methods. A new approach to defining the geometric space for determining the positions of atoms relative to the formed dimers and crystallites is proposed. The structure parameters are calculated, and the processes of structure formation in coatings at a potential of 120 V are studied.

ВЛИЯНИЕ РЕЖИМОВ НАПЛАВКИ НА ХАРАКТЕРИСТИКИ ТЕПЛОМАССОПЕРЕНОСА ЭЛЕКТРОДНОГО МЕТАЛЛА, ФОРМИРОВАНИЕ СТРУКТУРЫ И СВОЙСТВ ПОКРЫТИЙ

The peculiarities of structure formation in coatings deposited under conditions of controlled heat and mass transfer with the pulse change of power parameters of the mode are considered. 
 It is shown that as a result of the pulse control of mode power parameters, in a coating there is observed of structural heterogeneity decrease on a coating section at the expense of the decrease of structural constituent dimensions in it that increases considerably of operation properties of strengthened products operated under conditions of low temperatures of the extreme North. The investigations are carried out with the use of the complex of fast processes of heat and mass transfer that ensured high productivity of the investigation process at lower cost of time and material costs. 
 It is recommended for a wide range of experts in the field of modern physical material science, hydrodynamics, chemistry and mechanics of a deformable solid, reliability and technogenic safety, control of fast processes of the formation of permanent connections modified with pulse high-energy impact.

Особенности формирования структуры покрытий из латуни на поверхности алюминиевых сплавов методом фрикционной перемешивающей обработки

Особенности формирования структуры покрытий из латуни на поверхности алюминиевых сплавов методом фрикционной перемешивающей обработки

Thermodynamic Approach to Assessing the Curing of Protective and Decorative Coatings of Exterior Walls of Buildings

The values of the system energy change caused by the structure formation of coatings based on paints using mineral binders are given. It is established that the process of curing coatings can be described using the first law of thermodynamics and thermodynamic potential - enthalpy. The main regularities of changes in thermodynamic parameters in the process of curing coatings on cement concretes depending on the curing time, the porosity of the substrate is revealed. It has been established that, depending on the type of coatings, there is an unequal change in the energy of structure formation, which allows predetermining the different operational durability of coatings. It is shown that the smallest change in entropy during the curing process is characteristic of coatings on substrates characterized by lower surface porosity. The increase in entropy in the process of curing coatings on substrates with high porosity suggests that the coatings are characterized by a greater defectiveness and, consequently, a greater probability of their destruction during operation. The increase in the surface porosity of the cement substrate reduces the adhesion strength of the coatings and reduces its durability during exposure to the environment.

Special Features of the Structure of Titanium Nitride Coatings in Substrate Surface Cuts

Elemental compositions and structure-phase states of titanium nitride coatings on the flat surface and in a cut of substrate from 10Cr18Ni10Ti steel are investigated by the methods of x-ray microspectral analysis, Auger electron spectroscopy, and dark-field electron microscopy analysis of the bending-torsion of the crystal lattice. It is established that the coating in the cut, unlike the coating on the frontal surface, has a modified elemental composition and a two-layer structure whose special features and thicknesses change with distance from the sample surface. It is shown that these changes are caused by phase transformations, decreased number of defects, dispersion of layer structures, and increased concentration of impurities with increasing distance from the substrate surface. Based on the results obtained, possible conditions for coating structure formation in the cut of the substrate surface are discussed.

Features of Gas-Thermal Coating Structure Formed by HVAF Method from Powder Material Based on Fe–Cr14–Ni6–Si3

Expansion of gas-thermal spraying technology applications in various industries such as oil and gas, chemical, mechanical engineering, aviation, rocket building, agro-industrial, etc., can be achieved by obtaining a given set of operating properties with control of coating structure and phase composition. Direct control of the coating structural and phase composition is only possible after a complete establishment of a relationship between the factors determining the structural inheritance of the initial powder material and factors that influence a change during the coating deposition. Parameters and regimes of gas-thermal deposition technology should be substantiated not only empirically, but also scientifically. These processes have not been sufficiently studied in a materials science respect. In addition, information provided by raw material producers (fractional composition, chemical composition, powder material production technology, and less often flow parameters and bulk density) is not provided in its entirety. This work demonstrates the relationship between powder material production technology and features of coating structure formation by the High Velocity Air-Fuel (HVAF) deposition process of Fe-Cr14-Ni6-Si3 (iron-based) powder material used extensively in the oil and gas industry.

Localisation of deformation in cold gas dynamic spraying

One of the main specific features of the cold spray process is localisation during particle impact deformation. The resultant adiabatic shear instability is the phenomenon that is known to play a major role in the particle/substrate and particle/particle bonding and coating structure formation during the cold spray process. In this article, the cold spray process is numerically simulated as an impact between a single spherical particle with the substrate, and comparison with experimental results for Armco iron and stainless steel particles is made. To describe a deformation behavior of the two materials at high strain rates, the Johnson–Cook model has been chosen. The results indicate that the model accurately captures the grain distortion in the impact zone for both materials. This approach provides valuable information on the characterisation of the strain localisation at the particle/substrate interface.

Structure formation in coatings during laser welding

Structure formation in the surface layer of steel 20 during the laser welding of steel H13 (analog #4Kh5MF1S#), which was performed using a LENS 850-R installation with a laser having power of 1 kW by several standard schemes, is investigated. The influence of welding technology on the formation of a nonuniform structure and hardness by the welding layers is investigated. Metallographic, spectral, and X-ray structural analyses are performed. A considerable variation in the chemical composition of layers compared with the chemical composition of the initial steel H13 is shown. Welding heating at 650 and 750°C leads to the structure leveling and the hardness lowering. The factors affecting the complex character of structure formation and, correspondingly, variations in microhardness for all types of welding are revealed.

Air Gas Dynamic Spraying of Powder Mixtures: Theory and Application

The radial injection gas dynamic spray (RIGDS) technology of powder coatings deposition was considered for this work. A coating was created by injecting powders with variable compositions into a supersonic air jet and depositing powder on the substrate. This study describes the preliminary analysis of an air gas dynamic spray method realized by a portable RIGDS apparatus with a radial injection of powder. Attention was given to shock compaction processes during the coating structure formation and examples of powder mixtures utilization in RIGDS. It was shown that the operational parameters of supersonic powder-gas jet have a significant influence on the coating's microstructure, thus defining the high performance of the coating. Compaction and bonding of particles were analyzed.

Effect of Properties of Titanium Aluminide Powders and Detonation Spraying Conditions on Phase and Structure Formation in Coatings

We have studied phase formation in detonation coatings sprayed from Ti - 50 at.% Al powders. The powders of the alloy were obtained by various methods: crushing an ingot and mechanical alloying of Ti and Al. Using polyphase nanostructural materials activated by mechanical alloying makes the process of phase formation in the gas-thermal sprayed coatings based on them more general-purpose and controlled due to the more active and more subtle reaction of the material with the gaseous atmosphere. We have shown that from mechanically alloyed Ti - 50 at.% Al powder, using the detonation-gas spraying method we can consolidate a coating based on Al2TiO5 by oxidizing action of the working gas on the powder and also a coating based on titanium aluminides with TiN inclusions by nitriding action. The phase composition of the cast microstructural γ-TiAl powder is inherited by the coating.

Computer simulation and control of plasma spraying processes

An integrated technological system for modeling, experimental study, and practical realization of plasma spraying process was devised. The system provided simulation of the main plasma spraying process stages (heating and acceleration of particles in a plasma jet, coating structure formation, heat transfer, and stress–strain state in a coating–substrate system); experimental measurement of the main plasma spray characteristics and entering them in a computer in a real time mode; computer control of the spraying process; and plasma spray coating corresponding with the devised technological process. This integrated system was upon the basis of vacuum plasma spraying “Plasmatechnik” equipment. An original opto-electronic system was used for experimental measurement of temperature, particle velocity, and coating temperature.

Morphology and Hardness of a Steel Surface Layer after Electric-Spark Alloying with TiN ― Ni Alloys

Features of forming a coating surface with electric-spark alloying and TiN ― Ni alloy electrode materials are established. Analysis of coating morphology makes it possible to draw conclusions about the discrete nature of coating structure formation. Features of the interaction of deposited material with the anode due to changes in the phase composition and electrode structure are established.

Substrate–coating thermal interaction during high velocity oxyfuel spraying

AbstractThe mathematical simulation of the thermal interaction between a 34Cr–4Mo steel substrate (UNS-G41350) and a coating formedfrom droplets of WC–12Co powder particles during high velocity oxyfuel (HVOF) spraying is undertaken in the present paper. Analysis of the heat transfer processes permitted investigation of temperature evolution, coating solidification, substrate fusion and solidification, and in particular features of the thermal interactions between the substrate and the coating as well as the coating layers. The analysis also allowed the optimal conditions of the substrate and coating structure formation to be estimated. The results obtained are used in Part 2 of this paper (to be published later) to predict the structural parameters, which are then compared with the experimental data.MST/3039

Interacción térmica recubrimiento-sustrato en la proyección a alta velocidad (HVOF) de partículas (polvo) de WC-Co

The mathematical simulation of the thermal interaction between a 34CrMo4 (UNS-G41350) steel substrate and a coating formed by the droplets of WC-12 % Co powder particles during HVOF spraying is undertaken. Analysis of the heat transfer processes permitted the investigation of the temperature evolution, coating solidification, substrate fusion and solidification, particular features of the thermal interactions between the substrate and the coating as well as between the successive coating layers. The analysis has also permitted to estimate the optimal conditions of the substrate and the coating structure formation. The obtained results were used in subsequent articles to predict the structure parameters, which agree with the experimental data.