Materials Science Forum Vol. 1083

Abstract: The physicomechanical properties and morphology of composite electrochemical coatings (CEC) nickel-cobalt-nanodiamond from a chloride electrolyte-colloid of optimal composition have been investigated. For this CEC, microhardness (21-25 GPa) and internal compressive stresses (150-210 GPa) were determined. The study of wear and the Corrodcoot-test of the CEC showed a higher wear resistance (1,5 times) and the protective ability (2-3 times) of the CEC in comparison with chrome coatings. Studies of the CEC morphology and the nickel-cobalt alloy showed that the roughness of the resulting deposits, in comparison with nickel coatings, is 10 times less, and the fractal dimension of the coating surface is of the greatest importance. The cubic type of the nickel-cobalt-nanodiamond CEC lattice is established. The leveling effect on the structure of galvanic deposits of nanodiamond introduced from outside, as well as of microheterogeneous nickel and cobalt compounds formed in the electrolyte-colloid, has been determined.

Abstract: One of the most effective means of protecting metalwork equipment premises from corrosion is currently zinc-plating. Zinc-plating increases the service life of the equipment by 2-3 times, i.e. up to 20 years, which makes this method economically justified.We measured the electrode potentials and corrosion current between two plates – steel and zinc, depending on the size of the zinc plate. Modeling of the corrosion process with a decrease in the zinc coating was carried out by reducing the area of the zinc plate. At the same time, the area of the steel plate was constant. The protective ability of the zinc coating is maintained as long as it occupies at least 10% of the surface area of the steel product. Reducing the area of the zinc coating leads to catastrophic corrosion failure of the coating.

Abstract: The article discusses a technique for assessing the collision probability of particles of dissimilar materials in the process of detonation spraying of composite coatings. In consequence of different properties of initial powder materials (mass, aerodynamic resistance), quality indicators of composite coatings are determined not only with motion parameters of particles but with their mutual position in the flow of detonation products. In the case of using reactive components, interaction of molten particles in the flow can lead to chemical reactions, formation new materials on the substrate, heterogeneous structure of the coating, and deterioration its strength and adhesive properties. Preliminary quantitative assessment of the probability of collision of particles before their contact with the surface of the product affords to make a conclusion about deviation of quantitative indicators of the surface from supposed ones before full-scale tests.

Abstract: Inner surface of tanks is subject to corrosion due to constant contact with aggressive medium. The greatest danger from the point of view of possible corrosion destruction of steel is water (bottom, lower belts of the tank) and gas-air mixture (roof, upper belt) due to saturation with aggressive components: hydrogen sulfide, carbon dioxide, salts. Failure statistics show that the main reason for the failure of oil tanks (about 70%) is the corrosive wear of the surface that comes into contact with the aggressive medium. The application of paint coatings on the internal surfaces of steel tanks for the storage of oil and oil products is an effective measure to reduce corrosion and increase the life of tanks. However, there are a great many coatings. From the experience of tank operation, paint coatings of the following types were selected to analyze the effectiveness of corrosion protection: XC-717, EP-0020, FL-777, VN-780. To select the paint coating of the inner surface of the tank, physical and mechanical parameters were determined and calculations of the corrosion rate of the tank walls for the above paint coatings were carried out. After physical and mechanical tests, it was established that the best values of the coating are EP-0020. Thus, it is recommended to use a EP-0020 coating as a passive protection of the inner surface to ensure the durability of the tanks.

Abstract: In this paper, it is proposed to investigate the influence of the parameter providing the rate of pipeline coating degradation on the protective length of cathodic protection systems (CPS). Comparison of the calculated values of the pipeline coating resistance with the predicted values is carried out according to the theoretical distribution of the pipeline coating resistance in time. The difference between the practical value of the parameter providing the rate of coating degradation of the considered pipeline section from the predicted one is determined. The dependence of the parameter providing the rate of pipeline coating degradation on the protective length of the CPS has been formed, which makes it possible to reduce the number of cathodic protection stations along the pipeline path at the design stage, and to diminish their energy consumption in the electrochemical protection system from corrosion of oil and gas pipelines.

Abstract: The work discusses the problem of development of a heat-protective coating for objects of various purposes which are subjected to the external high-temperature impact. As a solution of the problem the application of heat-absorbing components providing the thermal barrier effect conducing to refraction of heat flows directed to heating of the protected object in the recipe of a heat-protective coating is presented. Temperature conditions of the protected object are provided due to the endothermic reaction which passes in the heat-protective layer by reaching the temperature of the selected component decomposition. Besides, the temperature of the heat absorption reaction has to be lower than the lesion temperature of the protected object.

Abstract: Full functioning of wells in oil and gas fields is impossible without the use of tubing. Main function of tubing is transportation of gases and liquids produced in productive zone to well surface. In addition, tubing acts as a kind of insulator that protects the gas and liquid transported through them from the walls of the well, and also prevents the occurrence and development of corrosion, deposits of paraffin and asphaltene on casing pipes. The tubing pipe placed in the well is also necessary in order to ensure the carrying out of downhill and repair work, which is regularly necessary. Standard tubin g (tubing) as a result of technological difficulties does not undergo a strengthening operation. When manufacturing tubing and locks to them from alloyed steels, the main attention is paid to improving mechanical properties, which is achieved by thermal and chemical-thermal treatment. However, the practice of operating tubing shows that the introduction of these measures does not solve the issue of reliability, since threaded connections for the coupling and nipple remain vulnerable sections of tubing. Tubing (tubing) during its operation experiences significant loads and is in constant contact with aggressive media, which leads to serious requirements for their quality. The possibility of replacing its production from alloyed steels with aluminum alloys, for example, AlCuMg₂ will facilitate the design by 2.5 times, prevent the tendency to stress corrosion cracking (SCC) in a hydrogen sulfide-containing medium and eliminate inhibitory protection. The main disadvantage of aluminum alloys is the tendency to pitting corrosion. It is possible to improve the protective properties of the passive film on aluminum alloys by anodizing.

Abstract: The experimental results of obtaining complex-alloyed intermetallic alloys by the method of liquid-phase self-propagating high-temperature synthesis (SHS) and their subsequent use for the formation of wear-resistant coatings by the method of electrospark deposition (ESD) are submitted. Metal oxides Cr2O3, NiO, CoO and mineral concentrate containing a larger part of ZrO2 in its composition were used as a melt charge for the SHS experiments. Alloys based on Ni-Al system dopped with Cr, Zr, Co, and C were obtained. It was established that extra addition of C led to the refinement of the alloys microstructure (3-5 times). ESD coatings were formed on steel 45 using the obtained alloys as anode material. The coatings formed by using the alloys doped by Co, Zr, Cr and extra addition of C (0.4 wt%) proved to be maximum wear resistant.

Abstract: The hardening of hard alloy WCo8 was performed by continuous laser radiation with a laser beam of 1 mm/min diameter, laser radiation power of 200 W, and different speeds of laser beam movement. After laser treatment of hard alloy WCo8, diamond-abrasive wear tests were performed. Duration of the tests varied: 3–6–9 minutes; then the wear, intensity of wear, wear rate were calculated. The analytical dependences of determining the diamond-abrasive wear of hard alloy WCo8 depending on three parameters (power, laser beam propagation speed and duration of the diamond-abrasive wear process) were evaluated. There are no methodological difficulties in applying those dependencies, therefore we get high reliability of the results obtained in that case and the possibility to further calculate the effect of increasing the power and speed of laser radiation on the diamond-abrasive wear.

Abstract: It is demonstrated that using the mathematical formalism of the interaction parameters for multicomponent metallic solution, it is possible to predict mass transfer in a system consisting of two dissimilar metals separated by low-melting one containing non-metallic impurities. The calculation of the interaction parameters in three-and four-component systems was carried out using the equations of the coordination-cluster model. Comparison between theory and data reported in the literature for corrosion in sodium loop led to the conclusion about the most probable mechanism of the influence of the oxygen impurity content on the corrosion rate of iron under non-isothermal conditions.