Processes and technologies of cold gas dynamic spraying of products agricultural equipment

Modern equipment of processing industry, animal husbandry, bioenergy complexes is used for processing, storage or transportation of aggressive substances. Functional coatings made of inert materials do not enter into any chemical reactions with food, processed products, livestock waste, acids and other aggressive media. There is a question of protection of the equipment of the processing industry, animal husbandry, bioenergy complexes from aggressive environments by application of processes of a cold gas-dynamic spraying. This is an urgent problem for the development of protective technologies and appropriate equipment for the implementation of the process of creating functional coatings

Application of cold gas dynamic spraying as an additive technology for producing materials based on nickel aluminide and titanium aluminide

Metal additive manufacturing is widely studied for its unique advantages over traditional manufacturing processes. It is used to form complex components of Ti, Fe or Ni alloys. However, for non-ferrous alloys – aluminum, magnesium, copper – additive technologies are not used due to rapid melting during laser, electron beam and/or arc treatment. Cold spraying is widely used as an effective technology for applying high quality coatings in the mass production of metal and alloy products and/or metal matrix composite coatings. In addition, cold spraying is a serious and effective tool for the additive manufacturing of metals, and research in this area is currently becoming intense. During heat treatment of materials obtained by cold spraying, new chemical compounds are formed – both intermetallic compounds and hardening ceramic inclusions that increase the microhardness. However, as a result of a change in the structure during chemical transformations, a change in the geometry of the product and the formation of pores can be observed.

Effect of roughness on the bond strength of decorative coating applied by cold gas-dynamic spraying

The adhesion strength of joints obtained by cold gas-dynamic spraying (CGDS) on cast iron base has been investigated. It is known that corrosion resistance of CGDS coatings is largely determined not only by the nature of the sprayed material, but also by its adhesion properties. This paper is a method for predicting the adhesion strength of a protective and decorative coating, which is a useful tool for engineers when studying the effect of certain technological parameters on the adhesion strength of cold gas-dynamic spraying. The results of an experimental study of pretreated surfaces and powder materials are presented. The optimum heating temperature was determined and a choice of material and method of substrate processing which ensures maximum adhesion strength under given technological conditions was substantiated. It was shown that the temperature of heating of the product surface essentially influences the adhesion strength of the coating. Besides the quality of the preprocessed surface is one of the factors providing the coating adhesion strength to the substrate. The dependences of the influence of the temperature of heating of the sample and the roughness of the surface on the adhesion strength are presented. The use of cold gas-dynamic spraying as a method providing high strength properties of copper and zinc protective-decorative coatings is proved.

CREATION OF ELECTRIC CONDUCTIVE COATINGS USING GAS-DYNAMIC SPRAYING

The article presents the results of research on the processes of creating conductive coatings based on copper and aluminum in order to determine the interaction of components on each other during cold gas-dynamic spraying (CGDS) and substantiate the method of introducing an additional component to obtain the desired composite coating. In particular, under conditions when the copper sputtering coefficient is almost zero (at a working air temperature of 300 °C), it is the search for the experimental dependence of the sputtering coefficient on the percentage of copper and aluminum powders in the sprayed mixture, determining their residual content in the coating and then calculating based on these data, the sputtering coefficients of copper and aluminum. The CGDS method obtained samples with composite coatings from mixtures of aluminum and copper powders at different initial mass concentrations of aluminum (from 0 to 100%, in increments of 10%) Other things being equal (air pressure 0,6 MPa, air heating temperature 300 ° C) . The spraying ratio of the mixture and the residual content of the components in the obtained composite coatings were measured. Data on the residual content of the components in the coating allows you to select the composition of the source powder required to obtain a given content of components in the coating. The dependences of the sputtering coefficients of copper and aluminum on the mass content of aluminum in the sprayed mixture are found. At an initial concentration of aluminum less than 66%. the coefficient of copper sputtering is higher than the coefficient of sputtering of aluminum. Both increase monotonically with increasing aluminum concentration until it reaches 61%. At high concentrations of aluminum (more than 66%) the spray coefficients of copper, aluminum and their mixtures coincide. The obtained data on the residual content of the components in the coating allows you to select the composition of the source powder required to obtain a given content of components in the coating. For example, the maximum residual copper content (~ 95%) can be obtained by adding to the source powder 30-40% aluminum. The obtained results confirm the interaction of the components on each other and justify the method of introducing an additional component to obtain a composite coating containing a component that is difficult to spray.

Modern processes and technologies of cold gas dynamic spraying of products agricultural equipment

Modern equipment of processing industry, animal husbandry, bioenergy complexes is used for processing, storage or transportation of aggressive substances. Functional coatings made of inert materials do not enter into any chemical reactions with food, processed products, livestock waste, acids and other aggressive media. There is a question of protection of the equipment of the processing industry, animal husbandry, bioenergy complexes from aggressive environments by application of processes of a cold gas-dynamic spraying. This is an urgent problem for the development of protective technologies and appropriate equipment for the implementation of the process of creating functional coatings

Microstructural Studies of the Copper-Based Coating Obtained by Cold Gas-Dynamic Spraying for the Restoration of Worn-Out Contact Wires

The microstructure of the coating obtained by cold gas-dynamic spraying was investigated. A Cu-Al2O3-Zn powder blend was sprayed onto a copper substrate to restore a worn copper contact wire. The coating thickness was 1–2.5 mm. Mechanisms of coating formation are discussed on the basis of microstructure studies. The relationship between the microstructure and the properties of the coating such as adhesion strength and electrical conductivity is shown. Improved adhesion strength was achieved through substrate surface preprocessing with coarse Al2O3 particles.

Вплив діаметру частинок порошку нікелю на їх швидкість і температуру при холодному газодинамічному напилюванні

To deposit coatings in cold gas-dynamic spraying (CS), a high-speed gas flow is used to accelerate and heat particles. Therefore, first of all, it is necessary to consider the general laws of the gas flow and the movement of particles in the flow, as well as its interaction with the substrate. Due to the CS process depends primarily on the particle velocity, it is important to understand the effect of the process parameters (pressure and temperature at the nozzle inlet), the characteristics of the powder particles (material density, shape, and size), and the geometry of the nozzle. The gas velocity limits the particle velocity that can be achieved with the CS process. Utilization of high gas pressure, long nozzles, and small particles lead to the fact that the particles move at a velocity close to the velocity of the gas, which can be increased by using gases with low molecular weight, as well as heating it. As a result of the analysis of theoretical and experimental methods for studying the cold spraying process, it was found that for coating formation velocity of powder particles needs to obtain a certain value (critical velocity), which depends on particle temperature at the impact, and density of the particle material. Numerical simulation of gas dynamics of a two-phase flow in CS nozzle and at the outlet from it for the range of air temperatures from 573 K to 873 K and constant pressure of 1,0 MPa has been carried out. The influence of the diameter of nickel powder particles on their temperature and velocity at impact was investigated. Numerical simulations were performed for a range of particle diameters from 5 to 30 μm. In the future, the results obtained can be used to find the optimal size of the powder particles under certain spraying conditions, to calculate the critical particle velocity, and also to develop the window of deposition. This will make it possible to select the optimal parameters of the gas flow at the nozzle inlet (pressure and temperature), which are guaranteed to ensure the adhesion of particles to the substrate and the formation of coatings. Also, the results obtained can be used to predict the properties of coatings, as well as to achieve maximum deposition efficiency of the CS process.

Corrosion resistant protective coating of the Zr–Nb–Sn system obtained by high speed cold gas dynamic spraying

The article presents the results of experimental studies on the creation of an optimal alloy composition of the Zr–Nb–Sn system for obtaining corrosion-resistant coatings using the technology of supersonic cold gas-dynamic spraying. Practical recommendations are given on the use of the developed coating in precision engineering products.