Theoretical Justification of Coating Adhesion during Gas-Thermal Spraying

The article provides a brief overview of modern methods of thermal spraying. Particular attention is paid to high-speed flame spraying. The theoretical substantiation of the adhesion of coatings formed on machine parts using the methods of thermal spraying is presented.

Modeling features of the technological process of forestry machines parts strengthening by the method of gas-thermal spraying

The efficiency of the working bodies of tillage forestry machines is determined by the sharpness of their soil-cutting elements. The purpose of the study is to substantiate the modes of the technological process of strengthening and recovery of cutting working forestry machines by the method of gas-flame spraying of wear-resistant coatings to increase their wear resistance and preserve the blade sharpness by implementing the self-sharpening effect, which allows increasing their life by 2-3 times. Technical and economic indicators of the gas-flame spraying process, as well as the scope of its application, depend on how well the technological modes of the spraying process are selected. The relevance of the topic is due to the need to increase the durability of tillage tools by strengthening their surfaces treatment. Such effective methods include the technology of recovery and strengthening of the working bodies of tillage machines using the technology of gas-flame spraying. In this regard, the issues of conducting research have become particularly relevant: to identify the relationships of technological parameters during the gas-flame application of wear-resistant coatings; to change the strength characteristics of the material of parts during their recovery, providing the necessary reliability and durability.

Experimental Study on the Stabilization Mechanism of Diffusion Flames in a Curved Impinging Spray Combustion Field in a Narrow Region

HVAF (High Velocity Air Flame) flame spraying can generate supersonic high-temperature gas jets, enabling thermal spraying at unprecedented speeds. However, there is a problem with the energy cost of this device. This study focused on combustors that used cheap liquid fuel (kerosene) as the fuel for HVAF. In this research, we have developed a compact combustor with a narrow channel as a heat source for the HVAF heat atomizer. Using this combustor, the stability of the flame formed in the combustor, the morphology of the flame, and the temperature behavior in the combustion chamber were investigated in detail. As a result, the magnitude of the swirling airflow had a great influence on the structure of the flame formed in the combustor, and the stable combustion range of the combustor could be determined. As the swirling air flow rate changes, the equivalent ratio of the entire combustor changes significantly, and the flame structure also transition from the premixed flame to the diffusion flame. From this study, it was confirmed that the temperature inside the combustor has great influence on the flame structure.

Production Technology and Damping Properties of Aerated Polymer Coatings

The process of obtaining aerated (filled with air bubbles) polymer coatings has been developed and investigated by the method of flame spraying with an assessment of their ability to damp vibrations. A technology for the controlled formation of aerated polymer coatings has been developed while using the capabilities of the ОИМ (OIM) 050 polymer thermal atomizer design which consists in providing a concurrent air flow between the flame torch and the jet of powder material. The experiments have been carried out with such thermoplastic polymers as polyethylene terephthalate, high pressure polyethylene, ultra high molecular weight polyethylene, polyamide. It has been found that the aeration coefficient grows almost in direct proportion with an increase in the amount of air in the concurrent flow for all investigated polymer coatings. It is noted that the aeration process is influenced by the rheological properties of liquid polymers, or rather, the value of the polymer melt flow rate. The limiting values of air in the concurrent flow have been determined, which make it possible not to reduce the adhesion of polymer coatings to steel substrates by less than 6 MPa and not to decrease their hardness by more than 25–30 %. Studies of the damping properties of samples with polymer coatings have been carried out on a stand, the kinematic diagram of which is based on loading the free end of a cantilever sample, abrupt removal of the load and registration of free damped oscillations by an induction-type contactless sensor connected to a computer. It is shown that the use of aeration when forming noise-absorbing coatings on steel samples can increase their logarithmic damping decrement by 18–26 %.

Fabrication of a Novel MgO-B2O3-SiO2-Zn Coating by Thermal Spraying

In automotive technology, the proper use of thermal insulation materials helps improve the performance and life of internal equipment and reduce maintenance cost. In this study, plasma spraying and flame spraying are used to prepare and coat a new MgO-B2O3-SiO2-Zn powder on the SUS304 substrate. The resulting coating as thermal insulation layer formed a networked microstructure between the substrates to improve the thermal insulation performance of the material. By validation of thermal radiation experiments, the thermal insulation effects of various ceramic powders were compared, the high-temperature and low-temperature thermal insulation materials for about 300 and 100 °C were determined, and the thermal insulation performance of the constructed material coatings was verified by analysis.

IMPROVEMENT OF THE SURFACE ALLOYING PROCESS OF CASTINGS USING GAS-FLAME SPRAYING

Comparative studies of the technology of surface alloying using gas-flame spraying and painting with alloying casting paint have been carried out. The research results are presented. A mode of surface alloying using gas-flame spraying has been developed.