OBRABOTKAMETALLOV Vol. 26 No. 2 2024 technology Coating was carried out by detonation gas dynamic spraying using a robotic complex (Fig. 1) for detonation spraying of coatings, consisting of a multi-chamber shaped-detonation device (MCDS), a gas post, a gantry robot, and a special powder feeder, which provides dosing and periodic powder feeding into the MCDS. Powder injection into the combustion chamber of the MCDS in the process of detonation of the combustible gas mixture ensures its heating and acceleration. Heated powders hit the substrate surface at high speed, creating a dense composite coating [23–25]. Ta b l e 1 Powders used for coatings Name, grade Manufacturer Method of obtaining Particle size distribution, µm d(10) d(50) d(90) Ti powder, PTS-1 JSC POLEMA Tula, Russia Amalgam metallurgy method 9.54 24.69 50.76 Al2O3 powder Donetsk Chemical Reagents Plant Initial material calcination in a halogen-containing atmosphere 2.28 19.96 46.36 Fe2O3 powder Donetsk Chemical Reagents Plant Utilization of thermal decomposition products of iron 0.23 5.54 27.9 Fig. 1. Robotic complex for detonation coating The right side of Figure 1 shows the assembling sheet of the coated baking oven. After coating all the heat-transferring surfaces of the oven components, the baking chamber is assembled. The baking chambers in the baking ovens of the Shebekinsky Machine-Building Plant are made of St3 steel. The finished baking oven of the Shebekinsky Machine-Building Plant is shown in Figure 2. A series of experimental specimens of coatings on a substrate of St3 steel with dimensions of 40×40 mm (3 specimens for each coating material) were fabricated to study the microstructure, phase composition, resistance to thermal cycling and emissivity. Before coating, the surface of experimental specimens was cleaned from oil contamination with hexane and subjected to sandblasting. Sandblasting was carried out at a pressure of 0.3 MPa with dry quartz sand with grain size 1–3 mm up to the 3rd class of purity according to GOST 9.402-82. Afterwards, residual
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