PSI - Issue 20

Vladimir Arkhipov et al. / Procedia Structural Integrity 20 (2019) 124–129 Vladimir Arkhipov et al. / Structural Integrity Procedia 00 (2019) 000–000

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seal the coating and increase the cohesive strength of the applied metal layer by Moskvitin (2018). During deposition, the main technological factors that influence the formation of the structure and properties of the coating are the air flow temperature and the time of exposure of the particle flow to the surface. Increasing the temperature of the air flow increases the speed of the particles, which, accordingly, affects the amount of deformation of the metal particles. At the same time, heating the coating with an air flow leads to a change in the structure and substructure in the deformed metal (recovery, polygonization). The time of exposure of a stream of particles and heated air to the surface affects the degree of deformation of ductile particles of metals and the completeness of the process of restructuring the structure and substructure by Arkhipov et al. (2017).

Nomenclature d

lattice spacing, nm

D diffusion coefficient, cm 2 /s D Zn :D Cu diffusion coefficient of copper into zinc К over

overlapping factor of nozzle displacement, % nozzle displacement towards previously applied layer, mm

l

L S

nozzle exit to sprayed surface distance, mm

surface area, mm 2

t

diffusion process time, s

Т V X

air flow temperature at nozzle entrance, ° С rate of nozzle movement toward sprayed surface, mm/s

average depth of diffusion layer (a half-depth of diffusion layer shall be taken for calculations), cm

2. The methodology of the experiment Coatings deposited on the surface of samples of steel 40X by the method of gas-dynamic deposition using the finished mechanical mixture of particles of copper, zinc and aluminum oxide (corundum) in a ratio by weight of Cu:Zn:Al 2 O 3 = 35%:35%:30% (grade C – 01–11). The coating is applied at the nozzle movement speed relative to the surface V = 10 mm/s; distance L = 10 mm from the nozzle section to the sample size 15x15x3 mm using the air flow heated to t ≈ 450°C. With this method of deposition, moving the nozzle along the surface of the sample makes it possible to apply a metal layer of ≈ 5.6 mm wide in the shape of a circle segment. To spray a uniform thickness over the entire sample surface, the nozzle is displaced relative to the previously applied metal layer by a certain distance (l) and the next layer is applied when the nozzle moves back. The operation is repeated sequentially until the coating is applied to the entire surface. For research, samples were sprayed with a nozzle offset of 2 mm (overlap ≈ 64%, Fig. 1) and 3 mm (overlap ≈ 55%). The coating time on the entire surface (S = 225 mm 2 ) in the first case is ≈ 14 s, and in the second ≈ 12 s. A graphical estimate of the influence of the overlap coefficient shows that when the nozzle is displaced by 2 mm (K over ≈ 64%), there are surface areas that are exposed to the flow of air and particles in the second (28 s, S = 90 mm 2 , Fig. 1, position 3) and the third times (42 s, S = 112.5 mm 2 , Fig. 1, position 4). When the nozzle is displaced by 3 mm (K over ≈ 55%), the surface has a more uniform treatment; ≈ 66% of the sample area is subjected to repeated exposure to particles and heated air (24 s, S = 148.5 mm 2 ).