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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The magnitude of microdeformations in copper with an increase in the nozzle displacement step decreases slightly (0.17% and 0.119%), which may be due to a decrease in the exposure time of corundum particles to the metal (42 s and 24 s). A microspectral analysis of the surface of the coating applied when the nozzle was displaced by 2 mm, carried out separately for copper and zinc particles, as well as along the route including two copper particles and a zinc particle, shows the presence of preferential diffusion of copper into zinc Fig. 2.

Fig. 2. The distribution of elements in particles of copper and zinc: 1 is copper, 2 is zinc.

As can be seen from the obtained data, the diffusion of copper is almost the same on both sides of the zinc particle and the copper concentration in zinc decreases to 16.30 at.% on the one side and to 18.94 at.% on the other side of the zinc particle. In the middle of the zinc particle, the copper content rises to 25.56 at.%, which is associated with the process of interdiffusion. With (reactive) interdiffusion, measuring the depth of diffusion layer, we can determine the diffusion coefficient by the formula by Bokstein (1978): D = Х 2 /2t , (1) Using the maximum exposure time of the particles and heated air stream to the surface when the nozzle is displaced by 2 mm (42 s) and 3 mm (24 s), using the formula, we can calculate the distance over which the components diffused. The diffusion coefficient from a liquid melt of zinc to copper at a temperature of 427° С is ≈ 0.45 х 10 -9 cm 2 /s by Smitls (1980). Substituting the value of the diffusion coefficient and the process time (24 s and 42 s), we find that the diffusion does not exceed 970 nm, which is significantly less than the results obtained Fig. 2. The calculation of the diffusion coefficient at a particle length (path) of 15.88 μ m shows Fig. 2 that with a minimum process time it is ≈ 2.25 х 10 -8 cm 2 /s, and with a maximum effect of a particle flow ≈ 0.75 х 10 -8 cm 2 /s. For analysis, you can use the results obtained in the study of the diffusion of components in the system copper – zinc (brass). The diffusion coefficient of zinc into copper for the γ phase at a temperature of 350° С is ≈ 1.3 х 10 -9 cm 2 /s by Zite (1958). It has been theoretically and practically proven that the diffusion coefficient of zinc into copper is several times greater than the diffusion coefficient of copper into zinc; sometimes this relationship, for example, calculated for the ε phase, is abnormal (D Zn :D Cu = 47) by Zite (1958). In this case, the diffusion coefficient obtained in this work has an abnormal character and can be given the following explanation. Under the direct influence of the directional air flow with the deposition parameters used, the coating is for ≈ 0.6 s; at this time, its temperature rises and amounts to 80-90% of the air flow temperature ( ≈ 450° С ) with a slight decrease to the substrate by Arkhipov et