PSI - Issue 40

Ekaterina A. Kazantseva et al. / Procedia Structural Integrity 40 (2022) 207–213 Kazantseva E.A. and Komarova E.G. / Structural Integrity Procedia 00 (2022) 000 – 000

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with the substrate. Then, the main CaP layer contains the multiple branched rounds and elliptic pores inhomogeneously distributed over the coating’s thickness of 50 -60 μm. Finally, the outer CaP layer is represented by the structural spheroidal elements (spheres) with internal pores and outer pores between the spheres (Fig. 2). At the same time, the surface of the UMAO coatings includes the areas with structural elements as well as the local fracture areas containing destroyed spheres and fragments. This is due to the mechanical and cavitation effects of the US cause damage to the growth of spheroidal structural elements (Qu et.al., 2013).

(a)

(b)

(c)

Fig. 1. SEM images of the coating ’s cross-section and EDX scan lines of the elements (O, P, Ti, Ca) distribution throughout the thickness of the (a) MAO-coating, (b) MAO/PUS-coating, (c) MAO/US-coating.

EDX analysis indicates the following elemental composition in all the coatings: O, P, Ti, Ca (Fig. 1, Table 1). The presence of O, P, and Ca is a consequence of the transport of substances in the channel of plasma micro discharges from the electrolyte to the processed sample and further interaction between them (Mashtalyar et.al. 2020). For all the coatings, the EDX scan lines are characterized by the intensive fluctuations, which may be due to the peculiarities of the internal porous structure, as well as due to the inhomogeneous elemental distribution throughout the coating’s thicknes s. In addition, the elemental distribution throughout the thickness of all the coatings changes according to the following description: Ca concentration increases (blue line), Ti concentration decreases (violet line), P and O lines are much fluctuated (red and green lines, respectively), which make their qualitative analysis difficult. Such a trend occurred due to the firstly negatively charged phosphate ions in the electrolyte deposited on the positively charged specimen (anode). After changing the electric charge on the surface of the growing coating, positively charged calcium ions also settle into the coating.

Table 1. Quantitative elemental composition of the UMAO coatings.

Elements amount in the coating cross-section ( at. % )

Elements amount on the coating surface ( at. % )

Element

MAO

MAO/PUS 69.6 ± 2.3 14.7 ± 1.0 11.3 ± 1.0

MAO/US 68.8 ± 2.9 15.9 ± 0.9 11.4 ± 0.7 3.9 ± 0.5

MAO

MAO/PUS 69.6 ± 3.1 14.7 ± 0.7 11.1 ± 0.6

MAO/US 68.7 ± 2.6 15.4 ± 0.8 11.0 ± 0.9 4.8 ± 0.4

O Kα P Kα Ti Kα Ca Kα

66.1 ± 2.9 16.2 ± 1.4 13.5 ± 1.1 4.2 ± 0.2

69.7 ± 3.2 14.9 ± 0.6 10.9 ± 0.8 4.5 ± 0.2

4.5 ± 0.4

4.6 ± 0.2

Ca/P

0.3

0.3

0.2

0.3

0.3

0.3