PSI - Issue 20

3

Borisova M.Z. et al. / Procedia Structural Integrity 20 (2019) 48–52 Borisova M.Z. et al. / Structural Integrity Procedia 00 (2019) 000 – 000

50

Fig. 1. Schematic illustration of the cored wire.

2

r



(1)

С





   

   

2 3 ( 2 2 (1   R r

 FeCr k Al O

1

))





Calculated by the above equation (1), the content of Al 2 O 3 in the powder wire was counted approximately as 10%. Refractory particles in the coating in our case, the inclusion of aluminum oxide, represent the main hardening phase of the wear-resistant coating. Due to the high melting point (2323 K), Al 2 O 3 particles at small spraying distances do not have time to completely melt and fall in separate splatters during arc deposition. The thickness of the deposited layer is about 300 μm for all modes of arc metallization. As can be seen from figure 2, the structure of the coatings is a typical layered structure of the coating is formed. It consists of separate layer-by-layer laid splatters – drops of the melt of the sprayed material, spread and hardened on the substrate. Metallographic analysis of transverse sections showed that the thickness of the layers varies in a wide range of ~1 – 40 microns. Since the arc metallization refractory additives of powder material are isolated as separate non-melted particles, the coatings are characterized by a heterogeneous microstructure, the cross-sections of the particles are predominantly ribbon shaped curved appearance. Etching with a 4% nitric acid solution revealed several colors and shades of structural components. Dominated by fragments of white color, which is interspersed with dark grey and black inclusions of different size and configuration.

Fig. 2. Microstructure of the coatings obtained on the 1-st (a), 2-nd (b) and 3-rd (c) spraying modes.

The study of the state with the identification of particles of the modifier and the matrix of wear-resistant coating of flux-cored wire with refractory additives was carried out by EDS analysis. The conducted analysis made it possible to identify different phases in the structure of coatings (Fig. 3). Element maps show the distribution of each element. In this figure is visible the chemical zonation for the elements Fe (green), O (red), Cr (cyan) and Al (blue). It is seen that the dark inclusions correspond to Al 2 O 3 , bright regions to ferrochromium, gray regions belong to ferrochromium with a high content of oxygen, i.e. they have subjected to the oxidation during an arc metallization.