PSI - Issue 59

Anatolii Klymenko et al. / Procedia Structural Integrity 59 (2024) 214–221 Anatolii Klymenko et al. / Structural Integrity Procedia 00 (2019) 000 – 000

219

6

Element, Weight %

O

Si

Ti

Cr

Mn

Fe

Ni

Mo

Pb

S1 S2 S3 S4 S6 S7 S8

25.47 13.76 23.78 12.33 14.86 21.22 30.44

- - - - - - -

- - - - - -

5.93 2.03 13.01 0.68 2.47 10.35 7.94 16.81

0.56 20.42

4.44 1.77 7.65 1.56 6.13 7,36 -

- - - - - - -

43.18 67.37 34.14 73.95 63.20 39.99 28.80

-

15.08

1.31 20.10

- -

13.05 8.45

9.46

0.79 21.51 0.70 24.77

S5 (BM) 1.48

0.69

0.49

1.40 63.68 12.00 2.38 1.08

Element, Weight %

O

Si

Ti

Cr

Mn

Fe

Ni

Mo

Pb

S1 (BM) 0.59

0.56- 0.42 17.67 1.43 65.18 11.86 2.99

-

S2 S3 S4 S5 S6

26.23 0.44

- - - - -

9.71

0.78 45.49

5.88

- - - - -

11.47 86.07 34.04 50.61 89.44

13.30 23.52 20.63 10.56

- - - -

-

- - - -

0.62 34.22 20.32

-

3.72 4.34

4.51 4.11 11.86

-

-

Element, Weight %

O

Si

Ti

Cr

Mn

Fe

Ni

Mo

Pb

S1 (BM) 3.01 0.59 0.44 16.49 1.09 48.96 9.79 - S2 (BM) 0.32 0.57 0.48 16.89 1.35 65.29 12.50 2.59 - S3 12.69 - - 1.80 - 6.70 1.76 - 77.05 S4 18.16 - - 13.37 1.89 35.25 5.71 - 25.61 S5 19.87 0.55 - 12.58 1.06 23.52 7.51 - 34.91 S6 13.84 - - 0.62 - 12.77 - - 72.77 S7 23.77 - - 8.70 0.86 31.38 2.21 - 33.07 19.64

Fig. 5. The micro-x-ray spectral analysis results after exposure of AISI 316L steel in lead melt for 240 (а), 720 (b) and 1440 h (c) at 450 °C.

According to the results, an increase of the duration tests from 240 to 1440 h at 450 °C is accompanied by a change in the structure of the corrosion products layer from uniformly formed over the base metal surface (Fig. 5a) mainly by lead, iron, chromium and nickel with characteristic inclined inclusions based on iron and lead, up to a three-layer sandwich formation (Fig. 5c). So, after 240 h of testing (Fig. 5a) an increase in the oxygen concentration is characteristic as the formation of the oxidizing layer: the minimum amount is in the base metal (1.48 wt.%), with an increase in the index in the direction from the near-surface layer at the interface "metal base/oxidation products" (12.33 wt.%) to the maximum concentration in the upper layers of corrosion products (30.44 wt.%). The presence of lead from a minimum (1.08 wt.%) to a fairly significant concentration (67.33 wt.%) in the near-surface layers of the base metal in the intergranular space of the metal base matrix as a result of intergranular corrosion due selective dissolution and mass transfer (diffusion) of alloying elements (nickel, chromium and manganese) from the metal base deep into the layer of corrosion products in the direction of the surface. After 720 h (Fig. 5b), the formation of an intermediate uniform layer at the interface "metal base/oxidation products" separation was observed, which differs from the base metal and the layer of oxidation products in terms of structure, elemental composition and their content, namely: the maximum concentration of oxygen (26.23 wt.%) and iron (45.49 wt.%), the presence of silicon (0.44 wt.%), manganese (0.78 wt.%), nickel (5.88 wt.%), chromium (9.77 wt.%) and a minor lead concentration (11.47 wt.%). After 1440 h (Fig. 5 с), the corrosion products take the form of a three layer sandwich formation with the characteristic growth of an unevenly distributed intermediate layer at the interface "metal base/oxidation products". The main (widest) layer, formed mainly by lead (up to 72.77 wt.%), is covered by a uniform surface layer, similar in elemental composition to the intermediate division at the border with a predominant iron content (31.38 wt.%) and insignificant, compared to the main layer, the concentration of lead (33.07 wt.%) and chromium (8.7 wt.%). There is also an increase in oxygen concentration from 0.32 wt.% in the main metal to 23.77 wt.% in the upper layers of corrosion products.