PSI - Issue 72

Aleksandra Krstevska et al. / Procedia Structural Integrity 72 (2025) 172–180

177

Figure 4 Fracture location

Figure 5 Fracture of specimen 1

6.2. Hardness testing

The hardness testing, using HV10 method, was performed on 30 locations, separated on lower and upper zone. The measurement locations were presented on each zone: base materials, buttering layer of martensitic steel, HAZ regions and weld metal. A sample of the hardness distribution of the tested joints is given on Figure 6 and Figure 7. For the martensitic steel, the hardness values are within permissible range according to the standard ISO 15614-1 (International Organization for Standardization, 2017). The permissible values for this type of steel and affiliations in steel group in HAZ need to be < 350HV. The GOST 57423-2017 limits the hardness for 12X18H12T, maximum 186HV.

Lower zone

Upper zone

0 200 400 600

0 200 400 600

1 2 3 4 5 6 7 8 91011121314

1 2 3 4 5 6 7 8 91011121314

Measuring points

Measuring points

Hardness HV10

Hardness HV10

Specimen 2 250°C/-

Speciment 2 250°C/-

Specimen 3 250°C/760°C

Епрувета 3 250 ° C/760 ° C

Figure 6 Hardness distribution across lower welded dissimilar joint

Figure 7 Hardness distribution across upper welded dissimilar joint

6.3. Microstructural characterization For dissimilar welds of martensitic and austenitic steel, the most critical regions are the heat affected zone and fusion line region of the martensitic steel and the weld metal. The performed microstructural analysis is done to check for potential microstructural changes.