PSI - Issue 72

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

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a) without post weld heat treatment

b) with post weld heat treatment

Figure 8 Microstructure of base material X10CrMoVNb9-1

Figure 9 Microstructure of base material 12X18H12T

The microstructure of the martensitic steel is a fine-grained structure with high strength, low ductility and high creep resistance, Figure 8. The austenitic microstructure of 12X18H12T provides high ductility, strength and excellent creep resistance, Figure 9.

Weld metal – joint 2 with X10CrMoVNb9-1

Weld metal – joint 3 with X10CrMoVNb9-1

Figure 10 Microstructure of weld metal

As presented on Figure 10, the weld metal has austenitic structure without Cr carbide zone. This Cr carbide zone represent brittle zone, especially in the martensitic weld deposit transition zone. The buttering layer has an austenitic structure with dendrite phase solidification, as shown in fig. xx. Buttering method is used for preventing carbon migration from the martensitic steel to austenitic steel and preventing creating hard carburized zone and carbon diffusion between materials. 7. Conclusion and future research Welding of X10CrMoVNb9-1 steel without PWHT remains a significant challenge due to the formation of brittle martensitic microstructures. Further research is needed to develop standardized procedures for this alternative method, ensuring the long-term reliability of X10CrMoVNb9-1 welds in high-temperature applications. The cold repair of