The paper deals with the possibility of using the SPT - (small punch test) method for evaluation of material properties of the individual areas of welded joints. The homogeneous and heterogeneous welds for USC power plants were assessed. The selected combination of welded joints made of austenitic creep resistant steels of the TP347 HFG, HR3C, Super304H and P92 grades in as-received state and after exposure in the real boiler conditions for one year were studied. The mechanical and fracture properties were assessed using small punch test of welds under investigation. The mechanical properties and fracture properties were studied using miniaturized tests, too. From the results it can be concluded that especially fracture properties were influenced significantly due to one-year exposure, which can be demonstrated on the Charpy impact tests, where the impact energy dropped down to only 1/3 of the original value.Keywords: Austenitic steels, small punch test (SPT), welded joints, sigma phase, mechanical and fracture properties
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