TY - JOUR N2 - S304H steel is used in the construction of pressure components of boilers with supercritical operating parameters. The paper presents the results of research on the microstructure following ageing for 30,000 hours at 650 and 700°C. Microstructure examination was performed using scanning and transmission electron microscopy. The precipitates were identified using transmission electron microscopy. The paper analyses the precipitation process and its dynamics depending on the temperature and ageing time in detail. MX carbonitrides and the ε_Cu phase were proved to be the most stable phase, regardless of the test temperature. It was also showed that the M₂₃C₆ carbide precipitates in the tested steel and the intermetallic sigma phase (σ) may play a significant role in the loss of durability of the tested steel. This is related to their significant increase due to the influence of elevated temperature, and their coagulation and coalescence dynamics strongly depend on the ageing/operating temperature level. The qualitative and quantitative identification of the secondary phase precipitation processes described in the study is important in the analysis of the loss of durability of the tested steel under creep conditions. L1 - http://www.journals.pan.pl/Content/119845/PDF/05_02196_Bpast.No.69(5)_drukM.pdf L2 - http://www.journals.pan.pl/Content/119845 PY - 2021 IS - 5 EP - e137520 DO - 10.24425/bpasts.2021.137520 KW - S304H steel KW - microstructure KW - precipitates KW - ageing KW - loss of durability A1 - Zieliński, Adam A1 - Wersta, Robert A1 - Sroka, Marek VL - 69 DA - 01.06.2021 T1 - Analysis of the precipitation process of secondary phases after long-term ageing of the S304H steel SP - e137520 UR - http://www.journals.pan.pl/dlibra/publication/edition/119845 T2 - Bulletin of the Polish Academy of Sciences Technical Sciences ER -