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P92 steel is a modern martensitic heat-resistant steel currently used for seamless products for pressure equipment operating in supercritical operating parameters. The paper presents the results of a study on the strength properties and structure of a P92 steel welded joint used for pressure components of power units. The paper presents an assessment of the suitability for further operation of both the parent material and a circumferential similar welded joint of finished products in the form of P92 steel pipes after annealing for 3000 hours at 600 and 650°C. Annealing at 650°C results in faster increase in the size of the precipitates and their coagulation along grain boundaries of former austenite and martensite laths. The changes in mechanical properties were compared in relation to the state of the structure of the parent material and the material of the welded joint. Quantitative analysis of M23C6 precipitates was also carried out. [ABSTRACT FROM AUTHOR]

The paper shows the degradation process of the modern austenitic Super 304H (X10CrNiCuNb18-9-3) steel which was subjected to long-term ageing for up to 50 000 h at 650 and 700°C. The investigations include microstructure examination (SEM), identification and analysis of the precipitation process, and mechanical properties tests. The Super 304H steel has a structure characteristic of austenitic steels with visible annealing twins and single primary NbX precipitates. Long-term ageing in steel leads to numerous precipitation processes of M23C6, MX carbides, s phase, Z phase, and e-Cu phase. Precipitation processes lead to a decrease in plastic properties and impact energy as well as alloy over ageing. Yield strength and tensile strength values after 50 000 h of ageing were similar to those as delivered. The yield and tensile strength value strongly depend on the applied ageing temperature. [ABSTRACT FROM AUTHOR]