The Effect of Specimen Size for the P91 Steel at Elevated and High Temperatures

The contribution aims to evaluate fracture toughness of the P91 steel in the ductile regime. This steel is broadly used for applications for pressure vessels and piping systems. The J–R curves were obtained using 1T, 0.5T and 0.25T CT specimens at 23 °C and using 0.5T and 0.25T CT specimens up to 600 °C. The energy normalization method for the J–R curve determination according to the ASTM E1820 was used. The resistance to crack propagation shows temperature dependence and the dynamic strain ageing effect with minimum values at 400 °C. Both specimen sizes 0.5T and 0.25T give a similar trend of the temperature dependence of fracture toughness. However, the size effect is observed as fracture toughness decreases with the specimen size. The results obtained are compared with the results of other authors pointing the specimen size effect and the temperature dependence of the steel.