Isothermal Fatigue Characterization of P91 Steel Under Load Control

P91 steels are widely used in power plants. They were developed in a context of increasing process temperatures to increase efficiency and reduce CO2 emissions into the atmosphere. In this sense, the energy industry aims to increase its efficiency and process control, for which temperature control is essential and welding thermocouples in P91 steel pipes may be necessary. In this context, this study aims to evaluate, in a preliminary way, the influence of welding thermocouples in P91 steel specimens subjected to fatigue testing. The results showed that in general there is a decrease in fatigue life, more prominent for 90 and 80% of the load. In addition, the insertion of defects such as welding points increases the probability of the initiation of fatigue cracks in the welded areas due to loss of properties. From 70% of the load onwards, infinite fatigue life was achieved for the welded and as suplied cases, and in both conditions the same fracture shape was obtained, observed macroscopically.