Mechanical characterization of P91 welded plate

Modified 9%Cr-1%Mo steel, designated as P91, is widely used in the construction of power plants and other sectors involving temperatures higher than 500oC. It normally transforms completely to martensite during air cooling. This means that issues related to the handling of weldment during welding operations, and between the completion of welding and post weld heat treatments are important concerns. Although the creep strength is the prime consideration, mechanical properties like tensile strength and hardness are also important since they can indicate the creep property from them. In this work TIG welded P91 plates were produced and test samples were extracted. The aim of this thesis is to characterize the welded plate by making mechanical tests on samples taken from the base metal and welded portion. The tests include hardness test, ambient and high temperature tensile tests, and microstructure investigation. High hardness was registered in the fusion zone, with decrement in the heat affected zone. The yield and ultimate stress of base metal and weld metal was found to be similar with slight difference in area reduction, but visible variation in percentage elongation in which the base metal had higher values the values of ultimate and yield stress have also showed low values at high temperature than the ambient. From the creep test carried out at 600 and 575 oC for both the BM and WM show that high temperature and welding increase the creep rate in the secondary zone.