Microstructure and mechanical properties of a modified P911-type steel weld joint

In the present work, the plates of P911-type steel were preheated to 250°C and welded using similar filler material with high boron and low nitrogen contents. Post-weld heat treatment was carried out at 760°C for 3 hours. Microhardness profile across the weld joint and tensile properties of the weld joint at temperatures up to 760°C were obtained. The joints were studied in detail by scanning and transmission electron microscopy. The weld zone is characterized by hardness of about 300 HV. At room temperature YS, UTS and δ were 470 MPa, 670 MPa and 13%, respectively. With an increase in test temperature to 760°C YS and UTS decreased to 130 MPa and 150 MPa respectively, and elongation increased to 18%. A decrease in dislocation density and subgrain growth was observed in the heat-affected zone after post-weld heat treatment. Obtained results can be used for the development of optimal welding conditions for advanced P911-type steels.