Microstructure characterization and hardness distribution of 13Cr4Ni multipass weld metal

• Effects of weld passes' thermal cycle on microstructure and hardness of adjacent weld beads in a 13Cr4Ni multipass joint
• Regions inside an as-welded bead of a 13Cr4Ni multipass weld
• Inhomogeneity inside a 13Cr4Ni multipass weld

Multipass welding is a common method for fabrication and repairs of large industrial steel parts. In the hydroelectric industry these parts are commonly made with 13Cr4Ni steels that present outstanding performances. In this research the microstructures and crystallographic textures of a multipass weld have been studied. The microstructure was found to be complex and heterogeneous, consisting of several regions affected by adjacent weld passes. The study showed that austenite parent grains modification happened in areas close to the subsequent weld passes. However, parallel and low angle interface laths were observed inside martensite sub-blocks over different regions. The hardness profile was explained by overlaying the simple three regions heat affected zone. In some regions a tempering heat treatment effect was observed while in some other regions a double-quenching has happened.