Structure and properties of the heat-affected zone of duplex steels welded joints

Influence of the secondary austenite γ2-precipitation in a heat-affected zone of welded joints of duplex steels, on hardness and corrosion resistance, have been analysed. The secondary austenite was created as a product of ferrite decomposition α → γ2 as an effect of the welding thermal cycle and an aging following the welding process. Correlation of the thermal cycle, γ2-phase morphology, kind of precipitations and hardness, as well as a corrosion resistance were described. Thermal cycle has a significant influence on the transformation α → γ2, and morphology of the created γ2-phases. The main mechanism of the secondary austenite creation is the diffusive transformation, as a result of which the Widmanstätten structure is formed. The increase of the γ2-phase quantity in the tested steel heat-affected zone causes an essential influence of the joint hardness and corrosion resistance.