The effect of the solution treatment onto the microstructure and mechanical properties of MAG pulsed welded joints from X2CrNiMoN22-5-3 Duplex stainless steels

The metallurgical behaviour by Duplex stainless steels welding is affected by reducing the austenite proportion in weld and in the area adjacent to the fusion line of the molten metal bath and also by the precipitation of nitrides Cr2N, carbides M23C6 and intermetallic phases, sigma, , Laves. The modalities for obtaining a quantitative ratio of the two phases (Austenite/Ferrite) close to that of the base metal (approximate to 50% Austenite and 50% Ferrite) aims to adjust the chemical composition of the weld by selecting a filler material with a higher nickel content (the element which beside nitrogen promotes the austenite formation), the heat cycle control of the welding process and the application of a post-welding solution treatment. The present paper explores the effect of such heat treatment on balance restoring between austenite and ferrite and the reduction of the alloying elements segregation phenomena. By optical and scanning electron microscopy examinations and also X-ray diffraction analyses the microstructural changes induced by the applied treatment are highlighted and by impact toughness and static tensile tests is demonstrated the positive effect of the heat treatment onto the ensuring of the welded joints quality.