Microstructural and mechanical properties assessment of the P91 A-TIG weld joints

In the current work, the effects of CeO2 and MoO3 based activating flux on heat input, weld bead geometry, and angular distortion during single pass A-TIG welding of the P91 steel were evaluated and compared with the conventional TIG welding. The A-TIG weldments developed using CeO2 and MoO3 based activating flux were also undergone for microstructure, microhardness, tensile test, and Charpy impact test study. It was observed that, the heat input increases in presence of activating fluxes at same welding input variables namely welding current, welding speed and arc length. An increase of 200% and 300% in joint penetration was obtained with CeO2 based flux and MoO3 based flux, respectively as compared to the conventional TIG weldments. Microstructure study reveals the presence of lath martensite, prior austenite grain boundaries along with MX (M: Nb, V, and X: C, N) and M23C6 (M: Fe, Mo, Mn, and Cr) type of precipitates in different zones of the weldments. Tensile strength of the A-TIG weldments was found better than that of the base metal. However, the Impact toughness of the A-TIG weldments was found to very low than the base metal.