Evaluation reveals robust tensile strength in sanicro 25 weld joint, suggesting excellent mechanical stability.
Sanicro 25 stainless steel is a candidate structural material for boiler tubes in Indian Advanced Ultra Supercritical (AUSC) coal-fired thermal power plants with design steam parameters of 983/993 K and 310 bar. The aim of the present study is to develop the Orbital TIG welding procedure, evaluation of microstructure and properties of Sanicro 25 tube base metal and weld joint. For this, Orbital TIG welding (5 G position) was carried out using J-groove weld edge preparation and ERNiCrCoMo-1 filler wire. Welding parameters were optimized to achieve the uniform weld root penetration and side wall fusion. The cross weld average tensile strength of 798 MPa is significantly higher than the minimum tensile strength requirement of 655 MPa for base metal. The weld joint also passed side bend test. Sanicro 25 base metal showed equiaxed grain structure with bimodal grain size distribution with an average grain size of 50 μm. Nb& Cr-rich primary precipitates are observed in the base metal in sizes ranging from 0.2 to 4 μm. The weld metal showed elongated grains with inter-dendritic Mo & Cr-rich precipitates. Impression creep tests at 973 K showed that the weld metal exhibits superior creep resistance compared to the base metal.
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Unikela et al. (2025) studied this question.
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