Abstract Scope |
This work proposes an alternative electrode coating composition and presents a systematic method for designing and developing SMAW electrodes in a laboratory. A high basicity index CaO-CaF2-TiO2-SiO2 based coating has been formulated using extreme vertices design approach for welding super duplex steel offshore structures. Twenty-one coating compositions have been designed and characterized for different thermophysical, physicochemical, structural and wettability properties to assess their suitability. The investigated coating properties include density, enthalpy, specific heat, thermal conductivity, diffusivity, thermal stability, bond length analysis, structural phases, contact angle, spreadability, and surface tension upon melting. Adopting the sustainable engineering approach, the commercial ferro-alloy powders have been replaced with iron ore mineral waste red ochre as a constituent of the coating composition. The developed coatings were further extruded on 309L austenitic stainless steel core wire. The extruded electrodes were then used to make multi-pass beads on a super duplex stainless steel substrate. The beads were qualitatively and quantitatively analyzed to select the two best coating compositions out of 21 from the design matrix. The chosen electrodes were then used to weld a dissimilar joint between super duplex stainless steel and pipeline steel. Another weld between the same steels was fabricated using commercially available 309L coated electrodes. A comparative analysis of weld’s mechanical and metallurgical properties clearly indicates that laboratory-developed electrodes were found to perform suitably and comparatively to the commercially available electrodes. For some of the properties, the laboratory developed electrode fair better. |