Executive Summary : | Advanced ultra-supercritical (AUsC) thermal power units are being developed by many countries to achieve high energy efficiency and minimal carbon footprints. These units can reduce CO2 emissions by 22% compared to conventional power units. The first UsC unit was constructed in the 1960s at 600°C and 34.5 MPa, and after successful design and operation of 600°C UsC power plants, AUsC units were developed in 2001. The AUsC technology increases temperatures and pressures by 100°C and 10 MPa compared to 600°C UsC technology. This has led to the development of various superalloys, such as Alloy 617, Inconel 625, Inconel 740H, Haynes 263, and Haynes 282, which are suggested for use in high-temperature sections of superheaters and reheaters operating under AUsC boilers. However, these superalloys are more expensive than conventional heat-resistant steels due to their high alloying elements. To ensure safe operation of AUsC power units, proper welding techniques and weld parameters are essential. Tungsten Inert Gas (TIG) welding is popular for preparing critical and robust dissimilar weld joints, but its successor, Activated-Tungsten Inert Gas (A-TIG), is being explored for weld characteristics juxtaposition. The aim of this work is to develop a suitable flux composition for the A-TIG process to obtain sound quality weld joints of heat-resistant ferritic/martensitic P91 steel and Inconel 617 alloy for AUsC application. |