Improving mechanical properties of P91 and IN617 dissimilar weld joints for advanced ultra super critical power plants by buttering technique

Abstract

• Enhancement of mechanical properties using buttering layer for dissimilar weld. • Buttering helps in achieving favorable ductility for dissimilar welds. • With buttering creep rupture life of dissimilar welds has increased. • Buttered dissimilar welds can be implemented for very high-temperature boilers. To improve the mechanical properties of ferritic steel and nickel superalloy, while maintaining economic symmetry, this investigation is performed on fabricating dissimilar metal welds for advanced ultra-supercritical (AUSC) boilers, with a buttering technique. The present work compares a dissimilar weld of IN617 alloy and P91 steel with and without buttering by multipass gas tungsten arc welding for mechanical properties variations, creep strength at elevated temperature, and microstructural evolution. Thin layers of buttering material are applied at the ferritic end, followed by the closure weld consisting of welding a second member to a butter layered component. Further, significant improvement in mechanical properties (tensile strength, toughness, and hardness) and creep rupture life (though the failure remains ductile characterized by dimples variations) 2 to 3 times longer has been found with buttering in contrast with no buttering.