Abstract
Inconel alloy 740, a precipitation-hardenable nickel-chromium-cobalt alloy with niobium addition, has emerged as a leading candidate material for ultra-supercritical (USC) boilers due to its superior stress rupture strength and corrosion resistance at operating temperatures near 760°C. While derived from Nimonic alloy 263, alloy 740's unique chemistry necessitates comprehensive weldability studies to address potential challenges including heat-affected zone liquation cracking, ductility-dip cracking, and post-weld heat treatment cracking. This ongoing investigation examines the alloy's weldability characteristics through material characterization studies comparing its cracking sensitivity to established aerospace alloys like Waspalloy and Inconel alloy 718. The research applies aerospace industry expertise to boiler applications requiring sections up to three inches thick, with gas tungsten arc welding and pulsed gas metal arc welding identified as the most promising processes for producing sound, crack-free welds.
