Strain-Age Cracking after Postweld Heat Treatments in Inconel 738 Superalloy

Abstract

The effect of postweld heat treatment (PWHT) conditions after TIG welding for repairs of fractured turbine blades made of cast nickel-based superalloy, Inconel 738, have been studied. The PWHT was employed to provide more homogeneous microstructural characteristics in a welded zone. It was found that the PWHT with high solutioning temperature of 1478 K resulted in hot cracking in base metal near welding zones, even it provided the most homogeneous microstructural characteristics in welding specimens. The microstructure near hot cracking consists of very fine particles in heat-affected zone (HAZ) with high area fraction.