Residual Stresses Around Welds in Nickel-based Superalloys

Abstract

Welding of nickel-based superalloys is employed in the manufacture of many important components of the jet engine, such as combustor casings, compressor disc assemblies, etc. Welds induce microstructural modification in the weld seam and the heat affected zone (HAZ) which generally reduce the fatigue resistance compared to that of the parent metal. Welds also generate significant residual stresses, both locally due to combination of solidification shrinkage and high temperature plastic deformation, and also globally through the general tensioning of the structure. Diffraction of high energy synchrotron X-rays is very well suited to the task of accurate non-destructive evaluation of residual stresses near welds in thin walled components assembled by welding nickel superalloys. Residual stresses induced by linear and annular welds produced in test pieces made from C263 and IN718 nickel based alloys under different conditions are evaluated, and the effects of various heat treatments on stress state are discussed.