Residual stress distribution in Ni-based superalloy turbine discs during fabrication evaluated by neutron/X-ray diffraction measurement and thermomechanical simulation

Abstract

Residual stress distribution induced by multistep fabrication processes is of great significance in reliable design of critical engineering components, such as powder metallurgy Ni-based superalloy turbine discs. By using neutron diffraction and 2D-detector X-ray diffraction, the through-thickness residual stress distribution was determined in fabricated turbine discs via isothermal forging, solution treatment and aging treatment. The experimental results demonstrated that residual stress exhibited typical thermal stress distribution while plastic deformation-induced surface stress was relieved surprisingly after solution treatment. After aging treatment, the reduction of matrix supersaturation after long-time diffusion contributed to increase of compressive radial stress in the rim of disc. By introducing temperature-dependent supplementary phase transformation latent heat into the thermo-mechanical model, overall residual stress distribution after solution treatment was simulated by the finite element method. Numerical simulated stress distribution is in agreement with the experimental results, with the deviation < 40 MPa. Keywords: Residual stress, Ni-based superalloy, Neutron diffraction, 2D X-ray diffraction, Thermo-mechanical modeling