Forming property and broaching error prediction of a forged nickel-based superalloy turbine disc

In order to improve the forming quality and the reliability performance of the aeroengine turbine disc, the initial residual stress derived from the multi-stage forging process should be studied principally. Two different methods, the layer removal and the finite element method (FEM), were used to analyze the prevailing residual stress in the multi-stage forged GH4169 (similar to Inconel 718 alloy) nickel-based superalloy turbine disc. The measured stresses were used to validate the predicted stresses obtained from a thermal-mechanical coupled FE model of the forging process by using a combined two-dimensional (2D) and three-dimensional (3D) simulation technology. The test validated FE model would give a comprehensive and accurate description of the residual stress distribution in the forged turbine disc, which could be effectively served for the disc manufacturing process optimization. Especially for the turbine disc mortises, the FE residual stress model was used to predict the manufacturing tolerance under different broaching technologies. The initial forged residual stress in the turbine disc would be the critical factor for the advance of the difficult-to-deformation material manufacturing processes with high dimensional accuracy and reliability.