Integrated model for tracking defects through full manufacturing route of aerospace discs

Abstract

Process models simulating the various stages of gas turbine disc manufacture have been integrated to simulate defect tracking throughout the entire manufacturing route: vacuum induction melting, vacuum arc remelting (VAR), homogenisation heat treatment, cogging, forging, final heat treatment and machining. An integrated complete manufacturing route model allows intrinsic or extrinsic defects entrained within the material during the initial VAR stage to be tracked through the subsequent processes. This enables determination of the motion of these defects during hot deformation stages as well as calculation of whether they might be removed during machining. If they remain in the final component, they may potentially serve as initiation sites for in service failure. The model was applied to a generic disc geometry and it was found that intrinsic defects formed (such as freckles and discrete white spots) during VAR at mid-radius spots are undesirable as they have a high probability of remaining in the final disc. Inclusions in the central region or near edge, such as solidification or dendritic white spot and extrinsic particles, are frequently removed during final machining. Further, it was demonstrated that the technique can also be used for diagnosing the origins of defects found in the final machined disc by tracking their motion in reverse to obtain their initial location in the upstream processes, thus providing a tool to help optimise quality control through process design.