Predicting and Managing Heat Treatment Related Residual Stresses within Superalloy Forgings

The residual stresses developed during heat treatment of superalloy forgings result in a number of potential problems during subsequent manufacturing. They may lead to distortion of the forging which results in extra material being needed to ensure a part may be manufactured from it. The residual stress pattern may also lead to issues in machining the final component from the forging (the part moving during machining as the stresses attain a new equilibrium as material is removed).

A brief history of the numerical calculation of residual stresses during heat treatment (data needed and validation) is presented together with some examples of typical results obtained.  The paper also gives examples where modifications to the manufacturing process have resulting in alleviating the problems.   Finally the paper discusses more recent developments where computer models, together with more versatile production equipment, have been adopted to control the magnitude and pattern of residual stresses developed in a forging.