Distortion prediction and compensation in direct laser deposition of large axisymmetric Ti-6Al-4V part

Abstract

A Ti-6Al-4V alloy aircraft engine part consisting of a cylinder (inner radius 977 mm, height 250 mm and 7.5 mm wall thickness) and two flanges (10.5 and 13.5 mm thick) was manufactured by direct laser deposition technology. A two-dimensional thermomechanical model was developed to simulate distortion of large axisymmetric parts during direct laser deposition. As it was established the shape and dimensions of the finished part, simulated using the original CAD model, have unacceptable deviations from the required parameters. A significant correction of the model is necessary to ensure the required accuracy. It was found that for complete compensation of deformations, an initial geometry should be pre-distorted according to the inverted distortions predicted by the FE simulation. To prevent fracture of the build-up, an 8 mm thick flexible substrate was used. The DLD process stability was ensured by taking into account spatial position of the deposited part in the motion path of the processing head. The simulated shape and size of the finished part satisfactory agrees with the experimentally obtained.