Residual stresses and distortion in the patterned printing of titanium and nickel alloys

Since the deposition patterns affect the stresses and distortions, we examined their effects on multi-layer wire arc additive manufacturing (WAAM) of Ti-6Al-4V and Inconel 718 components experimentally and theoretically. We measured residual stresses by hole drilling method in three identical components printed using different deposition patterns. In order to understand the origin and the temporal evolution of residual stresses and distortion, we used a well-tested thermo-mechanical model after validating the computed results with experimental data for different deposition patterns. Distortions were also examined based on non-dimensional analysis. We show that printing with short track lengths can minimize residual stresses and distortion among the three patterns investigated for both alloys. Both Ti-6Al-4V and Inconel 718 had similar fusion zone shape and size and were equally susceptible to deformation and warping, although Ti-6Al-4V was relatively less vulnerable to delamination due to its higher yield strength. A dimensionless strain parameter accurately predicted the effects of WAAM parameters on distortion and this approach is especially useful when the detailed thermo-mechanical calculations cannot be undertaken.