Residual stress effects during additive manufacturing of reinforced thin nickel–chromium plates

Additive manufacturing (AM) is a powerful technique for producing metallic components with complex geometry relatively quickly, cheaply and directly from digital representations; however, residual stresses induced during manufacturing can result in distortions of components and reductions in mechanical performance, especially in parts that lack rotational symmetry and, or have cross sections with large aspect ratios. Geometrically reinforced thin plates have been built in nickel–chromium alloy using laser-powder bed fusion (L-PBF) and their shapes measured using stereoscopic digital image correlation before and after release from the base-plate of the AM machine. The results show that residual stresses cause potentially severe out-of-plane deformation that can be alleviated using either an enveloping support structure, which increased the build time substantially, was difficult to remove and wasted material, or using buttress supports to the reinforced edges of the thin plate. The buttresses were quick to build and remove, minimised waste but needed careful design. Plates built in a landscape orientation required out-of-plane buttresses while those built in a portrait orientation required both in-plane and out-of-plane buttresses. In both cases, out-of-plane deformation increased on release from the baseplate but this was mitigated by incremental release which resulted in out-of-plane deformations of less than 5% of the in-plane dimensions.