Residual Stress Distributions in Cold-Sprayed Copper 3D-Printed Parts

Cold-spray additive manufacturing (CSAM) builds strong, dense metal parts from powder feedstock without melting and offers potential advantages over alternatives such as casting, liquid phase sintering, laser or e-beam melting or welding. Considerable effort is required to relieve residual stresses that arise from melt/freeze cycling in these methods. While CSAM does not involve melting, it imposes high strain rates on the feedstock and stress anisotropies due to complex build paths. This project explores residual stress in two CSAM objects. The CSAM components were produced from 99% pure copper powder (D50 = 17 µm): (1) a cylinder (∅ = 15 mm, height = 100 mm, weight = 145 g) and (2) a funnel (upper outer ∅ = 60 mm, lower outer ∅ = 40 mm, wall thickness = 8 mm, weight = 547 g). The non-heat-treated components were strain-scanned using a residual stress neutron diffractometer. Maximum residual stresses in any direction were: tensile: 103 ± 16 MPa (cylinder) and 100 ± 23 MPa (funnel); compression: 58 ± 16 MPa (cylinder) and 123 ± 23 MPa (funnel). Compared to the literature, the tensile residual stresses measured in the CSAM components were lower than those measured in cast materials, laser or welding AM methods, and numerical modelling of cold-spray coatings, while within the wide range reported for measurements in cold-spray coatings. These comparatively low residual stresses suggest CSAM is a promising manufacturing method where high residual stresses are undesirable.