Residual stresses induced by Inconel 718 cold gas repair spray of large cavities — On the influence of the sample geometry

Following previous studies regarding the suitability of cold gas spray (CGS) for repairing large cavities in flat Inconel 718 components, circular specimen geometries were produced which contained tapered cavities with a depth of 4 mm. Two sets of process parameters, a hot and a cold parameter set, were used to fill the cavities with similar material by employing CGS. To evaluate the local residual stress state in the as-sprayed condition, non-destructive high-resolution neutron diffraction experiments were performed on the SALSA instrument at the Institut Laue-Langevin (ILL). 2D mappings of residual stress distributions were determined over the cross-sectional area in the centre of the specimens. Additionally, complementary laboratory residual stress analyses were carried out. The results of residual stress analyses indicate compressive residual stresses within the repaired zone, which are balanced by tensile residual stresses in the substrate adjacent to the repair site. Supplementary metallographic investigations show a good bonding between the repair filling and the substrate as well as strongly deformed particles within the repaired region. The latter indicates significant work hardening occurring during CGS. This is further supported by the increased widths of the diffraction lines recorded by neutron diffraction analyses and micro hardness distributions.