A workflow for designing contoured axisymmetric nozzles for enhancing additively manufactured cold spray deposits

One of the essential requirements in Cold Spray Additive Manufacturing (CSAM) is the control over the profile of the deposited materials. This paper introduces a workflow for designing contoured axisymmetric nozzles, which aims to improve on the metal particle delivery and the deposit profile of current commercial cold spray nozzles. The workflow uses two aerospace design codes based on the Method of Characteristics (MOC). By using coupled Eulerian-Lagrangian Computational Fluid Dynamics (CFD) simulations, the performance of a current commercial cold spray nozzle is compared with that of a redesigned nozzle. The new nozzle is obtained by performing a multi-objective optimization of the nozzle inner wall profile. This is done by varying the nozzle inlet convergent angle, the throat radius of curvature, and the inflection angle in the divergent section. The design performance is then assessed by evaluating a penalty function for each nozzle shape. The penalty function combines some of the most desirable characteristics in CSAM, namely a high particle impact velocity, a good spatial uniformity in this velocity and a good uniformity of the radial distribution of the particles. The numerical predictions show that the optimized nozzle shape delivers a more radially uniform deposit. A higher particle velocity is obtained at the same operating conditions/costs used by the industry standard nozzle. This study suggests that this integrated, multi-objective, parametric design approach can be built up in complexity to further improve the deposition performance of cold spray nozzles in additive manufacturing.