Development of a Deposition Strategy in Cold Spray for Additive Manufacturing to Minimize Residual Stresses

Cold Spray (CS) is a rapidly developing metal deposition technology, which allows for the formation of coating layers in a melt-free manner and is starting to replace existing technologies at industrial level. New developments in the field of CS as well as optimization of spraying strategy permit to elaborate freeform 3D objects with reasonable precision. Residual stress is among the most important factors affecting coating integrity in fact they can lead to peeling and/or delamination of coatings. In this study two different types of simulation were performed: at the microscale, using ANSYS-AUTODYN, a high impact simulation in order to study the mechanism of formation of residual stress in the cold-sprayed deposited particle; and at the macroscale a static structural simulation based on Tsui and Clyne's progressive deposition model in order to investigate a possible interaction between different layers and developing a deposition strategy. For the first time, in this work, a parametric study of the single impact particle to study the residual stress was proposed finding that impact velocity; incident angle of impact and density and the yield stress for the materials involved in the deposition have a strong influence in the residual stress formation. Furthermore, at a macroscopic scale, a deposition strategy that minimises residual stress was identified. In fact, it was found that the deposition of successive layers with a perpendicular relative orientation leads to a final product with lower residual stress.