Towards Strength-Ductility Synergy in Cold Spray for Manufacturing and Repair Application: A Review

Cold spray is a solid-state additive manufacturing technology and has significant potential in component fabrication and structural repair. However, the unfavourable strength-ductility synergy in cold spray due to the high work hardening, porosity and insufficient bonding strength makes it an obstacle for real application. In recent years, several methods have been proposed to improve the quality of the cold-sprayed deposits, and to achieve a balance between strength and ductility. According to the mechanism of how these methods work to enhance metallurgical bonding, decrease porosity and reduce dislocation densities, they can be divided into four groups: (i) thermal methods, (ii) mechanical methods, (iii) thermal-mechanical methods and (iv) optimisation of microstructure morphology. A comprehensive review of the strengthening mechanism, microstructure and mechanical properties of cold-sprayed deposits by these methods is conducted. The challenges towards strength-ductility synergy of cold-sprayed deposits are summarised. The possible research directions based on authors' research experience are also proposed. This review article aims to help researchers and engineers understand the strengths and weaknesses of existing methods and provide pointers to develop new technologies that are easily adopted to improve the strength-ductility synergy of cold-sprayed deposits for real application.