Dependence of Bonding Mechanisms of Cold Sprayed Coatings on Strain-Rate-Induced Non-Equilibrium Phase Transformation

Strain-rate-induced amorphization at the impact interface of Ni-Cu was observed in a cold spray process by high-resolution transmission electron microscopy. Based on finite element analysis for the evolution of impact temperature and strain, strain-rate-induced phase transformation of dynamic amorphization, dynamic recrystallization, and oriented crystallization from the prior-formed amorphous were considered the possible bonding mechanism of cold spray coatings. Besides, the disordered structure within the central strain region may result from the strain-induced melting from jetting with the subsequent fast quenching, which improves the bonding and deposition of cold sprayed coatings.