Interface melding in cold spray titanium particle impact

A focused ion beam (FIB) was used to characterize deformation and bonding behavior of titanium particles, cold sprayed onto a titanium surface. By milling away half of each particle a cross-section was obtained, revealing the particle-substrate interface. It was found that in some sections, voids lined the interface due to mismatch in particle- and substrate-surface topologies. In other places, the interface could not be discerned due to closure of the voids. It is shown that this effect was related to adiabatic shear instability, which caused violent jetting, ejection of molten material from the particle, and thermal softening of the interfacial layers. Deformation characteristics and variation in splat profiles due to microstructural influences, and the effect of particle size are also discussed.