Effect of Particle and Substrate Pre-heating on the Oxide Layer and Material Jet Formation in Solid-State Spray Deposition: A Numerical Study

In a solid-state deposition technique such as cold spray (CS) or high-velocity air-fuel (HVAF), particle and substrate initial conditions play a crucial role in particle deformation and its adhesion strength to the substrate. In these thermal spray techniques, the deposited particle and the substrate are required to deform plastically; hence, both components are usually metallic. An oxide layer at the surface of these metallic components may avoid producing a metallurgical bonding and strong adhesion between them. To better understand the effect of particle and substrate initial conditions, e.g., particle velocity, particle temperature, and substrate temperature, on the formation of metallurgical bonding, it is necessary to examine particle and substrate oxide layer failure. In this work, the effect of a 20 mu m Ti-6Al-4V particle and a Ti-6Al-4V substrate initial conditions on the failure of their oxide layer during impact has been studied. The results show that the presence of an oxide layer increases the required critical velocity for particle adhesion on the substrate. Furthermore, regardless of the chosen initial conditions, the particle oxide layer would fail in the adiabatic shear instability region because of the severe deformation that the particle experiences upon impact. This study shows that a stronger bonding between the deposited particle and the substrate can be achieved by increasing the particle velocity and substrate temperature, as they increase the extent of the failed oxide layer region of the substrate. Rising particle temperature increases particle deformation and has no significant effect on the adhesion between the particle and substrate.

Automated summary

In solid-state deposition techniques, the initial conditions of particles and substrates are crucial for particle deformation and adhesion strength to the substrate. The presence of an oxide layer increases the required critical velocity for particle adhesion, while particle temperature has no significant effect on adhesion between the particle and substrate.