| Abstract Scope |
Particle velocity is a critical parameter in cold spray because sufficient impact velocity is required to induce severe plastic deformation, interparticle bonding, and deposit formation. Nozzle geometry influences gas expansion, flow acceleration, shock structure, particle acceleration, and the resulting deposit microstructure. However, the relationship between nozzle geometry, particle-velocity evolution, gas pressure, temperature and microstructural development remains insufficiently understood.
This study investigates different nozzle configurations under equivalent cold spray conditions using compressible-flow CFD coupled with discrete particle tracking. The model resolves gas flow, Mach number, pressure evolution, shock structures, particle trajectories, and velocity histories. Experimental in-flight particle-velocity measurements using powders with different particle-size distributions validate the simulations. Deposits produced with each nozzle are characterized for particle deformation, interparticle bonding, porosity, and interfacial defects. The results establish correlations between nozzle geometry, in-flight particle velocity, and deposit microstructure, providing a basis for nozzle designs that improve deposition-relevant velocity characteristics and deposit quality. |