Numerical simulation of cold-sprayed hydroxyapatite coating on 316L stainless steel

This study numerically investigates the deposition behavior of cold-sprayed hydroxyapatite (HA) coatings on a 316L stainless steel substrate. The velocity of HA particles sprayed using a de Laval nozzle was estimated using the discrete phase mode (DPM) model in FLUENT. Particle retention was subsequently analyzed using the Coupled Eulerian Lagrangian (CEL) and Smoothed Particle Hydrodynamics (SPH) models. The critical or threshold particle velocity was determined to be 577 m/s. Higher particle retentions were observed for impacted velocities closer to this threshold. Various morphologies of the splat were observed depending on the impact velocity, ranging from cap-shaped to ring-like structures. At impact velocities exceeding 677 m/s, the central part of the splat detached due to high spring back force, leaving behind ring-like particle remnants on the substrate. Moreover, beyond this velocity, stripes surrounding the splat diameter and grooves around the cap were observed due to material fragmentation. The study emphasizes the significant role of particle velocity and mechanical interlocking in bonding and retaining HA coatings on the metal substrate, distinct from adiabatic shear instability prevalent in metal-on-metal coatings.