Cold Spray Additive Manufacturing of Polymers: Temperature Profiles Dictate Properties Upon Deposition

Abstract

The cold spray additive manufacturing process enables deposition of coatings and structures by impact bonding microparticles to surfaces through preheated, nozzle-accelerated gas flow. Most established models of gas-particle heat transfer in cold spray assume lumped thermal capacitance, which ignores particle temperature distributions and is typically valid for metals. However, recent advances in cold spray consider polymeric systems that differ categorically and considerably in thermophysical properties compared to metals. Particularly, the low Biot number (Bi) assumption may be invalid, impacting efficiency and quality of polymeric particle deposition. We describe herein a 1D transient gas-particle heat transfer model that simulates temperature profile evolution in a representative particle traveling through a cold spray nozzle. With this model, we simulated thermal histories of polymeric materials at realistic processing conditions. Polymer sprays with Bi consistently near 10 -1 or greater demonstrated thermal inhomogeneities, in some cases straddling the glass transition temperature. Thermal stratification provides insight into physical conditions of a particle before deposition, which can guide processing parameters to improve deposition efficiency and quality of polymer cold sprays.

Cold Spray Deposition of Nylon-6 on Glass Fiber-Reinforced Composites

“…1,2 In this process, a heated high-velocity gas stream accelerates micronsized particles through a nozzle, spraying them directly onto the surface of a stationary target substrate. 3,4 Upon impact, bonding between the substrate and particles forms primarily due to the occurrence of severe plastic deformation in the particle−substrate interface vicinity. 4 Cold spray offers certain advantages over other thermal spray processes (e.g., plasma or arc spraying) as less heat is required for the successful deposition of the particles.…”

“…3,4 Upon impact, bonding between the substrate and particles forms primarily due to the occurrence of severe plastic deformation in the particle−substrate interface vicinity. 4 Cold spray offers certain advantages over other thermal spray processes (e.g., plasma or arc spraying) as less heat is required for the successful deposition of the particles. 3,5 The use of less intense heating leads to reduced surface distortion, fewer defects, and lower residual thermal stresses.…”