Cold spray deposition of thermoplastic powder

The cold spray deposition of polyolefin powder has been investigated, at substantially lower velocities (up to ∼ 135 m s− 1) than those used in the cold gas dynamic spray (CGDS) process for metals. The particles were accelerated at room temperature in air through a cylindrical nozzle, and were deposited on to polyethylene and aluminium substrates. Fully-dense deposits were formed at temperatures substantially below the melting point of the polymer, and the critical impact velocity for deposit growth was ∼ 100 m s− 1. Melting of the polymer particles did not occur. The influences of polymer particle size, impact velocity, nozzle stand-off distance and substrate material on the deposition process were studied. Although deposition occurred readily on to polyethylene substrates at room temperature, it was initiated on aluminium substrates only after a thin film of melted polymer had been formed to act as a bonding layer. The deposition efficiency was much lower than the values typically seen in CGDS of metals.