This work addresses some of the challenges associated with depositing copper on PEEK by cold spraying. Getting copper powder to adhere to the PEEK substrate is not difficult at first, but deposition efficiency falls rapidly during coating build-up. Without heating the propellant gas, a copper coating will not form, even at the highest gas pressures. Increasing prechamber pressure is necessary, but requires an increase in gas temperature to 400°C to reach a deposition efficiency of 70%. Subjecting PEEK to such heat causes delamination issues that offset the deposition efficiency gained.

In this study, icephobic polymer coatings were produced by flame spraying using different process parameters. Process optimization for low-density polyethylene (LDPE) coatings was achieved through design of experiments. The most icephobic coating was produced at a traverse speed of 900 mm/sec and a spraying distance of 250 mm. Although surface roughness affected ice adhesion, thermal effects proved to be the main factor influencing the performance of the coating. The higher the processing temperature, the smoother the surface and the greater the polymer degradation. It is also shown that coating degradation can be caused during post heating steps with similar consequences in the ice-shedding performance of the LDPE coatings.

The ongoing development of new HVOF spray guns for internal diameters is driving demand for finer spray powders. Fine spray powders (< 20 µm) are necessary to achieve short spray distances, but they also create new challenges. The first steps in the thermal spray process chain are powder preparation and feeding. If these steps are not stable, no sufficient coating quality can be obtained. This present work compares volumetric and fluidization powder feeding methods and investigates the feeding behavior of agglomerated and sintered WC-Co(Cr) powders with particle fractions of -5+15 µm, -20+5 µm, and -10+2 µm. Particle size fraction was measured ex situ by laser diffraction and particle outflow from the injectors was recorded in-situ by means of particle image velocimetry.

Single component tin coatings have been successfully cold-sprayed onto carbon fiber reinforced polymers. Coatings with mixed metal powders have also been sprayed to improve conductivity for lightning strike protection purposes. Test results indicate a noticeable improvement in deposition efficiency with the addition of a secondary metallic powder. This study examines the effect of aluminum powder additions in tin coatings. Following cold spraying of various Sn-Al mixtures over a wide range of gas pressures, unusual coating morphologies were observed. The study of these morphologies reveals two distinct deposition phases depending on spray pressure. The presence of submicron particles also supports the occurrence of a powder melting phenomenon during the spraying process.

Tin coatings have been successfully applied to polymeric substrates by means of cold spraying. In this work, three low melting point powders, including Sn, Sn-Zn, and Sn-Bi, are cold sprayed onto various polymeric substrates and different combinations of gas temperature and pressure are assessed. Based on the results, the effect of melting points on the cold sprayability of feedstock powders is discussed.