Deposition of thermoplastic polymers by HVOF

Thermoplastic coatings are of interest in terms of corrosion protection, insulation or as functionalized coatings. Thermal spraying of polymers requires precise temperature setup of the process in order to avoid polymer degradation while obtaining adequate mechanical performance of the coating through sufficient sintering of the polymer. Heat transfer into the polymer powder is critical due to the low thermal conductivity of thermoplastics. Polyurethanes were thermally sprayed using HVOF technology. The window of deposition was investigated changing stoichiometry, total gas mass flow and standoff distance. The dependence of the process parameters on coating microstructure and mechanical properties of the polymer was investigated with particular respect to process temperatures. Additionally, the influence of subsequent process steps like thermal treatment on sintering of the polymer was investigated. The work aims at obtaining robust sintering of the particles and hence mechanical properties close to the theoretical values of the polymer used.