Fluorinated polymer coatings are potential candidates for ice protection systems. The current work aims to develop such coatings using cold spray as a production method. A computational approach is used to design a new cold spray nozzle for the efficient deposition of adhesive perfluoroalkoxy alkane. The icephobicity of as-sprayed coatings are evaluated using three-fold characterization: surface’s wetting behavior, time-lapse study of water droplets freezing, and ice adhesion at both macro and microscopic levels. While the as-sprayed coatings exhibited sought superhydrophobic properties, their behavior changed when exposed to frost formation resulting in degraded wetting behaviors and much larger ice adhesion strength. This demonstrates the importance of frost formation when studying icephobic coatings.

Segregating the convoluted effects of particle size, impact temperature and velocity on deposition behavior and adhesion is of utmost interest to the cold spray field. The current study aims to associate the particle impact behavior and adhesion to its in-flight characteristics by studying and decoupling the influence of particle size, temperature and velocity for single particle impacts and full coatings. Experimental results reveal that in-situ peening processes contribute to the adhesion at low impact temperature while particle velocity controls the adhesion/cohesion at increased particle impact temperatures. The benefits of both bonding mechanisms are discussed in terms of measured adhesion/cohesion, bend-to-break fracture surfaces, pseudoplasticity, deposition efficiency and critical velocity. Computational fluid dynamics (CFD) results provide individual particle trajectory, size, temperature and velocity, of successfully deposited particles, which have led to the observed signs of metallurgical bonding.

This study demonstrates a new approach for producing thick copper coatings on steel by cold spraying via nitrogen gas. To overcome delamination problems without resorting to helium, substrate surfaces are treated prior to deposition using a forced-pulse waterjet. Samples with different levels of roughness were prepared using both conventional and waterjet surface treatments. The samples were then coated with thick Cu using only N 2 and adhesion tests were performed. Test results show good coating adhesion on all waterjet treated substrates with bond strengths ranging from approximately 25 MPa to 58 MPa, depending on surface roughness. Consistent with previous studies, cold spray Cu did not adhere to any substrates that had been polished or grit blasted. It is shown that the pulsed waterjet creates a surface with anchoring features that interlock with incoming particles to form a strong mechanical bond.