Anti-Icing Coatings Manufactured by Cold Gas Dynamic Spray and Icephobic Performance Evaluation

Abstract

Ice accumulation is a recurring issue in various industries exposed to atmospheric icing, often causing severe damage, disruptions of continuous operation and substantial efficiency losses. Current mitigation methods require complex engineering considerations and intensive energy requirements. Alternative solutions are being explored, including ice release coatings (icephobic coatings) which use their surface and chemical properties to protect a structure from ice accretion. Several materials are naturally icephobic in a bulk material state however, to be useful in real-world applications, they are required to be in coating form. Current processes used to apply these materials as coatings can deter icephobic properties if not executed properly. Cold gas dynamic spray (CS), a green additive manufacturing method, is considered as an alternative process as it does not melt its feedstock material, thus preserving initial material properties. Two icephobic materials are investigated in this work, including their CS deposition and icephobic performance. Firstly, studies focusing on the cold spray deposition of polymers remains poorly understood and inefficiently executed in the field. The use of a supersonic flow produced by commercial CS nozzles remains the standard and often include complex nozzle alterations to accommodate the polymer feedstock. As a result, this work presents a new nozzle, designed using numerical simulations, and experimental results are used to characterize its deposition behavior. The new nozzle demonstrates that CS can efficiently produce polymer coatings on metallic substrates without the use of a complex flow and using commercially available components. The icephobic performance of coatings produced with the new nozzle are then characterized using the three components that make up atmospheric icing: the ability to 1) shed water droplets through hydrophobicity, 2) delay the ice nucleation and growth process, and 3) reduce overall ice adhesion properties. The as-sprayed polymer coating demonstrated a superhydrophobic behavior at room temperature, however its beneficial complex surface hierarchy led to degrading icephobicity at low temperatures. Under various frosting conditions, the coating’s wetting state became compromised prior to solidification, which demonstrated that other studies claiming superhydrophobic surfaces can also be icephobic are in fact incomplete. Secondly, literature has shown that bulk complex metallic alloys, such as quasicrystals (QC), have unique icephobic properties, in addition to being very durable materials. However, the intrinsic brittleness and hardness of these materials render their application as a coating very challenging. The use of the CS process for this material is especially difficult as it relies heavily on plastic deformation for the bonding of particles with the substrate. This work investigates the deposition of QCs through process parameter mapping, intensive particle pre-heating to thermally soften the feedstock, and through the addition of a softer metallic phase for the creation of a ceramic-metal matrix composite (cermet) coating. The work shows that QCs require further investigation if they are to be cold sprayed without the use of feedstock pre-heating. However, when subjected to intensive pre-heating, they have shown to be a promising first step in the deposition of full QC coatings. In addition, their use as the ceramic phase in a cermet coating has shown to be a successful alternative, despite having minor retention of the QC phase in the final coating.