Development of Thermal Spray Processes for Depositing Coatings on Thermoplastics

Abstract

Thermoplastics combine high freedom of design with economical mass production. Metallic coatings on thermoplastics enable power and signal transmission, shield sensitive parts inside of housings and can reduce the temperature in critical areas by functioning as a heat sink. The most used technical thermoplastics are polyamides (PA), while the described use cases are often realized using Cu. Consequently, several studies tried to apply copper coatings on PA substrates via thermal spraying; so far, this combination is only feasible using an interlayer. In this study, a new approach to metallize thermoplastics via thermal spraying based on validated state-of-the-art predictions of the thermoplastics’ material response at relevant temperatures and strain rates is presented. Using these predictions, high velocity wire-arc spraying was selected as coating process. Furthermore, the process parameters were adapted to realize a continuous coating while also roughening the substrate during coating deposition. The resulting Cu coating on PA6 had a sufficiently high coating adhesion for post-treatment by grinding. The adhesion is achieved by in situ roughening during the coating application. The results indicate that different process parameters for initial layer deposition and further coating buildup are required due to the low thermal stability of PA6.

Thermal Spray Coatings for Electromagnetic Wave Absorption and Interference Shielding: A Review and Future Challenges

“…[166] While there are numerous examples where material has been doped with REEs using techniques other than thermal spray to improve EM wave propagation characteristics, such as chemical coprecipitation [167] or hydrothermal synthesis, [156] it is also possible that doping certain REEs during thermally sprayed coatings could also help improve the EM propagation wave characteristics of materials. In an example, Bartuli, Cipri and Valente (2008) [70] used a range of complex ceramic-based composite coatings, which included lanthanum/La REE (e.g., Cr 2 O 3 þ La 0.5 Sr 0.5 MnO 3 40wt%, Cr 2 O 3 þ Al 20 wt% þ La 0.5 Sr 0.5 MnO 3 20wt%) fabricated by air plasma spraying to evaluate their tailored EM properties (essentially as absorbers in the microwave range (8)(9)(10)(11)(12)). However, thermal spraying can make REEs prone to oxidation during processing and operation, and oxidation can lead to brittle coatings and deterioration of magnetic properties.…”

“…[ 9 ] As will be seen later, the substrates in such thermally sprayed coatings varied from metals, alloys, glass, and ceramics to graphite; however, there is little or no evidence where lightweight polymeric substrates were considered for EM wave propagation applications. Though not a focus of current review, application of polymeric substrates (e.g., thermoplastics, which are excellent electrical and thermal insulators) is quite possible with some degree of limitations, as demonstrated by Bobzin, Wietheger, and Knoch (2021), [ 10 ] as such materials can well be combined with a high degree of design flexibility and economical mass production.…”

On the Importance of Secondary Component Properties for Cold Spray Metallization of Carbon Fiber Reinforced Polymers

“…Vacuum deposition techniques, such as physical vapor deposition (PVD) (Ref 5 ) or chemical vapor deposition (CVD) (Ref 6 ) have provided potential pathways to metallization of polymers but they are not suitable to fabricate thick metal coatings (over 100 µm) (Ref 7 ). Other techniques have been considered such as layup molding (Ref 8 ), wire-arc spray (Ref 9 - 12 ), flame spray (Ref 13 ), plasma spray (Ref 14 ) or air plasma spray (Ref 15 , 16 ), but cold spray has appeared as one of the most viable approaches as it uses relatively low temperatures (several hundred degrees versus several thousand degrees for other thermal spray techniques), thus limiting the risk of oxidation of the metallic powder and heat damage to the substrate (Ref 17 ).…”

Simulation Analysis on the Jet Flow Field of a Single Nozzle Spraying for a Large Ship Outer Panel Coating Robot

“…Based on these predictions, highspeed arc spraying was chosen as the coating process. In addition, the process parameters were adjusted to achieve continuous coating [12].…”