Depositing Metallic Coatings on Polymer Substrates by Cold Spray Process

Abstract

Abstract In this study, high pressure cold spray (HPCS) process was used to metallize the surface of polymeric substrates to improve their mechanical performance, such as erosion, wear, and strength. Thermoplastic polymer materials (PEEK, PEI, and ABS) were used as substrate. Commercially pure (CP) Al and 7075 Al were cold sprayed onto the polymeric substrates. Good quality defect-free coatings were achieved in all combinations except with ABS substrates, which suffered from distortion during CS process due to stored thermal energy. 7075Al coatings showed high adhesion strength but low thickness (low deposition efficiency (DE)), whereas CP Al coatings revealed high thickness (high DE) but poor adhesion strength. Based on the obtained results, the DE and bonding strength are not only highly sensitive to properties of the substrate, but also to the applied process parameters as well as powder morphology. It is concluded that two separate sets of spray parameters should be applied for 7075 Al and CP Al deposition otherwise, either more damage or less bonding is achieved to the substrate. Also, for each one of these powders, the first layer of metal/polymer should be deposited with a separate recipe than the subsequent metal/metal layers. Coefficient of thermal expansion and hardness difference between the coating material and the substrate were also found to be key factors to developing continuous coatings on the polymeric substrates with the HPCS process.