Polymer metallization via cold spray: an investigation into the effects of particle hardness and morphology

Metallization on polymers has captured remarkable attention across both industry and academia, facilitating the integration of unique features of polymer and metals. Particularly, direct metallization on polymers is critically important as it eliminates the need for surface activation, substrate heating, and post-processing. In this study, cold spray (CS) particle deposition was employed for direct metallization of a polymer substrate − Acrylonitrile Butadiene Styrene (ABS) − with a focus on characterizing the influence of particle (powder) hardness and their morphologies on resulting deposition. In this regard, both spherical (sp) and irregular (ir)-shaped, copper (Cu) and aluminum (Al) feedstock powders were utilized, acknowledging that Cu is intrinsically harder than Al. The metallization process on the substrate was studied in terms of microstructure, deposition efficiency, film thickness, and adhesion strength. The experimental results showed that the Cu powders achieved higher deposition efficiency (≈2.2-fold for ir-shaped, ≈2.1-fold for sp-shaped), film thickness (≈4.4-fold for ir-shaped, ≈6.4-fold for sp-shaped), and adhesion strength (≈1.9-fold for both ir- and sp-shaped) compared to the corresponding Al powders. Additionally, Cu powders exhibited lower surface porosity (24 % for ir-shaped, 20 % for sp-shaped), in contrast to the Al powders (51 % for ir-shaped, 31 % for sp-shaped). On the other hand, for both types of powders, the ir-shaped powders exhibited higher deposition efficiency (≈1.6-fold for Al and ≈1.7-fold for Cu) than the sp-shaped powders. However, irregular-shaped powders resulted in higher surface porosity (≈51 % for Al-ir, ≈31 % for Al-sp, ≈24 % for Cu-ir, ≈20 % for Cu-sp). Notably, no significant difference in adhesion strength was observed between the spherical and irregular-shaped powders. The findings elucidate the intricacies of the CS technique, contributing to functional metallization on polymeric substrates.