| Abstract: |
Metals were deposited on components made by 3-D printing with polyvinyl alcohol (PVA), a water-soluble polymer. The polymer was then dissolved, leaving a metal layer whose surface topography was the negative of that of the polymer. This is a rapid and low-cost alternative to 3D printing directly using metal, but to succeed it is essential for the sprayed metal to adhere to the polymer substrate. Tests were done in which aluminum and copper were sprayed using a twin-wire arc spray system onto on 3D printed coupons, 50 mm x 50 mm in size, made from polylactic acid (PLA), PLA mixed with metal (aluminum, copper) or carbon fiber, and PVA. Adhesion depended on substrate roughness (minimum 1-2 µm), substrate temperature (above the glass transition temperature but below the melting temperature of the polymer and the thermal expansion coefficients of the metal and polymer (thermal stresses in the coating induced during cooling should remain below its adhesion strength). It was shown that surface features could be made with high resolution on metal components using this technique.
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