EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

In general, uncoated polyamide tends to have a relatively high wear rate if polyamide is integrated in sliding systems (e.g. hinges, bearings, rack rails). As a consequence of that any kind of material failures will occur much faster than with a low friction coating.
Deposition strategies to obtain low friction and wear resistant coatings on 3D-printed, rough polyamide 12 (PA) surfaces were developed by atmospheric pressure plasma deposition. Dry lubricants such as MoS2 and graphite were fed as powder material to the plasma jet (Inocon Technologie Ges.m.b.H.), applying parameter sets without thermal damage of the heat sensitive PA. In general, microtribological characterization indicates that especially the chemical coating composition and thickness has high influence on the coating performance. Pure MoS2 coatings are quickly worn, especially on roughness tips of the quite rough coatings (roughness Ra up to 20 µm), exposing the substrate locally and leading to friction coefficients similar to PA12 and rather limited potential of wear protection. Compound coatings with graphite within a MoS2 matrix provide huge potential for wear protection (>20 times less penetration depth) even in the case of exposing PA12 to roughness tips, due to the transfer of lubricating carbon into these exposed areas. If the thickness is sufficiently high, missing wear of tips results in low-friction behavior with friction coefficients <0.1 (thus, 4 times lower than for uncoated PA12).