An investigation into the surface, friction and wear properties of laser sintered polyamide-12 components

Polymer Laser Sintering (LS) is an Additive Manufacturing process that is well-established due to its ability to produce functional components with highly complex geometries. However, the adoption of these components for end-use applications remains hindered due concerns regarding their in-service behaviours, particularly when subject to dynamic contact. Therefore, the scope of this investigation was to characterise the surface, friction and wear properties of polymer laser sintered components to help address these issues. More specifically, Polyamide-12 was selected to be the principal polymer of interest for this investigation as it currently dominates the LS materials market.

Laser sintered Polyamide-12 surfaces were first studied in detail. Results showed that their topographies were dependent on their build orientation, particularly top surfaces, which were found to be asperity peak dominated due to the mechanism of finish layer powder particle adhesion. Moreover, it was demonstrated that it was possible to reduce the top surface heights of laser sintered Polyamide-12 components by as much as 68% when alternative build actions were employed.

Dry sliding tests were then performed to ascertain insight into the friction and wear properties of laser sintered Polyamide-12 components. This included investigating how varying operating conditions, specifically normal load, sliding speed and contact configuration, influenced both their transient and steady-state sliding behaviours. Additionally, incorporating solid lubricants within Polyamide-12 matrices was explored as a potential means of modifying the tribological properties of components manufactured by LS. Ultimately, it was demonstrated that the individual additions of Polytetrafluoroethylene and Molybdenum disulphide reduced the magnitudes of friction and wear incurred during testing by as much as 50% and 78%, respectively.

This was the first time knowledge between tribology and polymer Laser Sintering was comprehensively consolidated. Consequently, new correlations between material, process and resultant surface and sliding phenomena were established.