Laser-based process for polymeric tribological coatings on lightweight components

Due to excellent material properties, coatings based on high-temperature resisting thermoplastic polymers like PEEK (polyether ether ketone) represent a promising alternative to conventional tribological coatings based on sliding lacquer. Since the conventional, oven-based coating process requires heating the entire component above the melting temperature of PEEK (approx. 340 °C), it is not suitable for temperature-sensitive base materials (e.g. aluminum alloy AlMgSi1). Hence, with the objective of significantly reducing the thermal load of the workpiece and enhancing the process energy efficiency, a laser-based coating process is investigated by the authors. The current research is primarily focused on the process development for the two laser-based process steps. Firstly, the influence of a laser pre-treatment on the surface topography and the adhesion of the PEEK coating is investigated. Secondly, the laser-based coating process is evaluated with regard to the relative density of the coating. As a result, dense and adherent tribological coatings can be applied on aluminum substrates. The adherence is significantly increased by a laser-based pre-treatment of the substrates. The minimal interaction time for generating dense coatings is approximately 7 s which represents a decrease by a factor of > 100 in comparison to oven processing.