Wear resistant solid lubricating coatings via compression molding and thermal spraying technologies.

This work combines two industrially friendly processing methods in order to create wear resistant and solid-lubricating composite coatings potentially suitable for high load applications. Layered composite coatings were fabricated over wrought stainless steel 444 (SS444) by compression molding a mixture of solid lubricant polymer, polytetrafluoroethylene (PTFE, 80 wt%), and wear resistant polymer, polyimide (PI, 20 wt%), onto iron aluminide (Fe 3 Al) thermal spray coatings without the need of either primers or adhesives. The fabrication process consisted of three main steps: deposition of the Fe 3 Al thermal spray coating onto a SS444 substrate and transfer into a metal mold; transfer, compress, and sinter mixed polymeric powder onto the thermal spray coating; and finally, sample cooling to room temperature. This method takes advantage of the high surface roughness of thermal spray coatings, which increases mechanical adhesion of slippery PTFE to the underlying metallic material. Coatings were produced with and without a small amount of graphite (5 wt%) to analyze its impact on sliding and wear properties. Unlike current coating technologies, the thickness of the coatings presented herein can be easily and quickly tailored by varying the amount of polymer powder added to the mold prior to compression or by grinding after fabrication. We produced and analyzed coatings ~1.3 mm in total thickness that portray coefficient of frictions ~0.1, similar to pure PTFE. The calculated wear rates for both coatings with and without graphite are an order of magnitude lower than what has been previously reported for coatings of similar composition. The influence of graphite on wear properties was found to be minimal due to the high content of self-lubricating PTFE yet can act as a way to lower material costs and increase the coatings load capacity. [Display omitted] • PTFE/PI films were deposited on Fe3Al thermal spray coatings using compression molding to produce composite coatings. • The coating method is simple and enables scalable production of polymer coatings with tailorable thicknesses. • No primer or adhesive layer was needed due to the roughness of thermal spray coatings and the addition of PI. • The well-adhered coatings were self-lubricating and portrayed wear rates two orders of magnitude lower than pure PTFE. • The addition of graphite in the polymer layer did not change tribological performance and could lower material costs. [ABSTRACT FROM AUTHOR]