Preparation and tribological properties of filler-reinforced PTFE/PPS coatings deposited on textured surfaces

Abstract Graphite/SrSO 4 -filled PTFE/PPS composite coatings for sliding guideways were prepared by electrohydrodynamic atomization and deposited on polished or tree-frog-inspired textured 45 steel substrates to improve coating material retention and transfer film formation under long-term dry reciprocating sliding conditions. In the 1 h screening tests, coatings containing 0.4 g mixed fillers with different graphite/SrSO 4 mass ratios were deposited on polished substrates. Among these coatings, C2S3, with a graphite/SrSO 4 mass ratio of 2:3, showed a lower friction coefficient, better coating material retention on the worn surface and a more continuous transfer film on the counterpart surface. In the 8 h tests, three representative coatings were compared: C0S0, the unfilled coating on a polished substrate; C2S3, the selected filled coating on a polished substrate; and C2S3t, the same C2S3 coating on a textured substrate. C2S3t reduced the average friction coefficient by 47.5% compared with C0S0 and by 30.4% compared with C2S3. It also showed the lowest calculated specific wear rate among the three representative coatings. Surface profile measurements, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and Raman analyses showed that C2S3t retained more coating material on the worn surface, exhibited more continuous F and Sr distributions with a weaker Fe signal, and formed a more continuous transfer film on the counterpart surface. Durability tests further showed higher transfer film retention for C2S3t after tape-peeling, sandpaper-abrasion and high-temperature ultrasonic-cleaning tests. These results indicate that the filled coating contributes to material transfer, while the textured substrate promotes coating material retention and transfer film continuity. This study provides a decoupled design strategy for combining graphite/SrSO 4 filler-ratio selection with tree-frog-inspired substrate texturing in PTFE/PPS self-lubricating coatings for sliding guideways.