Friction and wear durability study of epoxy-based polymer (SU-8) composite coatings with talc and graphite as fillers

SU-8, an epoxy-based polymer, is industrially very useful material for fabricating microsystems such as micro-electro-mechanical systems. However, for optimal performance, it is necessary to further improve the mechanical and tribological properties of SU-8. Different weight percentages (wt%) of graphite and talc particles are added to SU-8 for the enhancement of mechanical as well as tribological properties. The composite with the optimized composition of SU-8+15 wt% graphite+15 wt% talc has shown superior properties compared with pure SU-8 and other composites tested. This composite shows ~4 times lesser steady-state coefficient of friction (~ 0.2), ~3 times higher elastic modulus (~7.97 GPa) and ~2 times greater hardness (~0.52 GPa) over those of pure SU-8. Also, there is a decrease in the wear rate by ~103 times. This optimized composite, which showed nano to micron scale texturing on the surface, has performed better in comparison with single or mixed fillers with different wt% ratios. The wear mechanism for filler content up to 10 wt% was found to be fatigue and delamination, whereas for higher filler content the abrasive wear mechanism was dominant.