The effect of coating thickness on the tribological properties of polydopamine/PTFE + graphite particle coatings on 60NiTi

Polydopamine (PDA)/polytetrafluoroethylene (PTFE) + 0.25 wt% graphite particle (GrP) coatings of three different thicknesses were deposited on roughened 60NiTi substrates. Their tribological properties were evaluated by coating durability, wear progression, and scratch tests. It was found that the thicker coatings have longer wear life, but the wear life was not proportional to the coating thickness. The coating thickness affected the transfer film and contact pressure and thus the coating durability. The coating wore rapidly to the coating-substrate interface and then wore at a very low wear rate. The thicker coatings had lower critical loads at which gross coating failure occurred.