Electroless Plating of Ni-P and Ni-P-PTFE on Micro-Arc Oxidation Coatings for Improved Tribological Performance

Although micro-arc oxidation (MAO) coatings are widely used for anti-wear protection of metals, they usually contain lots of pores and exhibit high coefficient of friction. In this work, porous MAO coatings consisting of Al2TiO5 were fabricated on the titanium substrate, and then Ni-P and Ni-P-polytetrafluoroethylene (PTFE) were deposited via electroless plating to fill MAO pores and improve the tribological performance. Electroless deposited Ni-P has high wear resistance and the incorporated PTFE particles have self-lubricating property. Results show that the micro-pores of the MAO coating were completely filled by deposited Ni-P and Ni-P-PTFE, and the self-lubricating PTFE particles distributed uniformly in the coating. For the MAO-Ni-P-PTFE coating, the MAO and Ni-P components mechanically interlocked and played a load-carrying role during the tribological test, and the dispersed PTFE particles produced low friction. Compared with the MAO and MAO-Ni-P coatings, the MAO-Ni-P-PTFE coating exhibited much lower coefficient of friction and wear rate.