Surfactant-Free Electroless Codeposition of Ni-P-MoS2/Al2O3 Composite Coatings

This paper presents the influence of an inorganic Al2O3 layer over MoS2 particles on the tribological performance of electroless Ni-P-MoS2/Al2O3 composite coatings fabricated without using surfactants. The Al2O3-coated MoS2 particles were prepared by a heterogeneous nucleation process. The dry sliding tests of the composite coatings were tested against a WC ball. SEM was used to observe the surface morphology of particles, composite coatings, and worn surfaces. The results indicate that the coverage of an Al2O3 coating on MoS2 particles significantly affects the surface morphology, frictional coefficient and wear loss of the composite coatings. The incorporation of Al2O3-coated MoS2 particles with lower coverage (up to 7% of Al2O3) could obtain compact surface structure of composite coatings, which contribute to reduced wear loss. However, higher coverage would lead to loose surface structure of the composite coatings, and thus increase their wear loss.