Microstructure and self-lubricating property of a novel Al2O3/La2P4O13/MoS2 composite layer in-situ prepared by micro-arc oxidation

Abstract

A novel Al₂O₃/La₂P₄O₁₃/MoS₂ composite layer was successfully in–situ prepared on 6082-T6 alloy surface utilizing micro-arc oxidation (MAO) technology by introducing Na₂MoO₄, Na₂S, and C₂H₆LaO₃ into the electrolyte. The microstructures, compositions, morphologies and tribological behavior of the composite layer are characterized by XRD, XPS, SEM, EDS, TEM and UMT. The results show that: with the increase of C₂H₆LaO₃ concentration, the surface roughness changed from 1.447 to 2.588 μm, the porosity changed from 3.79 to 2.45 % and the hardness rises from 737.66 to 1177.41–1260.44 HV₁; the self-lubricating phases La₂P₄O₁₃ and MoS₂ were dispersed between the hard phase Al₂O₃; when the concentration was 5 g/L, the average friction coefficient is reduced by 41.66 % compared with the Al₂O₃/MoS₂ composite layer at 0 g/L. There was no obvious mass or volume changes of coupled body (Si₃N₄ balls) before and after sliding wear. The in-situ formation of MoS₂ and La₂P₄O₁₃ in the MAO layer can have a coordinate effects for improving the compactness, hardness and self-lubricating behavior.