Filling the Pores of Plasma Electrolytic Oxidation Coatings on Titanium with Hydrothermal Synthesized MoS₂: Coating Structure and Tribological Performance

抄録

Although plasma electrolytic oxidation (PEO) coatings possess high hardness and good adhesion, they usually contain lots of pores and exhibit high friction coefficient. In this work, MoS₂ was synthesized via hydrothermal reaction to fill the pores of PEO coatings and improve their tribological performance. Microstructure observation of coatings shows that the porous PEO coating formed on the titanium was basically composed of Al₂TiO₅, and MoS₂ in-situ nucleated and grew on the PEO surface and in the PEO pores. The fabricated PEO/MoS₂ composite coating had a dense surface and consisted of two layers: the upper MoS₂ surface layer and the under PEO-MoS₂ interlocking layer. The tribological tests of coatings revealed that the friction coefficient of the PEO/MoS₂ composite coating (below 0.2) was much lower than that of the PEO coating (up to 0.6). The PEO coating failed after a short sliding distance of about 56 m under the normal load of 10 N. In contrast, the PEO/MoS₂ composite coating reached a much longer sliding distance up to 1000 m without failure. The excellent tribological performance of the PEO/MoS₂ composite coating was attributed to the synergistic action of PEO and MoS₂ components.

Fig. 8 Schematic diagrams of the friction and wear behavior of the PEO/MoS₂ composite coating.