In the field of dry lubricants, molybdenum disulfide is currently a popular choice, especially in aerospace applications. In contrast to other lubricants, MoS2 can withstand high loads for an extended period of time. However, the lifetime of a mos2 coating is limited by its adhesion properties with the base material.

A key aspect of adhesion between MoS2 and a substrate is the occurrence of possible chemical reactions. It is therefore crucial to ensure that the base material provides a strong binding with the molybdenum disulfide layer in order to avoid a premature coating failure.

In this study, two magnetron sputter-deposited mos2 coatings (a nanocrystalline one and a porous one) were compared to a CVD grown 2H-MoS2 single crystal using high-resolution transmission electron microscopy in selected area electron diffraction mode. The atomic structure of the MoS2 lamellae in both the as-deposited and worn coatings was investigated with a double aberration corrected Titan Themis 300 transmission electron microscope and high-angle annular dark-field scanning TEM techniques.

The morphology of the sputter-deposited MoS2 porous coating was characterised by its open porosity, which consists of a hierarchical, dendritic surface structure with interdendritic voids. In comparison, the morphology of the nanocrystalline coating is characterised by a more compact basal texture.

The tribological behaviour of the porous and polycrystalline coatings was analyzed in ball-on-disk test experiments at a load of 1.17 GPa. Both the coatings exhibited very low friction values in vacuum and ambient air. However, the sputter-deposited porous coating showed significantly higher wear rates than the polycrystalline coating. The wear behaviour of the sputter-deposited porous MoS2 was attributed to the occurrence of a non-crystalline, oxidized layer that inhibited the formation of a continuous tribo-film.