Comparative study of simplex doped nc-WC/a-C and duplex doped nc-WC/a-C(Al) nanocomposite coatings

The existing challenges due to severely operating conditions of mechanical components require developing solid lubrication coatings with high hardness, good toughness as well as low friction coefficient. In this paper, the simplex W-doped nc-WC/a-C and duplex doped nc-WC/a-C(Al) nanocomposite coatings were successfully fabricated using magnetron sputtering process. The microstructure, mechanical properties and tribological behaviors of as-fabricated coatings were comparatively investigated. Results show that the WC1−X nanocrystallites were formed and uniformly dispersed in the amorphous carbon matrix, while co-doping Al in the nanocomposite coating could drastically diminish the magnitude of internal stress and improve the adhesive strength as well as maintain the moderately high hardness. The significant improvement in the tribological performances of duplex doped nc-WC/a-C(Al) coating was mainly attributed to superior mechanical properties and the formation of continuously compacted graphitized tribofilm under dry friction as well as WS2-containing tribofilm under oil lubrication. The good balance between hardness and toughness, low internal stress, superior low-friction and anti-wear properties of duplex doped nc-WC/a-C(Al) nanocomposite coating make it a good candidate as solid lubricating coating in engineering applications.