Growth and characterization of integrated nano- and microcrystalline dual layer composite diamond coatings on WC-Co substrates

► Nano-microcrystalline diamond layers were integrated with transition layer (~ 1 μm). ► Stable friction coefficient ~ 0.06 and nanohardness ~ 96 GPa were observed. ► Integrity of the CVD diamond coatings was uncovered by cross-sectional studies.