Effect of bottom micro-crystalline diamond (MCD) layer and top nano-crystalline diamond (NCD) layer onto the tribological behavior of (MCD/NCD) bilayer film

In this study, a comparative study of a series of (MCD/NCD) bilayer films with different MCD grain sizes and NCD layer thickness deposited on cemented tungsten carbide (WC-Co) flat substrates was conducted by changing the deposition time. Tribological behaviors of these diamond films were evaluated by using a reciprocal tribometer without lubrication. In friction test against Si3N4 balls, the (3hMCD/6hNCD) bilayer film showed the lowest coefficient of friction (0.059) and wear rates of counterpart balls (1.75 x 10(-6) mm(3) N-1 m(-1)) because of its lowest surface roughness and higher sp(2) content. This work provides a guide to choose suitable (MCD/NCD) bilayer basic structure in multilayer diamond film for getting a fine diamond film with low roughness and great tribological performance for different applications.