Tribological behaviors of the diamond films sliding against the T800/X850 CFRP laminates

Abstract

The frictional resistance and hole quality when drilling CFRP laminates are associated with tribological behaviors of drill materials. In the present study, tribological tests are conducted on various diamond coated WC-Co balls sliding against T800/X850 CFRP laminates with [-45/90/45/0]s lay-up, under specific conditions similar to the drilling process. It is firstly found that the coefficient of friction (COF) varies with the sliding direction. The boron-doped micro-crystalline and nano-crystalline composite diamond (BDMC-NCCD) film synthesized by optimized growth durations (9 h for BDMCD and 2.5 h for NCD) presents relatively low COF and wear rate (0.193 and 0.97 × 10−8 mm3/N m, when the sliding velocity and normal load are respectively 1.5 m/s and 5.0 N), as well as high critical load for the film peeling (35 N), owing to the nano-sized diamond grains and low surface roughness (Ra~125.09 nm measured by the confocal microscopy) of the surface NCD layer, and high hardness and favorable adhesion of the underlying BDMCD layer. Besides, influences of the sliding velocity and normal load are clarified, indicating that the COF increases with the load, but decreases with increasing the velocity, while the wear rate increases with either the load or velocity.