Investigation on tribological performance of LIPSS-structured nano-crystalline diamond films

Abstract

The aim of present work was to investigate the tribological behavior of CVD nano-crystalline diamond (NCD) films with laser-induced periodic surface structures (LIPSS). The LIPSS textures were fabricated in ambient air using a Yb-doped photonic crystal fiber amplifier femtosecond (fs) laser with pulse duration of 200 fs and central wavelength of 1040 nm. Two types of LIPSS texture, namely continuously distributed LIPSS (CDL) texture and a complex texture formed of evenly spaced LIPSS stripes (ESLS), were obtained with the above processing conditions. The tribological behavior of as-fabricated LIPSS textures was evaluated via ball-on-disc tests in dry reciprocating sliding motion, and ZrO2 ceramic balls were used as counterparts. In addition, there were two types of reciprocating direction involved in the frictional tests, namely the direction parallel/vertical to the orientation of LIPSS ripples. The results indicate that as the LIPSS can work as reservoir for wear debris and reduce the contact area during the friction process, the LIPSS textured NCD surface showed obviously reduced friction coefficient in comparison with the conventional NCD surface, which was reduced from 0.42 to 0.09. Besides, for the CDL surface, the friction coefficient as the LIPSS ripples vertical to the reciprocating direction was higher than that as the LIPSS ripples parallel to the reciprocating direction. In the case of ESLS surface, however, the direction of the LIPSS ripples had little influence on the friction coefficient.

Keywords

• nano-crystalline diamond films
• femtosecond laser irradiation
• lipss
• tribological performance