Friction coefficient and linear wear rate of polyester-carbon nanotubes composites were investigated through ball-on-flat reciprocating test, under dry sliding contact. Three types of nanoscopic fillers were used: multiwall carbon nanotubes (MWCNT), functionalized multiwall carbon nanotubes (MWCNT-COOH) and singlewall carbon nanotubes (SWCNT), with three values of weight content 0.1, 0.15 and 0.2 wt%. Comparative analysis was done for polyester and its composites tested over 14 m sliding distance, under three values of load, 30 N, 40 N and 50 N. Composites containing MWCNT underwent a decrease in friction coefficient and linear wear rate only in case of 50N loading. An improvement of wear behavior under 50N loading was obtained for the composite with 0.10 wt% functionalized carbon nanotubes. Generally, better values of wear rate at 50 N loading were recorded in case of composites with 0.15 wt% and 0.20 wt% MWCNT and SWCNT, respectively. Optical and electronic investigation of the worn surfaces revealed the occurrence of abrasive, adhesive and fatigue wear. Abrasive wear is due to the hard particles detached from the counterpart which produce scratches and furrows on sliding track. Adhesive wear results when soft particle of polymer are caught and blocked among the asperities of counterpart, and it develops over a local area, being influenced by temperature rise. Fatigue and abrasive wear are responsible for the formation of the 3rd body between contacting parts which affects the friction and wear behavior. Morphological analysis of worn surface showed the rise of transfer film that induces instability of wear parameters.
Tribo-Mechanisms of Carbon Nanotubes: Friction and Wear Behavior of CNT-Reinforced Nickel Matrix Composites and CNT-Coated Bulk Nickel
