Friction and wear performance evaluation of carbon fibre reinforced PTFE composite

Recently commercialised polytetraflurotehylene (PTFE) composite reinforced with 25% chopped carbon fibres was selected for this study since details of the tribological behaviour were not available. The composite was evaluated for friction and wear performance in stringent operating conditions in adhesive as well as abrasive wear modes. The coefficient of friction (mu) and specific wear rate (K-0) of the composite in the adhesive wear mode were measured under high speeds, loads, extended sliding duration, and elevated temperatures and are reported in this paper. At moderate loads, it was observed that though it exhibited a high mu (congruent to 0.4) and low K-0 (congruent to 10(-15) m(3)N(-1)m(-1)), it showed lower mu (congruent to 0.15) and appreciably good wear performance at higher loads and moderate speeds. At higher speeds (more than 4 m/s) its performance, however, deteriorated. It was also revealed that the composite showed poor performance when tested at elevated temperatures beyond 150degreesC. A comparison with tribo-performance of neat PTFE indicated that CF reinforcement resulted in enhancement in wear behaviour very significantly. The friction coefficient, however, increased substantially. Moreover, abrasive wear performance also showed little deterioration due to carbon fibre reinforcement. Worn surface analysis by scanning electron microscope (SEM) was done to study wear mechanisms.