Friction and Tribo-Chemical Behavior of SPD-Processed CNT-Reinforced Composites

Abstract

Nickel (Ni) and carbon nanotube (CNT)-reinforced Ni-matrix composites were manufactured by solid state processing and severely deformed by high-pressure torsion (HPT). Micro-tribological testing was performed by reciprocating sliding and the frictional behavior was investigated. Tribo-chemical and microstructural changes were investigated using energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM) and focused ion beam (FIB). The CNT lubricity was hindered due to the continuous formation of a stable oxide layer promoted by a large grain boundary area and by irreversible damage introduced to the reinforcement during HPT, which controlled the frictional behavior of the studied samples. The presence of CNT reduced, to some extent, the tribo-oxidation activity on the contact zone and reduced the wear by significant hardening and stabilization of the microstructure.