Evaluation of Wear Properties of Ti/SiC Nano-composite Surface Layer Fabricated Using Friction Stir Processing

摘要

Friction stir processing (FSP) was employed for the fabrication of surface nano-composite layer with enhanced hardness and wear properties compared to those of the underlying commercially pure titanium (CP-Ti) substrate. Composite layers were produced by introducing nano-sized SiC powder into the stir zone. However,SiC clusters were found in the fabricated surface layers. Increasing the number of FSP passes was resulted in the formation of Ti/SiC nanocomposite surface layer with nano-sized dispersion of SiC reinforcements; this was detected using scanning and transmission electron microscopy. The fabricated nano-composite surface layer exhibited a micro hardness value of ~550HV which is about three times greater than that of the underlying CP-Ti substrate. In addition, the nano-composite surface layer exhibited superior wear resistance than the CP-Ti substrate using pin-on-disc test against the hardened AISI 52100 steel. This was associated with relatively lower friction coefficient and weight loss. The nanocomposite surface layer was found to be adherent to the underlying substrate during the pin-on-disc test. The superior wear behavior of the nano-composite surface layer is attributed to its improved micro hardness value due to the presence of hard nano-size SiC particles in a refined titanium matrix.