Tribological Characterization of Micron-/Nano-Sized WC-9%Co Cemented Carbides Prepared by Spark Plasma Sintering at Elevated Temperatures

Abstract

The present study investigates the high temperature tribological performance of spark plasma sintered, nano- and micron-sized tungsten carbide (WC) bonded by 9 wt.% cobalt (Co). The composites were fabricated using a two-step procedure of mixing followed by spark plasma sintering (SPS). Ball-on-disc wear tests were conducted at a normal load of 30 N, linear speed of 0.1 m/s under dry conditions and at three different temperatures (room temperature, 300 °C and 600 °C). Field emission scanning electron microscopy (FESEM), optical profilometry and energy dispersive X-ray (EDS) spectroscopy were used to analyze the surface morphology and the wear track area. At room temperature, it was observed that the nano-sized WC composites exhibited better wear resistance than the micron-sized WC composites. The wear resistance of the nano-sized samples declined significantly relative to that of the micron-sized samples with an increase in temperature. This decline in performance was attributed to the higher surface area of nano-sized WC particles, which underwent rapid oxidation at elevated temperatures, resulting in poor wear resistance. The wear rate observed at 600 °C for the micron-sized WC composites was 75% lower than that of the nano-sized cemented carbide. Oxidative wear was observed to be the predominant wear mechanism for both cemented carbide samples at elevated temperatures.