Friction between a cemented carbide rock drill button and different rock types

WC/Co cemented carbide is the most common material for rock drilling due to its superior combination of toughness and hardness. To elucidate the relationship between the known wear behaviour against different rock types and the corresponding sliding friction performance, a friction test series has been performed. A cemented carbide rock drill button with 94-wt.% WC and 6-wt.% Co was sliding against polished granite, magnetite, hematite, quartzite, mica schist, leptite and sandstone in a pin-on-disc tribometer. The test was performed in 25 °C and 350 °C air and also in 25 °C water. The load was chosen to 20 N (which is considerably lower than required for crushing the rock) and the sliding velocity was 0.26 m/s. At 25 °C, the cemented carbide exhibited the highest stable dry friction against mica schist, and the lowest against leptite. At 350 °C, leptite gave the highest friction and hematite the lowest. In water, granite showed the highest friction and quartzite the lowest. A “remaining water lubricant effect” was noticed where mica schist was able to keep low, water lubricated friction value even when seemingly run dry, while leptite, sandstone and hematite were not.