FAILURE ANALYSIS OF CARBIDE TWIST-DRILL BIT FOR SMALL-SCALE GRANITE DRILLING

This paper deals with a failure analysis of WC-Co carbide-based twist drills used for small-scale granite drilling. A bench-top drill was used for this study. The aim of the study was to analyse a simulated in-situ rock-drilling operation normally carried out in mines. After a drilling time of 15 minutes, the drills were examined using scanning electron microscopy. On macroscopic observation, both cutting edges of the drills showed slight signs of abrasion, but these were not significant. The chisel edge was also abraded and showed some macroscopic abrasion marks. The electron micrographs showed various signs of decomposition at the micro and nano levels, including cracks in the WC grains, cavities in the grains, Co-binder erosion and some heavy abrasion marks. In addition, some parts of the carbide grains were covered with a thin layer of rock. The wear analysis is an important approach to understanding exactly the damage behaviour of the tool so that the material composition can be changed to avoid premature tool failure.