Surface damage on cemented carbide rock-drill buttons

Wear phenomena on cemented carbide drill buttons tested in percussive drilling of Kiruna-magnetite under realistic conditions have been studied with scanning electron microscopy, light optical microscopy and energy dispersive X-ray spectroscopy. In addition, a comprehensive literature study has been performed. The aim has been to chart wear phenomena, such as crack formation, occurrence of reptile skin and various wear mechanisms. It is shown that surface cracks form shortly after drilling has started. Also the valleys and plateaus characterising the reptile skin pattern were found after only short drilling periods. It appears that the formation of the initial surface cracks and the reptile skin pattern are separate mechanisms, which presumably interact. In addition to the formation of cracks, there is also a continuous wear of the buttons. This is assumed to be caused by wear fracturing and pullout of tungsten carbide (WC) grains and wear of cobalt (Co) by abrasion, possibly assisted by corrosion. A wear mechanism table, based on a comprehensive literature review and on experience from real drilling conditions, is suggested.