Wear and degradation of Co, Fe and Ni-based cemented carbides against sandstone and granite

Abstract: This diploma work is performed at Sandvik Mining and Rock Technology, Rock Tools division, a world-leading mining equipment manufacturer. The aim is to study the wear of cemented carbide rock drill inserts worn against granite and sandstone countersurfaces, with focus on the impact of binder phase composition and flushing agent chemistry. A brief introduction to rock drilling, cemented carbides and the wear and degradation mechanisms of cemented carbides in rock drilling is given. Wear is induced in a lab test by sliding cemented carbide inserts against granite and sandstone countersurfaces while flushing with deionized water or synthetic mine water. The wear is quantified by measuring material weight loss, and worn inserts are studied by SEM. All wear marks feature crushed, fragmented and heavily deformed WC grains and cavities left after individually removed WC grains. Rock adhere strongly on inserts worn against both granite and sandstone, and adhered material from both rock types sometimes endure the mechanical contact between insert and rock without significant spalling. Inserts tested with deionized water against sandstone wear 2.2 - 5.1 times more relative to against granite, and the only distinct difference observed is the distribution of adhered rock. The use of synthetic mine water relative to deionized water impacts the wear of all inserts, though corrosion products are only found on some of them. Further, the tribological contact greatly impacts the corrosive attack. The relative wear difference using different water chemistries is larger for inserts with a smaller relative amount of binder. In most cases, increased wear is measured for inserts tested with synthetic mine water. For reasons yet unknown, this trend is reversed for inserts with a high relative amount of binder tested against sandstone, where a decrease in wear is measured instead.