Wear properties of cemented carbides with new binder solutions for rock drilling inserts

Abstract

Cemented carbides with tungsten carbide grains as hard phase and metallic cobalt binder phase are used extensively for drill bit inserts for rock drilling. The process of rock drilling is severe with some of the wear happening through fracture in the cemented carbide. This work investigated two cemented carbides with iron rich alternative binder phases containing different amounts of FCC phase, intended to minimise the fractures through formation of a BCC phase. The samples are tested next to a reference with cobalt binder and investigations of the as-sintered samples show only very small differences in many of the relevant properties and microstructural features, including hardness, toughness, grain size distribution and binder phase volume fraction. The main difference found is in the amount of FCC in the binder phase microstructure. In a rock turning test it is found that both alternative binder drill bit inserts perform better than the reference with cobalt binder phase, studies of the wear scars show that the wear progresses though fracture of material in all samples with no discernible differences seen. There is however a correlation between volume fraction of FCC in iron-based binders and reduced wear, showing that the concept is promising for further studies.