FRACTURE ANALYSIS OF CEMENTED-CARBIDE INSERTS FOR THE DRY CUTTING OF REPEN LIMESTONE

This paper presents the results of an investigation into optimising dimension stone Repen extraction from Debela Griža quarry. Firstly, this was done by optimising parameters of Fantini GU.70-R/XC cutting chainsaw; it was determined that relatively quick Repen cutting can be achieved using the axial force of its blade between 40 and 75 N. Secondly, a few fractured and unfractured cemented carbide (WC-Co) inserts were metallographically prepared and examined under light optical microscope and SEM with EDS. Later, the samples were also etched for the presence of η-phase and had Vickers hardness tests performed on them. Fracture surface analysis showed that the main reason for insert fracture was hitting harder intrusions in stone. Furthermore, most of the fractured inserts had carbide grains smaller than 2,5 μm, thereby having lower fracture toughness. It was also discovered that samples with higher binder content and larger carbide sizes exhibited lower Vickers hardness. One of the fractured inserts also contained η-phase, further increasing its susceptibility to fracture.