Crystallization kinetics of machinable glass ceramics produced from volcanic basalt rock

This study investigates the utilization of basalt in manufacturing machinable glass ceramics. As the fluorine and potassium phases, MgF2 and K2O added into basalt are responsible for the machinability of glass ceramics. Three different compositions containing 80%, 85%, and 90% basalt, with K2O and MgF2 as the remainder, were mixed and melted in an alumina crucible at 1500 °C. Glass samples were obtained by casting the melt into a graphite mould. Glass ceramics were prepared through subsequent crystallization heat treatment of the obtained glass. Compositional and mechanical characterizations were carried out via XRD-SEM and hardness/fracture toughness and machinability tests respectively. The effect of change in the obtained phases with basalt composition on the machinability of glass ceramics was investigated. Furthermore, crystallization kinetics of the glasses were investigated by differential thermal analysis (DTA) using the Kissinger kinetic model with several different heating rates. This study reports that basalt can be utilized in the production of machinable glass ceramics only if the basalt ratio is justified. The results showed that good machining performance was observed in low-basalt content conditions (B80), When the basalt content increased (B85 and B90), the machining capability decreased markedly. Furthermore, the crystallization activation energies decreased with increase in basalt content.