Fracture mechanics-based analysis for hybrid laser/waterjet (LWJ) machining of yttria-partially stabilized zirconia (Y-PSZ)

Conventional machining of yttria-partially stabilized zirconia (Y-PSZ) is difficult and time consuming due to its high strength and fracture toughness. A non-traditional hybrid laser/waterjet process that combines CO2 laser and abrasive-free waterjet (LWJ) was investigated for cutting of Y-PSZ substrates. The hybrid system exploits the low thermal shock resistance of Y-PSZ for controlled crack propagation along cutting path through localized heating and rapid quenching by laser and waterjet, respectively. Analytical solutions for temperature and stress fields in the workpiece during laser heating and waterjet quenching were developed and were used to identify the processing parameters required for controlled separation of Y-PSZ substrates. Cutting experiments were performed for a number of different processing parameters and cut surfaces were analyzed to identify the mechanisms responsible for observed fracture. Experimental results were compared with theoretical predictions to validate the modeling assumptions underlying analytical models of the hybrid cutting process. The experimentally validated model of the cutting process relates processing parameters to the different modes of machining of the workpiece and can be effectively used for hybrid cutting of Y-PSZ substrates.