Fiber laser processing of thick Yttria stabilized Zirconia

A novel laser processing technique is demonstrated for cutting up to 13mm thick sections of Yttria-stabilized Tetragonal Zirconia Polycrystal (Y-TZP) ceramic. Y-TZP is a high toughness engineering ceramic which is extremely difficult to machine in its final state. However for some applications this is nevertheless desirable. As an example Y-TZP based dentures represent an example of mass-customization in which it is essential to machine the required shape from solid billets rather than to produce customized moulds. Currently this is done mechanically and necessitates the use of diamond tipped grinding and drilling tools, however this process is a very slow and suffers from problems of high tool wear. In this work a Ytterbium fiber laser system has been used to achieve full thickness cuts via a novel controlled crack propagation technique. This results in a limited surface heat affected zone and no cracking is observed to propagate into the bulk material. Processing rates are substantially faster than alternative cutting techniques available for this material with feed rates of up to 1.8 mm/s demonstrated. A finite element model is used to achieve a better understanding of the cutting mechanism.