Influence of material composition on nanosecond pulsed laser micromachining of zirconia-alumina composites

Abstract

Due to their excellent mechanical properties and biocompatibility, zirconia-alumina composites are promising materials for bio-implant applications, including dental and hip-joint implants. A higher content of zirconia phase is beneficial for the fracture toughness of the composite material and therefore is more suitable for dental implant applications, while alumina is more resistant to wear than zirconia, and alumina dominated composite is therefore more often used in hip-joint implants. Studies about laser micromachining of both single phase zirconia-alumina and their composites are available in literature. However, the understanding on how the relative content of the two phases will affect the micromachining performance is lacking. In this paper, the influence of material composition on nanosecond-pulsed laser micromachining performance of zirconia-alumina composites is investigated by varying alumina content. Single pulse spot machining and groove machining experiments were performed on four graded ceramics with different alumina contents. The influence of laser parameters, including laser pulse energy, pulse width, pulse repetition rate, and scanning speed on material removal behavior and surface characteristic were investigated experimentally. It was found that materials with lower content of alumina phase were easier to be machined, which characterized by higher material removal rates, than high alumina contained materials. In addition, lower alumina content ceramics were more susceptible to thermal cracking than higher alumina content ceramics under excessive laser energy input. Besides, the inhomogeneity of the microstructure of the zirconia-alumina composites was found to have substantial influence on the morphology of the spots machined with short laser pulses. This research shows the significant influence of material composition on laser processing performance and should be helpful in selecting of optimal laser parameters for achieving desirable machining quality in laser processing of zirconia-alumina composites.