Ultrashort pulsed laser ablation of zirconia-alumina composites for implant applications

Abstract

• Influence of alumina content on fs-laser machining of zirconia-alumina composites was studied. • Significant influence of material composition on material removal behavior was demonstrated. • Single phase materials have larger laser ablation thresholds and smaller material removal rate than their composites. • A lower scan speed is preferred for single phase materials while a higher scan speed is beneficial for the composites. Laser texturing of zirconia-alumina ceramics is a promising surface modification method for many applications, such as enhancing osseointegration of alumina toughened zirconia (ATZ) dental implants or improving friction behavior of zirconia toughened alumina (ZTA) hip replacement bearing components. The common problems in laser texturing of ATZ/ZTA ceramics are thermal cracking, low material removal rate (MRR), and laser-induced phase transformation (LIPT). Furthermore, the compositional variation of those ceramics will complicate these problems. In order to improve the manufacturing processability, ultrashort pulsed laser ablation behavior of ATZ/ZTA composites was investigated in this research. Single phase zirconia and alumina were found to have smaller MRRs than their composites, and this behavior was negatively correlated to the materials single-pulse laser ablation threshold. However, under multi-pulse laser irradiation, the ablation thresholds of all materials saturated to the same level, indicating that single phase materials were more sensitive to the incubation effect than their composites. This led to the MRRs of the single phase materials being reduced at larger scan speeds, while the MRRs of their composites remained independent of scan speed. It was also shown that single phase materials were less susceptible to thermal cracking than their composites under excessive heat accumulation. These results suggest that a lower scan speed is preferred for single phase materials in order to achieve a larger MRR, while a higher scan speed is beneficial for the composites for suppressing thermal cracking without compromising ablation efficiency. In addition, no LIPT was detected for zirconia dominated materials after laser ablation.