Surface effects of alumina ceramics machined with femtosecond lasers

Laser machining is now an accepted method for shaping and modifying ceramics and is rapidly replacing other methods such as grinding and etching. In fact, new innovations such as short pulsed or femtosecond lasers have drastically decreased the amount of unwanted damage associated with laser machining. However, laser machining does still alter the surface and can change the flaw populations and the strength. In order to investigate this effect, the flaw populations and strengths of both unaltered and femtosecond laser machined surfaces were compared. Four point bend tests and a Weibull analysis were used to determine the strength and variability of each sample. From the Weibull analysis, a negligible increase in the characteristic strength was observed. However, the Weibull modulus consistently increased, thus indicating less varied values of strength for the surface treated samples relative to the unmachined samples. Fractography confirmed these findings by indicating more consistent flaw shapes on the machined surface of the specimen.