Femtosecond laser machining of single-crystal superalloys through thermal barrier coatings

Femtosecond laser machining of single-crystal superalloys coated with thermal barrier coatings (TBCs) has been investigated. The investigations were carried out in air using a titanium:sapphire laser system (λ = 780 nm) operating at a repetition rate of 1 kHz and delivering individual pulses of 150 fs in duration. The ablation threshold of 7 wt.% yttria stabilized zirconia (7YSZ) has been measured to be 1.52 ± 0.21 J/cm2. Microstructural investigations indicated a complete absence of conventional processing defects such as recast layers and microcracking in the vicinity of the machining area. The absence of machining-induced melting or delamination along interfaces of the TBC system demonstrates a significant advantage in comparison with conventional laser machining.