Experimental investigations into surface crack density and micro hole dimensions during ultrashort pulse laser ablation

In this work, an attempt has been made to understand the nested concentric and Z-path laser scanning paths interaction with thermal barrier coating (TBC) titanium alloy using ultrashort pulse laser.Ablation threshold is evaluated at various repetition rates (RR) and laser fluence for nested concentric and Z-path movement.Detailed investigations have been conducted to study the influence of RR, pulse overlap (PO), laser fluence, and the number of laser scans on surface crack density (SCD), hole diameter and depth.It is inferred that ablation threshold saturation is obtained after a critical RR of 20 kHz and 10 kHz for nested concentric and Z-path, respectively.Micro hole diameter and depth are highest at critical RR.Nested concentric scanning path movement provides better hole morphology than Z-path movement at 2.29 J/cm 2 , however, the Z-path increased the hole depth by 25 m at 1.78 J/cm 2 .