Femtosecond laser modification of multilayered TiAlN/TiN coating

A target of multilayered TiAlN/TiN coating deposited on steel was irradiated by 200 fs pulses of a Ti:Sapphire laser, operating at 775 nm. Laser fluences of 1.16 J cm− 2 to 116 J cm− 2 produced a range of modifications, from well defined parallel surface structures on the coating, to deep craters in the substrate. Parameters for coating ablation were determined in terms of laser fluence and pulse count. A single-pulse damage threshold was found to be 0.66 J cm− 2 and the damage incubation factor 0.642. At lower laser fluences formation of laser induced parallel surface structures was evident, beginning from the first pulse, with a periodicity of about 580 nm. These structures remained and were pronounced at the rim of the damage spot even when the coating was completely ablated in the centre.