No abstract

No abstract

A double layer a-CN/TiAlN coating deposited on ASP30 steel substrate was irradiated by femtosecond laser and surface modification effects were observed. Moderate laser intensities used were in the range of 1014–1013 W/cm2, while the total thickness of double layer coating was 4.8 µm (a-CN = 0.6 and TiAlN = 4.2 µm). Laser-induced changes of the surface showed dependence on laser intensity and number of accumulated pulses. Irradiations at the highest intensity resulted in preservation of one or both layers up to 10 pulses, while at lower intensity (1013 W/cm2) a-CN layer is removed after several pulses and TiAlN is preserved up to 50 pulses. Evaluated damage threshold of the target was 0.49 J/cm2. Lower laser intensity irradiation produced periodic surface structures (LIPSS) over the entire irradiated spot with periodicity of ~700 nm, almost in agreement with the laser wavelength used. Irradiations carried out at the highest laser intensity (1014 W/cm2) and laser pulse count of ≥50 resulted in the creation of crater like damages with depth up to 20 µm. Craters were conically shaped, implying intensive processes which took place at the surface. Generation of LIPSS as well as craters can be of great interest for contemporary technologies.

A study of ASP 30 steel surface modification with high intensity Ti:sapphire laser, operating at 804 nm wavelength and pulse duration of 60 fs, in vacuum ambient, is presented. ASP 30 steel surface variations were studied at laser intensities of 1014 and 1013 W/cm2. The steel target specific surface changes and phenomena observed are: (i) Creation of craters at 1014 W/cm2 intensity; (ii) formation of periodic surface structures only at the reduced intensity of 1013 W/cm2; (iii) chemical surface changes registered only at higher laser intensity, and (iv) occurrence of plasma in front of the surface, including its emission in X-ray region. It can be concluded from this study that the reported laser intensities can effectively be applied for ASP 30 steel surface modification. Careful choosing of laser intensity and pulse count can lead to precise superficial material removal, for example laser intensity ~1013 W/cm2 and low pulse count can lead to ultra-precise surface processing. Generally, femtosecond laser surface modification of ASP 30 steel is non-contact and very rapid compared with traditional modification methods.

No abstract