Modification of multilayered TiAlN/TiN coating by nanosecond and picosecond laser pulses

A multilayered TiAlN/TiN coating deposited on H11 work-steel was irradiated by a TEA CO(2) laser (ns pulses) and a Nd:YAG laser (ps pulses), and the effects compared. The coating was 2.17 mu m thick and consisted of 45 layers. The laser-induced modifications showed dependence on laser pulse duration, pulse count and laser wavelength. The conditions for coating ablation in both cases were determined. The experiment has revealed laser-induced periodic surface structures (LPSS) on nanometre and micrometre scales, depending on the laser wavelength used. Sample surfaces were characterized before and after laser irradiation by an optical microscope, scanning electron microscope (SEM), focused ion beam (FIB) microscope and profilometry

Picosecond laser ablation of nano-sized WTi thin film

Interaction of an Nd:YAG laser, operating at 532 nm wavelength and pulse duration of 40 ps, with tungsten-titanium (WTi) thin film (thickness, 190 nm) deposited on single silicon (100) substrate was studied. Laser fluences of 10.5 and 13.4 J/cm(2) were found to be sufficient for modification of the WTi/silicon target system. The energy absorbed from the Nd:YAG laser beam is partially converted to thermal energy, which generates a series of effects, such as melting, vaporization of the molten material, shock waves, etc. The following WTi/silicon surface morphological changes were observed: (i) ablation of the thin film during the first laser pulse. The boundary of damage area was relatively sharp after action of one pulse whereas it was quite diffuse after irradiation with more than 10 pulses; (ii) appearance of some nano-structures (e.g., nano-ripples) in the irradiated region; (iii) appearance of the micro-cracking. The process of the laser interaction with WTi/silicon target was accompanied by formation of plasma

In situ structural evolution of arc-deposited Cr-based coatings

Cr-based coatings were prepared by cathode arc-evaporation technology using N2 and C2H2 as reactive gases. Three compositions were investigated, Cr60N40, Cr41N27C32 and Cr67C33.The present investigation is centred on the structural stability via coatings tempering up to 1000 °C, by in situ X-ray diffraction in protective atmosphere. As-deposited coatings present low order structure with a medium feature size less then 10 nm. The hexagonal ?-Cr2N phase, characteristic of binary Cr60N40 coating, was stable up to 900 °C, before recrystallization and grain growth takes place. For Cr41N27C32 film the phase transition varies from the metastable ?-Cr(N,C) to orthorhombic chromium carbonitride Cr3(CxN1 ? x)2 phase up to 800 °C and then to chromium carbide phase. No chromium nitride phases were detected in spite of the similar N and C contents after the deposition. The Cr–C coating recrystallizes into a mixture of carbide phases, mainly Cr3C2 and Cr23C6 after 1000 °C annealing treatmen