Laser ablation and micropatterning of thin TiN coatings
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Applied Physics A Materials Science & Processing
Laser ablation and micropatterning of thin TiN coatings T.V. Kononenko1 , S.V. Garnov1 , S.M. Pimenov1 , V.I. Konov1 , V. Romano2 , B. Borsos2 , H.P. Weber2 1 General Physics Institute, Vavilov str. 38, 117942 Moscow, Russia 2 University of Bern, Institute of Applied Physics, Sidlerstrasse 5, CH-3012
Bern, Switzerland
Received: 28 July 1999/Accepted: 17 April 2000/Published online: 20 September 2000 – Springer-Verlag 2000
Abstract. Laser ablation of thin TiN films deposited on steel substrates has been studied under wide-range variation of irradiation conditions (pulsewidth, wavelength, energy density and spot size). It has been demonstrated that both picosecond (150–300 ps) and nanosecond (5–9 ns) laser pulses were suitable for controllable ablation and microstructuring of a 1-µmthick TiN film unlike longer 150-ns pulses. The ablation rate was found to be practically independent of the wavelength (270–1078 nm) and pulsewidth (150 ps–9 ns), but it increased substantially when the size of a laser spot was reduced from 15–60 µm to 3 µm. The laser ablation technique was applied to produce microstructures in the thin TiN films consisting of microcraters with a typical size of 3–5 µm in diameter and depth less than 1 µm. Tests of lubricated sliding of the laser-structured TiN films against a steel ball showed that the durability of lubricated sliding increased by 25% as compared to that of the original TiN film. PACS: 42.62.-b; 81.40.Pq; 81.65.Cf Thin-film TiN coatings are widely used in the tooling industry to control the properties of critical components with respect to performance and function. They offer high wear resistance, non-stick properties and low friction. Microstructuring could further improve the friction and wear behavior of such thin film coatings at reduced lubrication level by acting as a lubricant reservoir and maintaining an evenly distributed lubricant film between the friction partners. This new concept in lubricated sliding has been reported in a few recent publications [1–5]. Making fine structures in thin TiN coatings (typically of 1–2 µm thickness) demands the solution of two tasks. First, an applied patterning technique should provide a precise material removal at a micrometer scale, what means that microholes (microgrooves) of several micrometers in size (width) and a depth of less than the coating thickness are to be controllably produced over large surface areas. Second, during structuring the mechanical strength of the coatings should not be lost and such undesirable effects such as the formation of
microcracks and/or a decrease in the coating-to-substrate adhesion should be minimized. These problems can be solved by using a laser ablation technique, the advantages of which for fine surface structuring are generally well established [6– 9]. For each particular patterning application, however, an exact knowledge of the ablation process in dependence on both the laser parameters and material properties is needed in order to determine opti
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