Ablation of carbide materials with femtosecond pulses Gabriel Dumitru a,* , Valerio Romano a , Heinz P. Weber a , Marc Sentis b , Wladimir Marine b a Institute of Applied Physics, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland b Groupement Interdisciplinaire Ablation Laser et Applications, LP3 FRE2165 CNRSÐUniversite ÂdelaMe Âditerrane Âe, GPEC UMR 6631 CNRS, Faculte  des Sciences de Luminy, Case 917, 13288 Marseille, France Received 25 March 2002; received in revised form 12 August 2002; accepted 12 August 2002 Abstract The response of cemented tungsten carbide and of titanium carbonitridewas investigated with respect to damage and ablation properties, under interaction with ultrashort laser pulses. These carbide materials present high microhardness and are of signi®cant interest for tribological applications. The experiments were carried out in air with a commercial Ti:sapphire laser at energy densities on the target up to 6.5 J/cm 2 . The irradiated target surfaces were analyzed with optical, SEM and AFM techniques and the damage and ablation threshold values were determined using the measured spot diameters and the calculated incident energy density distributions. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Carbide materials; Femtosecond laser ablation; Abrasive wear; Microstructures 1. Introduction It is generally acknowledged [1] that precise laser microstructuring of gliding surfaces, as well as the use [2] of hard surfaces improve the friction behavior and the wear resistance of tribological systems. The ben- e®cial effects of these approaches can be combined: results on microstructuring of hard coatings using nanosecond and picosecond lasers were reported by us [3] and by other authors [4,5]; there remained, however, some undesired side effects, correlated with the duration of the used laser pulses. Experiments carried out with ultrashort (100 fs) laser pulses are described in this work. Some topics related to the correlation between surface hardness and wear resistance are exposed in the beginning and subsequently the positive role of surface microstruc- turing is discussed. In the following sections the target materialsandsomeoftheirrelevantproperties,aswell as the set-up and the performed experiments are exposed. The analysis of the irradiated spots is described and considerations about thresholds and the morphology changes are also presented. 2. Wear mechanisms Two complementary aspects are usually differen- tiated in tribology: the friction effects, occurring from tangential forces transmitted across the contact sur- face of two solids and the wear phenomena, deriving from the material removal from the contact surface of Applied Surface Science 205 (2003) 80±85 * Corresponding author. Tel.: 41-31-631-8940; fax: 41-31-631-3765. E-mail address: dumitru@iap.unibe.ch (G. Dumitru). 0169-4332/02/$ ± see front matter # 2002 Elsevier Science B.V. All rights reserved. PII:S0169-4332(02)00906-6