Applied Surface Science 257 (2011) 6181–6185 Contents lists available at ScienceDirect Applied Surface Science journal homepage: www.elsevier.com/locate/apsusc TiAlN coatings deposited by triode magnetron sputtering varying the bias voltage D.M. Devia a,b , E. Restrepo-Parra a,∗ , P.J. Arango a , A.P. Tschiptschin c , J.M. Velez b a Laboratorio de Física del Plasma, Universidad Nacional de Colombia Sede Manizales, Cra. 27 No. 64-60, Manizales, Caldas, Colombia b Laboratorio de Materiales, Universidad Nacional de Colombia Sede Medellín, Sede Medellín, Antioquía, Colombia c Escola Politécnica da Universidade de São Paulo, Depto. de Engenharia Metalúrgica e de Materiais, São Paulo, SP, Brazil article info Article history: Received 21 August 2010 Received in revised form 6 February 2011 Accepted 7 February 2011 Available online 2 March 2011 Keywords: Titanium aluminum nitride Crystallography Microstructure Hardness Adhesion abstract TiAlN films were deposited on AISI O1 tool steel using a triode magnetron sputtering system. The bias voltage effect on the composition, thickness, crystallography, microstructure, hardness and adhesion strength was investigated. The coatings thickness and elemental composition analyses were carried out using scanning electron microscopy (SEM) together with energy dispersive X-ray (EDS). The re-sputtering effect due to the high-energy ions bombardment on the film surface influenced the coatings thickness. The films crystallography was investigated using X-ray diffraction characterization. The X-ray diffraction (XRD) data show that TiAlN coatings were crystallized in the cubic NaCl B1 structure, with orientations in the {111}, {200}{220} and {311} crystallographic planes. The surface morphology (roughness and grain size) of TiAlN coatings was investigated by atomic force microscopy (AFM). By increasing the substrate bias voltage from -40 to -150 V, hardness decreased from 32 GPa to 19 GPa. Scratch tester was used for measuring the critical loads and for measuring the adhesion. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Industrial development in the last years has generated several demands in materials technology focused on improving the surface behavior of industrial pieces. Transition metal hard coatings are used to enhance the materials surface properties and to increase their wear and corrosion resistance. Then, carbides, nitrides and boron compounds have been used in the industry [1]. Thin films of transition metal nitrides have been widely studied because of their interesting properties like high hardness, good wear and chemical stability. Nevertheless in the last decades, multi/element nitrides had gained special attention for improving the ternary and qua- ternary nitride properties. One of the most promising thin films is TiAlN, especially because of its oxidation resistance [2], high hard- ness, low friction coefficient, and wear resistance [3]. Moreover, TiAlN is one of the most used coatings applied in dry high speed machining and conforming tools [4]. Physical vapor deposition (PVD) processes are widely used for producing wear and corro- sion resistant coatings on tools or other components [5–7]. One of the most used PVD techniques is sputtering, that has undergone several modifications as the time goes by, with the aim to improve the deposition processes. One of the sputtering technique improve- ments is triode magnetron sputtering (TMS). Compared to diode magnetron sputtering, it offers an enhancement in the ionization ∗ Corresponding author. Tel.: +57 6 8879495; fax: +57 6 8879495. E-mail address: erestrepopa@unal.edu.co (E. Restrepo-Parra). rate by introducing a polarized grid in front of the target. Fontana et al. [8] reported TiN produced by this technique. They found that higher homogeneity results from greater electron collection by the grid. Besides, denser films at lower substrate temperature and com- pact film structure at temperatures of around 300 ◦ C among other characteristics were observed. Although TiAlN films have been pro- duced by several techniques as cathodic pulsed arc [1], magnetron sputtering [9] and laser ablation [10], no works about TiAlN grown by TMS have been reported in the literature. On the other hand, it is well known that physical and chem- ical properties of films growth by magnetron sputtering depend strongly on the processing parameters as pressure, temperature and bias voltage among others. For example, a negative bias volt- age applied to the substrate can significantly improve the ionization and energy of the sputtered particles and enhancing the films crys- tallization. Therefore, the mechanical properties of films may be optimized by adjusting the negative bias voltage [10]. Hsu et al. [11] studied the influence of bias voltage on CrTiAlN coatings deposited on AISI 304 stainless steel substrates. Results showed that the bias voltage increment produces an increase in the Cr concentration, presenting low roughness, high adhesion strength, high hardness, high elastic modulus as well as higher H/E ratio. Benegra et al. [12] have studied the effect of bias voltage on the residual stresses of TiN coatings. Higher compressive residual stress and lower aver- age grain sizes were observed with an increase in the negative bias voltage applied to the substrate. In this work, the study of TiAlN coatings obtained by a triode magnetron sputtering system at different bias voltage is present. 0169-4332/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2011.02.027