Surface density of growth defects in different PVD hard coatings prepared by sputtering P. Panjan a, * , M.  Cekada a , M. Panjan a , D. Kek-Merl a , F. Zupani  c b , L.  Curkovi  c c , S. Paskvale a a Jo zef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia b University of Maribor, Faculty of Mechanical Engineering, Smetanova 17, 2000 Maribor, Slovenia c Faculty of Mechanical Engineering and Naval Architecture, Zagreb, Croatia Keywords: PVD coatings Defects abstract Growth defects are present in all PVD hard coatings. They have detrimental influence on their tribo- logical properties (higher sticking of workpiece material, higher friction coefficient, worse corrosion resistance, higher gas permeation). In order to improve the tribological properties of PVD hard coatings it is important to minimize the concentration of growth defects. Conventional TiAlN single layer as well as AlTiN/TiN and TiAlN/CrN nanolayer coatings were deposited on cemented carbide, powder metallurgical high speed steel (ASP30) and cold work tool steel (D2) by magnetron sputtering in the CC800/7 and CC800/9 sinOx ML (CemeCon) deposition systems, respectively. The surface morphology of the coated substrates was examined by scanning electron microscope (FE-SEM) in combination with focused ion beam (FIB), and 3D stylus profilometer. By means of 3D-profilometry we performed several measure- ments and detailed analysis on a series of samples from the several hundred production batches. The influence of growth defects on GDOES (glow-discharge optical emission spectrometry) depth resolution and pitting corrosion was also studied. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Coated surfaces contain sporadic defects such as peaks and craters. Growth defects are inherent also in PVD hard coatings. The defect density can be reduced by proper substrate pretreatment and selection of optimal deposition parameters, however, it is difficult to eliminate them completely. The most common type of growth defects is nodular defects. The origin of such defects is irregularities on the substrate surface larger than 0.1 mm (asperities, micro- scratces, inclusions, impurities) and especially the submicrometer sized particles which remain on the surface after the cleaning procedure or those which are generated during coating process. Such small particles nucleate the defects when the surface is coated. The formation of nodular defects in PVD coatings is caused by shadowing effects initiated by seed particles or asperities on substrate surface during the deposition process because evapora- tion and sputtering are line-of-sight processes [1]. At the defect nucleation sites an accelerated growth relative to the matrix growth occurs. The diameter of the nodule, which is conical or parabolic in shape (depending on the flux distribution of the incoming species), increases with the coating thickness. In order to obtain a smooth coating we have to eliminate particles in the production environment. To approach this goal various measures can be taken [2]. The most important one is a high-quality substrate cleaning procedure. The deposition system is also a strong generator of small particles which could contaminate the growing coating. Namely, coating is deposited also on the substrate holders, shields and on other parts at the inner wall of the vacuum chamber and after some deposition time this coating can be delaminated from the surface by stress release (thermal stress, internal compressive stress). The chips are transferred to the substrate surface and incorporated in the growing film. They are held to the substrate by electrostatic forces, which are much stronger than the gravitational forces on micrometer sized particles. From this point of view a periodical cleaning of all components in the vacuum chamber is very important. The thickness of the deposit on inner parts of the vacuum chamber must be minimized in order to avoid the fracture of the stressed coatings. It is also important to avoid any turbulence in the gas flow, thus slow pumpdown and venting must be used. Additional problems are the wear particles from moving surfaces in contact. The concentration of such particles can be reduced if the moving components of the vacuum chamber are made of nongalling materials. Proper design of the fixturing holders is also very important - face upward mounting of substrates should be avoided. The angular distribution * Corresponding author. E-mail address: peter.panjan@ijs.si (P. Panjan). Contents lists available at ScienceDirect Vacuum journal homepage: www.elsevier.com/locate/vacuum 0042-207X/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.vacuum.2011.07.013 Vacuum 86 (2012) 794e798