Scratch resistance and tribological performance of thermosetting composite powder coatings system: A comparative evaluation Manel Zouari a , Mohamed Kharrat a, ⁎, Maher Dammak a , Massimiliano Barletta b a Laboratory of electromechanical systems, National Engineering School of Sfax, BP 1173, Sfax 3038, Tunisia b Department of Mechanical Engineering, University of Rome Tor Vergata, Rome 00133, Italy abstract article info Article history: Received 25 July 2014 Accepted in revised form 26 December 2014 Available online xxxx Keywords: Wear Scratch Powder coatings Solid lubricant Electrostatic spray The knowledge of the coating properties in terms of scratch and wear resistance is extremely important to prevent severe damage. This paper focused on the study of a comparative evaluation of the scratch and wear per- formance of two thermosetting powder coatings filled with different weight fractions of molybdenum disulfide (MoS 2 ) solid lubricant. Indeed, the thermoset polyester and epoxy organic powder were deposited onto alumi- num substrates by an electrostatic spray coating process. The effect of MoS 2 solid lubricant on the friction and wear behavior of both polyester and epoxy composite powder coatings were assessed via reciprocating tribometer under dry friction conditions. The micro-mechanical performance of the scratch resistance of the composite coatings was conducted using progressive load scratch tests. The experimental findings of the tribo- logical analysis have proven a significant reduction of the friction coefficient and a higher anti-wear ability of the polyester composite coatings compared with the epoxy matrix to which the addition of MoS 2 particles has a little effect on the friction-reducing mechanism. Finally, the investigation of the scratch resistance of the poly- ester or epoxy composite powder coatings filled with MoS 2 confirms that the incorporation of MoS 2 particles to either polyester or epoxy matrices leads to a significant decrease of the critical loads characterizing the coating damage. From the residual depth trends and contact pressure analyses, the epoxy composite coatings reinforced by 5 wt.% of MoS 2 are found to have a great scratch resistance response compared to the polyester composite reinforced by the same wt.% of MoS 2 . © 2015 Elsevier B.V. All rights reserved. 1. Introduction The growing interest in powder coatings has opened new challenges towards the definition of new material formulations, which can im- prove film properties, reduce environmental impact, and, above all, allow energy savings. Compared to metal and ceramic coatings, polymer coatings are generally weak materials that obviously have some limita- tions [1,2]. To overcome such limitations, a number of material- processing strategies have been used to improve the wear and mechan- ical performance of polymer coatings. In recent years, there has been a remarkable growth in the large- scale production of fiber and/or filler reinforced thermosetting matrix composites. Thanks to their high strength and stiffness-to-weight ratios, they are extensively used for a wide variety of structural applications as in aerospace, automotive, and chemical industries [3]. In order to obtain perfect friction and wear properties, many researchers have modified polymers using different fillers [4–10]. When added to polymers, solid lubricants such as graphite and MoS 2 proved to be effective in reducing the friction coefficient and wear rates of composites [11]. The influence of fillers on the polymers of scratch response of polymers has not been completely understood yet. One of the most important functional requirements of organic coat- ings is the adhesion strength, including sufficient cohesion in the bulk and good adhesion to the substrate, which is of great importance in a wide range of manufacturing processes. The polymers scratch resis- tance has been the subject of numerous studies, leading to specific def- initions for plastic deformation characterization and fracture resistance during the scratch testing. Nowadays, polymer coatings have increas- ingly been the interest of many research studies. In fact, the use of poly- mers, in which the coated substrate showed a significant improvement in surface performance, has led to remarkable results. Hence, polymer coatings have increasingly attracted industrial attention, especially in the automotive fields. In many industrial applications, the coating adhe- sive strength is one of the most important parameters. Resistance to scratch is particularly one of the most important features. The perfor- mance of polymer components is greatly influenced by the presence of scratches. Therefore, understanding the polymers scratch behavior is crucial to maintain their good appearance and enhance their durabil- ity, as well. Recently, micro- and nano-scale scratch and indentation tests have largely been used to evaluate the local mechanical performance of polymeric films manufactured by different deposition processes and Surface & Coatings Technology xxx (2015) xxx–xxx ⁎ Corresponding author. Tel.: +216 97 475 845; fax: +216 74 246 347. E-mail address: mohamed.kharrat@ipeis.rnu.tn (M. Kharrat). SCT-20003; No of Pages 9 http://dx.doi.org/10.1016/j.surfcoat.2014.12.066 0257-8972/© 2015 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Surface & Coatings Technology journal homepage: www.elsevier.com/locate/surfcoat Please cite this article as: M. Zouari, et al., Surf. Coat. Technol. (2015), http://dx.doi.org/10.1016/j.surfcoat.2014.12.066