Tribology and Materials Vol. 2, No. 1, 2023, pp. 1-7 ISSN 2812-9717 https://doi.org/10.46793/tribomat.2023.003 1 This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) license Tribological performance of thermal sprayed coatings under abrasive conditions Emmanuel GEORGIOU 1, *, Angelos KOUTSOMICHALIS 1 , Dirk DREES 2 , Christos PANAGOPOULOS 3 1 Hellenic Air Force Academy, Athens, Greece 2 Falex Tribology, Rotselaar, Belgium 3 National Technical University of Athens, Athens, Greece *Corresponding author: emmanouil.georgiou@hafa.haf.gr Keywords thermal spraying coatings abrasion wear friction triboscopy History Received: 16-02-2023 Revised: 16-03-2023 Accepted: 17-03-2023 Abstract In this work, the tribological behaviour of thermally sprayed titanium and chromium ceramic-based coatings was investigated under abrasive conditions. Their structure was studied by a scanning electron microscope (SEM), while their hardness was evaluated using a microhardness tester. To study the strength of these ceramic coatings under abrasion conditions, reciprocating sliding experiments were carried out in a high-precision (10 mN resolution, 1000 Hz data acquisition) pin-on-disk apparatus and by using a Ø 6 mm corundum ball to generate high contact pressures (1.5 GPa). To thoroughly investigate the friction evolution of the tribo-system, three-dimensional mapping of the tangential friction forces (triboscopy) was performed. Following the abrasion experiments, the wear of these coatings was measured using confocal microscopy. The obtained friction and wear results were compared to state-of-the-art materials and coatings that are currently being used in various industrial applications. From this comparison, it was found that the titanium and chromium ceramic-based coatings have comparable if not better tribological properties for the given conditions. The main wear mechanism was mainly two-body abrasion due to the surface roughness of the counter-material, as well as three-body abrasion due to the formation of debris at the interface. 1. Introduction Thermal spraying has been present for more than a century since it was initially introduced in the early 1900s by Dr. Schoop [1]. During this time, it has evolved and improved to deposit a variety of metallic, ceramic, polymeric and composite materials, and is nowadays recognised as a reliable and cost-efficient method for depositing thick coatings onto industrial components [2]. Examples of thermal sprayed coatings can be found in a variety of industrial and technological fields that range from aerospace [3], automotive [4] and biomedical [5] components, up to vital parts in manufacturing processes [6] and energy production [7]. Recently, thermal spraying is also considered a promising alternative to hard chromium coatings [8], in an effort to minimise the negative environmental impact of hard chromium electroplating processes [9]. Among the thermal spraying coatings, ceramic- based are gaining increasing importance as they can successfully protect metallic substrates from wear [10], oxidation [11] and corrosion [12]. However, one of their main drawbacks is that due to their high melting temperature and low thermal expansion (compared to the metallic substrate), they require a bond coating [13]. From the existing oxides, chromium oxide is the hardest and has also been reported to exhibit good frictional properties, high wear, and corrosion resistance [14]. Thus, it is used in tribological and microelectronic applications and as an adiabatic