Mechanical and tribological properties of tricalcium phosphate reinforced with fluorapatite as coating for orthopedic implant Achouak Elghazel a,⇑ , Rym Taktak b,1 , Khaled Elleuch b,2 , Jamel Bouaziz a,3 a Laboratoire de Chimie Industrielle (LCI), Ecole Nationale d’Ingénieurs de Sfax (ENIS), B.P.1173-3038, Université de Sfax, Tunisia b Laboratoire de Génie des Matériaux et Environnement (LGME), Ecole Nationale d’Ingénieurs de Sfax (ENIS), B.P.1173-3038, Université de Sfax, Tunisia article info Article history: Received 12 May 2017 Received in revised form 20 November 2017 Accepted 10 December 2017 Available online 12 December 2017 Keywords: Bioceramics Wear and tribology Mechanical properties Tricalcium phosphate Fluorapatite Alumina abstract In this work, the tribological and mechanical behaviour of tricalcium phosphate-Fluorapatite (b-TCP-Fap) bioceramic was investigated. Indeed, the Fluorapatite was added to the tricalcium phosphate to improve its mechanical properties. The mixture of both powders is considered as a bioactive coating that is likely to be used in orthopaedic implants. The assays were conducted on the cylindrical blocs by compacting the mixture in a metal mould. The characteristics of the specimens were investigated with various methods, including optical microscopy, scanning electron microscopy (SEM), nanoindentation and a ball-disk tri- bometer. The lowest volume wear was measured for b-TCP-26.52%Fap biocomposites under dry condi- tion. Hence, b-TCP-26.52%Fap specimens have revealed the best wear resistance properties. The results would be helpful to fully understand the effect of the addition of the Fluorapatite to b-TCP matrix on its tribological properties. Ó 2017 Elsevier B.V. All rights reserved. 1. Introduction The problem of friction. and wear in the prosthesis for the sub- stitution of hip joints and knees have been addressed by many authors [1–3]. Attention has been drawn to the development of various coatings to supplement the function of the current implants. In the same vein, many researchers have advocated that calcium phosphate ceramics are biocompatible and may develop interactions with human living bone tissues. In the literature, it is well known that the application of monolithic tricalcium phos- phate (b-TCP) at high load bearing conditions is limited due to its brittleness, poor fatigue-resistance and poor mechanical resistance [2]. To overcome this problem, researchers have attempted to syn- thesize b-TCP-based composites with better combination of phys- ical properties than monolithic b-TCP. Thus, Fap has recently been the interest of researchers due to its chemical composition similar to the bone mineral, and therefore its excellent biocompatibility [4]. In fact, the human bone contains about 1 wt% of Fluor that is known as an effective element in caries’ inhibition [4]. It is in this context that the present work lies as an attempt to investigate the tribological behavior of b-TCP-Fap composite coatings. Considering the interesting bioactivity of fluorapatite, however, it is surprising that very limited research works have been conducted on the synthesis and characterization of b-TCP-Fap composite coatings so far. The aim of the current study is to explore the effect of adding fluorapatite (13.26; 19.9; 26.52; 33.16; 40 wt% corresponding to 0.5; 0.75; 1; 1.25 and 1.5 wt%, respectively, of Fluor) to pure b-TCP on fretting corrosion against alumina counterbody. In this work, the fracture toughness, hardness, friction coefficient and the volume wear are presented and discussed. 2. Material and methods The fluorapatite powder was synthesized using a wet-chemical method [4]. A calcium nitrate solution was gradually added to a boiling solution containing di-ammonium hydrogeno-phosphate, and ammonium fluorine solution was added to the mixture in order to adjust the pH to 9. The obtained precipitate was filtered and calcined at 500 °C. The pure commercial tricalcium phosphate powder (Medicoat, 99.3%) was used as base material. The approx- imate Fap-b-TCP representatives were [{13.26 wt%, 86.74 wt%} https://doi.org/10.1016/j.matlet.2017.12.044 0167-577X/Ó 2017 Elsevier B.V. All rights reserved. ⇑ Corresponding author. E-mail address: elgazelachwak@live.fr (A. Elghazel). 1 Wang Q, Ge S and Zhang D. Nano-mechanical properties and biotribological behaviors of nanosized HA/partially stabilizes zirconia composites. Wear 259 (2005) 952–957. 2 Kamar A, Biwas K and Basu B. Fretting wear behavior of Hydroxyapatite – Titanium composites in simulated body fluid supplemented with 5 g l 1 bovine serum albumin. Journal of Physics D: Applied Physics, 46 2013. 3 F. Ben Ayed, J. Bouaziz and K. Bouzouita, (2000), Pressureless sintering of fluorapatite under oxygen atmosphere, Journal of the European Ceramic Society, Vol. 20 (8), 1069–1076. Materials Letters 215 (2018) 53–57 Contents lists available at ScienceDirect Materials Letters journal homepage: www.elsevier.com/locate/mlblue