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This study has been initiated to form a TiO 2 layer having enhanced biological properties on the surface of a CoCr alloy, which is mostly used in manufacturing of orthopaedic implants. As a novel approach, CoCr alloy samples were first coated with titanium and then oxidised in air at 600°C for 60 h. Surface characterisation of the samples were made by structural surveys (scanning electron microscopic examinations, X-ray diffraction analyses), roughness and hardness measurements, bioactivity and wear tests. Results of the experiments have showed that fabrication of TiO 2 as the outermost surface layer caused remarkable increment in the wear resistance and the bioactivity of the CoCr alloy.

In this study, structural characteristics and tribological performance of the coatings deposited on a 1050 quality aluminium substrate by cold spraying of the feedstock consisting of 100% Al-12Si and 25 vol.% SiC + 75 vol.% Al-12Si powders were examined. Wear tests were conducted in air and in water against alumina ball under loads of 1 and 5 N by a reciprocating wear tester at room temperature. Presence of SiC particles in the structure enhanced the wear resistance of the Al-12Si coating both in air and water. As compared to the air testing condition, water containing media provided better tribological performance especially at the wear test load of 1 N. The findings of this study revealed potentiality of water to be used as a lubricant for SiCreinforced Al-12Si matrix cold spray composite coatings at relatively low wear test loads. This is part of a special issue featuring papers based on presentations given at the TurkeyTrib'15 Conference, which have been revised and extended before inclusion in Tribology -Materials, Surfaces & Interfaces.

Micro-arc oxidation (MAO) is an attractive process for the fabrication of protective coatings on aluminum alloys used in many industrial applications, such as automotive, structural and aerospace. However, improvements in the corrosion resistance of aluminum alloys upon covering their surfaces with MAO coating may not be sufficient for extending the service life of the components utilized in harsh environments. In the present study, the MAO coating formed on a 6061 aluminum alloy was sealed using a stearic acid treatment. In the scope of the present study, the surface and cross-sectional microstructures and the phases of the MAO coatings were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques, respectively. The wettability and surface roughness of the samples were measured by goniometer and profilometer, respectively. The corrosion resistance was assessed by long-term immersion in 3.5 % of mass fractions NaCl solution. Finally, it is concluded that sealing of the MAO coating by stearic acid treatment significantly improved the corrosion resistance of the 6061 quality aluminum alloy as compared to the untreated state and the unsealed MAO state. Keywords: aluminum alloy, micro-arc oxidation, ceramic coating, sealing, corrosion.Oksidacija v mikroobloku (MAO) je zanimiv postopek za izdelavo za{~itnih nanosov na aluminijevih zlitinah, ki se jih uporablja v {tevilnih industrijah, kot je avtomobilska, gradbeni{tvo in letalstvo. Vendar pa izbolj{anje korozijske odpornosti aluminijevih zlitin po prekritju z MAO nanosom ni dovolj veliko za podalj{anje zdr`ljivosti komponent, ki se jih uporablja v kislih okoljih. V {tudiji je bila plast MAO, ki je nastala na zlitini aluminija 6061, zatesnjena z obdelavo s stearinsko kislino. V okviru te {tudije, so bile analizirane povr{ine in mikrostrukture preseka in faze v MAO nanosu, s pomo~jo elektronske vrsti~ne mikroskopije (SEM) in z rentgensko difrakcijo (XRD). Omo~ljivost in hrapavost povr{ine vzorcev sta bili izmerjeni z goniometrom in s profilometrom. Korozijska odpornost je bila dolo~ena z dolgotrajnim namakanjem v 3,5 % raztopini NaCl. Ugotovljeno je bilo, da tesnjenje MAO nanosa z obdelavo v stearinski kislini, mo~no izbolj{a korozijsko odpornost aluminijeve zlitine 6061 v primerjavi z neobdelanim stanjem ali z nezatesnjenim MAO.