Nanocomposite Si3N4/PEEK 708 coatings were successfully fabricated on the Ti-6Al-4V alloy substrate by electrophoretic deposition (EPD) and post-EPD heat treatment. The addition of chitosan polyelectrolyte into ethanolic-based suspensions enabled the cathodic co-deposition of ceramic and polymeric particles. Zeta potential measurements allowed the elaboration of stable suspensions. The selection of the optimal EPD voltage and time enabled uniform coatings to be obtained. Heating above the PEEK melting point and cooling with a furnace or in water resulted in the formation of dense coatings with semi-crystalline or amorphous polymer structures, respectively. Both coatings with a thickness in the range of 90–105 µm had good adhesion and scratch resistance to the substrates, despite the presence of relatively high degrees of open porosity. The coatings improved the tribological properties of the titanium alloy. However, a strong relationship between the polymeric matrix structure and wear resistance was observed. Semi-crystalline coatings proved to be significantly more wear resistant than amorphous ones.

This paper describes ways of improving the tribological properties of the Ti-6Al-4V titanium alloy at room and elevated temperatures by electrophoretic deposition of Al 2 O 3 /PEEK708 composite coatings and postheat treatment. The microstructure of the coating components and the coatings was examined by scanning and transmission electron microscopy as well as x-ray diffractometry. The influence of cooling rate after heating of the coated alloy on the PEEK structure and coating surface topography was investigated. It was found that slow cooling with a furnace produced a semi-crystalline structure, whereas fast cooling in water generated an amorphous polymer structure. The semi-crystalline coatings exhibited a more developed surface topography than the amorphous ones. The coatings with a semi-crystalline structure revealed higher scratch resistance than the amorphous ones. The corrosion resistance of the uncoated and coated specimens was examined using electrochemical techniques in a 3.5 wt.% NaCl aqueous solution. Both coatings increased the corrosion resistance of the alloy. The friction and wear properties of the coated specimens against an alumina ball in dry sliding contact at room temperature and elevated temperatures of 150 and 260°C at ball-on-disk were examined. Both amorphous and semi-crystalline coatings increased the wear resistance and decreased the friction coefficient of the titanium alloy at room temperature. In addition, the semi-crystalline coating was also very effective in improving the titanium alloyÕs tribological properties at elevated temperatures. The obtained results clearly show that the composite alumina/PEEK coatings are promising for tribological applications in mechanical engineering.

In this work, polytetrafluoroethylene/polyetheretherketone (PTFE/PEEK 708) coatings were fabricated by electrophoretic deposition (EPD) and heat treatment to improve the tribological properties of the Ti-6Al-4V alloy. A stable suspension containing chitosan polyelectrolyte allowed the co-deposition of both polymer types. The effect of soaking temperature and cooling rate on the coating microstructure was determined. The homogeneous coatings were obtained by heating at 450°C and cooling with a furnace or in water. The crystalline PTFE separate particles and their agglomerates were homogeneously distributed in a PEEK matrix. Interestingly, the PEEK structure was amorphous regardless of the cooling rate after heating. This new phenomenon is associated with the fluorination process. The coatings exhibited moderate scratch resistance but significantly decreased the coefficient of friction (COF) and enhanced the wear resistance of the alloy during the dry friction process in sliding contact with an Al 2 O 3 ball. The COF of the PTFE/PEEK 708 coating equaled 0.10 at room temperature (RT) and was lower than that of the alloy and pure PEEK 708 coating investigated in the same conditions, which reached 0.70 and 0.27, respectively. The wear rate of the coated alloy at RT was lower than that of the uncoated and PEEK 708 coated alloy, around 1900 and 10 times, respectively. Both the COF and wear increased slightly during friction at 150°C. The coating was not effective in improving the alloy's tribological properties during friction at 260°C.

The present study explores the possibilities of fabricating a graphite/polyetheretherketone (PEEK) composite coating on a Ti-6Al-4V titanium alloy through duplex treatment consisting of electrophoretic deposition (EPD) and heat treatment. It has been found that the electrophoretic co-deposition of graphite and PEEK microparticles can be performed from environmentally-friendly pure ethanolic suspensions. Zeta potential measurements and a study of the interaction between both particle types with the use of transmission electron microscopy allowed potential mechanisms of particle co-deposition to be indicated. Microstructure characterization was performed on macro-, micro- and nanoscale using visible light microscopy, X-ray diffractometry and electron microscopy. This allowed the coating homogeneity and distribution of graphite particles in the polymer matrix to be described. Graphite particles in the form of graphene nanosheet packages were relatively evenly distributed in the coating matrix and oriented parallel to the coating surface. The heat-treated coatings showed high scratch resistance and no adhesive type destruction was observed, but they were highly susceptible to deformation. The corrosion measurements were performed with use of electrochemical techniques like open circuit potential and linear sweep voltamperometry. The coated alloy indicated better electrochemical corrosion resistance compared with the uncoated alloy. This work showed the high versatility of the electrophoretic co-deposition of graphite and PEEK particles, which combined with post-EPD heat treatment allows composite coatings to be fabricated with controlled distribution of graphite particles.

In this work, sulfonated polyetheretherketone (S-PEEK)-based coatings, nanocrystalline ZnS and hydroxyapatite (n-HA) particles were developed on Zr-2.5Nb zirconium alloy substrates by electrophoretic deposition (EPD) combined with subsequent heat treatment. The properties of suspensions and deposition kinetics were studied. Cationic chitosan polyelectrolyte ensured the stabilization of the suspension and allowed for the co-deposition of all coating components on the cathode. The heating of the coated samples at a temperature of 450 °C and slow cooling resulted in sulfonation of the PEEK and the formation of dense coatings. The coatings were characterized by high roughness, hardness, modulus of elasticity and adhesion strength. The coatings revealed mild hydrophilicity, improved the electrochemical corrosion resistance of the alloy and induced the formation of hydroxyapatite with a cauliflower-like morphology on its surface during the Kokubo test. This work explored the great development potential of advanced sulfonated PEEK-based coatings, incorporating antibacterial and bioactive components by EPD combined with heat treatment to stimulate the surface properties of zirconium alloy for prospective dental and orthopedic applications. The antibacterial and osteoconductive properties of the obtained coatings should be further investigated.