Composite Polyetheretherketone-Based Coatings on Titanium Alloys

One of the promising ways to improve the surface properties of titanium and its alloys is through the deposition of polymer-based coatings. Polyetheretherketone (PEEK) is one of the representatives of the group of thermoplastic polymers. This high-performance engineering material is characterized by numerous favorable properties, including chemical and dimensional stability, low density, high tensile strength, and excellent wear resistance. PEEK coatings have been demonstrated to exhibit strong adhesion to titanium alloy substrates and improve their resistance to electrochemical corrosion. Therefore, it is a superior material that can be used for the development of advanced composite coatings for a wide range of applications. The necessity to develop composites arises from the limitations of the material, e.g., biological inertness, lack of antimicrobial activity, and relatively high coefficient of friction. To improve existing properties and impart new properties, various additives, such as metals, ceramics, or other polymers, can be added to the PEEK. For biomedical applications, bioactive and antibacterial components are introduced. For tribological applications, it is important to use solid lubricants or those that enhance resistance to frictional wear. Furthermore, the properties of PEEK strongly depend on its structure, which may be amorphous or semi-crystalline. The structure and, therefore, the properties can be modified through heat treatment, chemical treatment, such as sulfonation or fluorination, or a combination of both. One of the dynamically growing routes for developing robust PEEK-based coatings is electrophoretic deposition (EPD) combined with post-heat treatment. The EPD enables the co-deposition of all types of existing materials, while heat treatment densifies the coatings and provides mechanical strength and high adhesion strength. This chapter provides comprehensive information on the latest developments in PEEK-based composite coatings on titanium alloy substrates by EPD and heat treatment, as well as the microstructure and various properties of coated materials. Potential applications and future perspectives are presented.