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Zirconium and its alloys are frequently used in many engineering and scientific applications owing to their unique mechanical, chemical and thermal properties. However, zirconium and its alloys may undergo corrosion and wear under some circumstances. Severe operating conditions demand improvement of wear and corrosion resistance of these alloys. In this study, plasma electrolytic oxide coatings were produced on Zr-702 alloy at two different process times then corrosion and wear behaviours of coatings were evaluated. Test results showed that the application of coatings on Zr-702 improved both corrosion and wear resistance remarkably. It has been observed that the coating produced in a longer time exhibited higher load-carrying capacity thus provided better wear resistance than the coating formed in a shorter time. On the other hand, decreasing the PEO process time reduced the structural defects in the coating and led to increased corrosion resistance. [ABSTRACT FROM AUTHOR]

Abstract: In this work, ceramic-like oxide coatings were produced on rare earth element containing Elektron21 (E21) and WE43 Mg alloys using plasma electrolytic oxidation (PEO) process, and in addition to these alloys, AZ31B Mg alloy was used for comparison studies. Surface morphology and chemical composition of coatings were determined using scanning electron microscope (SEM) equipped with energy dispersive X-ray spectrometer (EDS). Phase analysis of coatings was carried out by X-ray diffraction (XRD). Electrochemical corrosion tests were undertaken by means of potentiodynamic polarization and electrochemical impedance spectroscopy techniques in 3.5% NaCl solution at ambient temperature. SEM results showed that the coatings have two layered microstructure with a porous top layer and a dense barrier layer. The SEM images of E21 and WE43 indicated that intermetallic compounds contributed into the coating structure during PEO processing. Electrochemical corrosion test results showed that the corrosion rates of PEO-coated substrates greatly decreased when compared to that of bare Mg alloys. However, bare rare-earth containing alloys showed increased corrosion resistance compared to bare AZ31B alloy. [Copyright &y& Elsevier]

Cold spray (CS) is a solid-state deposition process in which solid powders are accelerated towards the substrate via a converging/diverging nozzle. Coating deposition occurs without melting the sprayed particles. Spray particles adhere to the substrate on impact because of their high kinetic energy. For successful bonding, powder particles have to exceed a critical velocity on impact, which is dependent on the properties of the particular spray material. Different materials such as metals, ceramics, composites and polymers can be deposited using CS. CS is a novel and promising technology to obtain surface coating, offering several technological advantages over thermal spray since it utilizes kinetic energy rather than thermal energy for deposition. As a result, residual stresses, oxidation and undesired chemical reactions can be avoided. Cold spray technology has many applications in the industry. It has been developed for the protection and repair of components used in many industries. In recent years, cold spray process has been used in application fields such as repair of electronic systems, additive manufacturing, welding, brazing, surface protection, medical devices, and medical materials. This study summarizes the cold spray process by briefly reviewing the historical development, basic principles and features, adhesion mechanism and application areas of the cold spray process. [ABSTRACT FROM AUTHOR]