Scientists at the Ural Federal University (UrFU) and the Institute of Electrophysics of the Ural Branch of the Russian Academy of Sciences have developed a method for synthesizing four-component nanocomposite coatings. It is used to protect gas turbine engines, in aircraft and machine building, for metalworking, and in biomedicine. The new approach does not require high temperatures, additional equipment or materials, and allows to obtain coatings with the required characteristics. The experimental results and description of the method were published in the Membranes journal.
Nanocomposite coatings based on titanium, silicon, carbon, nitrogen are promising for use as protective wear-resistant coatings due to their unique set of properties. Today such four-component coatings are synthesized using a number of physical and chemical methods, but they have disadvantages. And scientists have proposed the method of plasma chemical decomposition, which shows the best results in obtaining the final coatings.
“Compared to the vacuum-arc method, the advantage is the absence of microdroplets that degrade the quality of the coatings. Unlike magnetron sputtering, our method provides higher deposition rates, high ion flux density necessary to form dense and high-quality coatings. If you compare it with the chemical method, the advantage is the use of environmentally and health-friendly, affordable and inexpensive components. The main advantage of the method, in our opinion, is the possibility to independently and within a wide range control almost all synthesis conditions, and, consequently, the composition and properties of the obtained coatings, which makes it possible to obtain films with the required characteristics,” says Andrey Menshakov, researcher at the UrFU and at the Ural Branch of RAS.
The new method is relatively easy to implement: only a gas-discharge device with a hollow cathode and an active anode is used to create a multicomponent active medium. This deposition method does not require separate facilities and ionization and filtration systems because the flow of the evaporated metal does not contain any droplets that disturb the coating structure.
“The nanocomposite structure of such a coating is generally an amorphous matrix with nanocrystals embedded in it. To obtain multicomponent nanocomposite coatings, we use organosilicon precursors - volatile low-toxic liquids containing silicon-carbon and silicon-nitrogen bonds that participate in reactions leading to the formation of the final structure. To synthesize a nanocrystalline phase consisting of crystals titanium-nitrogen, titanium-carbon, or titanium-carbon-nitrogen, we add titanium to the precursor gas environment by its evaporation by electron flow from the plasma. Thus, we create an active vapor-gas environment consisting of the decomposition products of organosilicon molecules and titanium vapor, and the components of this mixture form a coating on the treated surface,” explains Andrey Menshakov.
The researchers note that companies, which have the necessary production technology, are now creating installations for the application of such protective coatings for various enterprises. Using the new method can improve the energy efficiency of existing facilities, as well as the quality of the resulting films. When determining specific requirements for obtaining coatings, for example, on medical products or cutting tools, it is necessary to individually select synthesis conditions that will help to obtain coatings with the necessary characteristics. Now scientists are working on this very task of synthesizing coatings with the required mechanical and physical-chemical properties.
Nanocomposite coatings based on titanium-silicon-carbon-nitrogen began to be produced relatively recently, about 20 years ago. Their physical properties are of particular interest. Their high thermal and oxidation resistance allows them to be used under extreme conditions in aggressive environments, for example, on parts of aircraft or rocket engines. Good anti-friction properties, high hardness and good impact toughness allow using them on cutting tools (cutters, drills, mills, etc.), and high resistance to dust erosion allows using the coating to protect blades of gas turbine engines. They also have good biocompatibility and are suitable for coating medical prostheses and implants.
Synthesis of Nanocomposite TiSiCN Coatings by Titanium Evaporation and Organosilicon Compound Activation in Hollow Cathode Arc Discharge
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