Scientists from Skoltech, Tomsk Polytechnic University, and Pirogov Russian National Research Medical University have, for the first time, created multicomponent coatings from high-entropy carbides and carbonitrides using a single-step plasmodynamic synthesis method. Unlike existing methods, the new technique allows for the stable production of a material with a predetermined structure, characterized by high strength and hardness, capable of withstanding elevated temperatures. The results of the work have been presented in the International Journal of Refractory Metals and Hard Materials.
High-entropy carbides are compounds composed of four or more metallic elements. They are extremely strong and possess thermal stability, which is crucial for aerospace technology and other devices operating under extreme conditions. The production of such materials typically involves multiple steps: grinding the raw materials and sintering them with the addition of silicon carbide. This complicates the synthesis process and prevents obtaining a pure final product. Furthermore, finished products often have a wide range of final properties due to impurities in their composition.
The developed method is based on spraying a high-velocity arc plasma jet. To obtain the material using this method, the starting substances are placed into the plasma formation channel; subsequently, under the influence of high temperature, velocity, and pressure, the plasma is deposited onto a copper plate, forming a uniform coating. The entire synthesis process takes place in a gaseous environment.
“This work is a continuation of a series of studies dedicated to high-entropy ceramics. In this research, we applied the plasmodynamic synthesis method, which is entirely new for obtaining coatings of high-entropy ceramics. Due to their unique mechanical properties and stability, the studied high-entropy carbides and carbonitrides can be used as protective coatings in a wide range of applications: in the aerospace industry, energy sector, mechanical engineering, and microelectronics,” shared Alexander Kvashnin, Professor at the Skoltech Materials Center and Head of the Industry-Oriented Materials Discovery Laboratory at Skoltech, a co-author of the work.
“We tested our method by synthesizing multicomponent carbide and carbonitride of titanium, zirconium, niobium, hafnium, and tantalum. Their synthesis was conducted in argon and nitrogen environments. The thickness of the final material, which forms a cubic crystalline phase free of impurities, reaches up to 20 µm. Similar results have been obtained for the first time. The issue is that existing approaches to synthesizing high-entropy carbides and carbonitrides could not yield definitive results due to the complexity of forming multicomponent compounds and the significant variance in the properties of finished products. Our method allows for the deposition of high-entropy ceramic coatings with a stable cubic structure, enabling their comprehensive study,” explained one of the study’s authors, Dmitry Nikitin, Associate Professor at the Electric Power and Electrical Engineering Department of TPU.
The scientists analyzed the resulting composition using X-ray diffractometry and also assessed the mechanical properties and thermal stability of the finished products. The results showed that the hardness of the high-entropy coatings is 32–35 GPa, exceeding the predicted values for materials of similar compositions and surpassing the characteristics of corresponding simple carbides. According to the scientists, samples obtained using the new method also exhibit high oxidation resistance: the coatings retain their crystalline structure at temperatures of 700 °C, making them promising for use in aggressive environments.
The authors note that the proposed method is universal and could potentially be used to synthesize a multitude of new multicomponent carbides with tailored properties. This will allow for the design of ceramic coatings for specific practical tasks — for example, to combat the wear of metal products under extreme temperatures or to enhance their corrosion resistance.
The material is based on a publication by the Ministry of Science and Higher Education of the Russian Federation
