TSU Faculty of Physics and Technology scientists are synthesizing a high-entropy alloy of the Hf-C-N-Me-B system that is unique in composition. Their study will gain fundamental knowledge about the properties of such compounds, including at ultra-high temperatures above 4,200 °C. This temperature resistance is one of the key requirements for materials used in aerospace.
The demand for durable materials with ultra-high melting points is growing with the development of technology. Therefore, more and more attention is paid to highly entropic alloys with their unique physical and mechanical properties. Multicomponent alloying is now widely used in world industry, in the production of materials for operation in extreme conditions, This makes it possible to expand the fields of application of modern metallic materials, but in such alloys, it is important to choose the right elements to form a structure with the required characteristics.
- We decided to focus on obtaining heat-resistant materials and refractory coatings. Alloys based on a hafnium compound (Hf) have a high melting point, over 4,200 °C. Therefore, we took the Hf-CN system as a basis and added two components to it: a secondary metal (Me) and boron (B), which, presumably, will contribute to the achievement of high mechanical properties and an increase in the heat resistance of the alloy in oxidizing environments, - said Nikolay Evseev, associate professor in the TSU Department of Applied Aeromechanics.
He added that now it is still difficult to accurately predict exactly how the properties of the alloy will change relative to the sample of the Hf-C-N system, but it is obvious that the result will be a unique material that needs to be carefully studied.
The production of such materials is one of the key challenges for the aerospace industry, where high-temperature resistance is one of the key requirements. The main thermal and mechanical loads are on the front of missiles, jet engines, and aircraft wings. This is especially true for aircraft, which are designed for multiple flights. Indeed, when leaving and re-entering the atmosphere, the temperature can reach 2,000 °C to 4,000 °C.
- The process of synthesizing the alloy itself is quite painstaking, laborious, and unpredictable. It all starts with the preparation of a mixture of initial powders. Then the mixture is placed in a high-pressure reactor, the mixture is ignited and a new alloy is formed as a result of self-propagating high-temperature synthesis, - Nikolay Evseev explained.
The appearance of such alloys back in 2015 was predicted by researchers from the United States. They found that a material based on hafnium, carbon, and nitrogen (Hf-C-N) would have a melting point of over 4,200 °C. In 2019, a team of Russian scientists (MISiS) managed to synthesize a type of hafnium carbonitride with the chemical formula HfC0.5N0.35, the melting point of which turned out to be above 4,200 °C. The task of TSU scientists is to obtain an alloy of the unique Hf-C-N-Me-B system with an extreme melting point and to study its structure and physical and mechanical properties.