IMPROVING THE THERMAL STABILITY OF CARBON-CARBON COMPOSITE MATERIALS USING SELF-PROPAGATINGHIGH-TEMPERATURE SYNTHESIS

Abstract

Abstract.This research focuses on the development of effective protective coatings for carbon-carbon composite materials (CCСM), which are important components in high-temperature processes in aerospace engineering. The application of CCСM is limited by their sensitivity to oxidation, erosion and burnout in gas streams. In light of these limitations, our work is aimed at creating protective coatings using the method of self-propagating high-temperature synthesis, which provide increased performance and extend the service life of composites. The main task of the research is to identify the optimal compositions of powders for chromium-doped protective coatings through the SHS process. Various methods of obtaining protective coatings were analyzed, including chemical-thermal methods and methods of saturation from the liquid phase, revealing the peculiarities of the interaction of coatings with the CCСM matrix and changes in their mechanical characteristics. In addition to the classical methods of obtaining coatings, the method of surface saturation from the solid phase in an active gas environment as part of the SHS process was investigated. This method provides high-quality coating surfaces, reduction of processing time and the possibility of reaching high temperatures, depending on the composition of the SHS mixture. An important element of the research is the analysis of modern publications and research in the field of protective coatings. Special attention is paid to the problems associated with chemical interaction with the matrix of CCСM and uneven formation of carbide phases along the cross-section of the material. Experimental studies include a factorial experiment to identify the compositions of powder mixtures that provide high wear resistance. Various independent variables, such as chromium, silicon, titanium and aluminum content, are considered for their effect on the physical and mechanical properties of the coatings. The study focuses on the optimization of the parameters of thermal autoinitiation of SHS mixtures under process conditions. The regression equation for evaluating the dependences of the wear resistance of coatings on auto-initiation parameters and the content of alloying elements is given. The analysis of the research results includes the construction of three-dimensional graphic dependencies to optimize the wear resistance of coatings in the Cr-Al-Ti and Cr-Al-Si systems. Chromoalumosilicization of the coating showed better wear resistance, exceeding the wear resistance of untreated samples by 2.6-3.2 times, which allows the use of this technology for parts of aerospace equipment. It is interesting that the porous surface of coatings obtained by the SHS method prevents the penetration of oxygen into the material, contributing to the formation of oxide protective membranes, such as SiO2, TiO2, Cr2O3, Al2O3.