Abstract
The objective of this review is to present the results on the production techniques, process parameters and compositions of heat-resistant coatings for graphite and carbon-carbon composites. The data reported concern the resistance of such protective coatings in air at temperatures up to 2273 K and in the high-speed flows of oxidizing gas media taking place in the spacecraft equipment. Coatings of this type, generally, have a multilayer structure based on the refractory compounds such as carbides, borides, silicides of transition metals and oxides with a high melting temperature. An efficient heat-resistant coating for carbon-based materials should be composed of three layers from which each fulfills its own function. The paper presents a new complex method for formation of heat-resistant coatings on the carbon-based materials. The method combines the vacuum-activated diffusion saturation in the presence of a liquid-phase and self-propagating high-temperature synthesis (SHS) simultaneously.
Highlights
Graphite and carbon-carbon (C/C) composite materials offer a diversity of unique high-temperature properties that makes them ideal candidates for various high-temperature structural applications, in particular, spacecraft engineering
Under conditions of high temperatures, even above 773 K, C/C composites reveal comparatively low oxidation resistance, which restricts to a great extent their wide application in different fields, in the high-temperature equipment
The effective protection of C/C composites against oxidation can be provided with taking into account the following: use of such materials as oxides, carbides, nitrides, borides, silicides and their various compounds; deposition methods and conditions; thickness and crack resistance of coatings; material designing limiting because of the chemical activity of material reinforcement components; new approaches to the choice of a heat-resistant coating material
Summary
Graphite and carbon-carbon (C/C) composite materials offer a diversity of unique high-temperature properties that makes them ideal candidates for various high-temperature structural applications, in particular, spacecraft engineering. Among different properties of carbon-based materials, the most frequently used are: hardening by heating to ~2773 K, high thermal stability, heat conductivity, and relatively low coefficient of thermal expansion. It should be noted, that C/C composites, compared to graphite, have a higher resistance to thermal and mechan-. The problems of effective protection for carbon-based materials, being under conditions of different oxidizing media, are comprehensively discussed in the literature. In the above-mentioned review, one offers to use for carbon-based material protection the refraction metals such as W, Re, Mo, Nb, Hf, Ti, Zr, their oxides, silicides, borides, carbides, nitrides and composites with these components
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