Increase in the refractoriness of carbon composite materials with use of heat-resistant ceramic coatings

Abstract

The main directions are considered for increasing the refractoriness of structural graphite materials, carbon-carbon composite materials (CCCM), and structures made of them. Practical examples are proposed for increasing the refractoriness of materials based on carbon in the application temperature range from 1200 to 1700°C. Results are provided for experimental study of four types of increased refractoriness. It is demonstrated that the contemporary direction of domestic work for increasing the refractoriness of structural graphite materials and CCCM agrees on the whole with a series of overseas achievements in this field.The increase in the cost of industrial energy resources has a marked effect on the cost of a most energy-consuming producing that relates to structural graphite materials, including carbon-carbon composite materials (CCCM). Therefore the task of determining the endurance of these materials during operation acquires even more importance. Graphite materials and CCCM are related to the most heat resistant structural materials, but their refractoriness in oxidizing atmospheres is inadequate.An increase in the operating capacity of structural graphite materials in high-temperature oxidizing atmospheres is the theme of an ever increasing stream of research. A comparatively more complex problem is provision of refractoriness for CCCM in a high-temperature oxidizing atmosphere. This is connected with the more marked difference in thermophysical, elastic and deformation properties of isotropic heat-resistant coatings and anisotropic surface layers for CCCM.The most important problem is increasing refractoriness of graphite materials and CCCM above 1500°C, when structural steels and heat-resistant alloys are not efficient or short-lived. Starting from these temperatures carbon material are oxidized by oxygen, water vapor, carbon dioxide, by a so-called diffusion mechanism [1]. Here reaction with an oxidizing agent proceeds not only over the surface of a component with a specific surface of about 0.5 m 2 /g, but also through the porous volume of a component with a specific surface up to 2 -8 m 2 /g.