Coatings of High - Temperature Materials

The properties of materials depend on the characteristics of the bulk and on those of the surf ace. Any change in surface characteristics affects a wide variety of material properties. During the last few years the role of surface phenomena in metallurgy has been the subject of many studies. Surface energy, surface tension, the activity of surfaces, and related problems are under discussion in the western world * as well as in the eastern world. t The relation between volume and surface properties in metals and alloys has been investigated and is still under investigation. Materials are frequently exposed to environments which change their physical and chemical characteristics on account of a reaction going on between the material surface and the environment. The science and technology of surface preparation ro improve material properties have gained importance during the last decade in many parts of the world. Main efforts have been concentrated especially on the coating of material surfaces in connection with the exposure of these materials to space en­ vironment.