Nauka i Tehnika (May 2015)
DEVELOPMENT OF TECHNOLOGY FOR APPLICATION OF PLASMA COMPOSITE COATINGS BASED ON ZIRCONIUM DIOXIDE FOR SPACECRAFT SYSTEMS
Abstract
The paper presents investigation results pertaining to the influence of such parameters as plasma jet (current, spraying distance, expenditure of plasma-forming gas – nitrogen), fraction composition of an initial powder and cooling rate with compressed air on characteristics of anti-meteoritic coatings. Due to simplicity of the apparatus design and its tangible efficiency a method of plasma spraying in aerial environment is mainly used presently for application of ceramic layer on the basis of partial stabilized zirconium dioxide. The main peculiar feature of plasma anti-meteoritic coating structure is formation of some controlled porosity in order to increase permissible deformations in ceramics. The idea to create structures with controlled porosity is based on the fact that porous bodies are less liable to macroscopic scattering of cracks under the action of internal stresses due to slowing-down or deviation of an extending crack by pores and also due to low elasticity modulus of porous materials in comparison with compact ones.Methodology of the executed research works has been based on complex metallographic, X-ray and electronic and microscopic investigations of anti-meteoritic coatings on the basis of zirconium dioxide.In order to ensure high impact strength the structure of anti-meteoritic coatings on the basis of zirconium dioxide should contain more than 90 % of tetragonal phase of zirconium dioxide and not less than 10 % of monoclinic phase. In this case phase composition and impact strength of coatings depend on chemical composition and production method of the powder. Optimization of parameters for spraying anti-meteoritic coatings based on zirconium dioxide has been carried out according to obtaining maximum coefficient of material usage and maximum content of tetragonal phase of zirconium dioxide in the sprayed coatings.
