Reasons for the appearance of defects in the sealing units of the flow-through section of aviational turboprop engines and turbojet engines with the use of cermet materials
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Ni-Si-C cermet materials, during the working process, undergo significant physical and chemical changes under the effect of a gas flow with high parameters. In view of its large excess of air, the gas stream has a high oxidation potentialα = 4–5). The changes observed are exhibited in the burning-out of the graphite (the solid lubricant), in a loss of antifriction properties, as well as in the development of additional porosity.
The process of the oxidation of the metallic matrix develops along the defective sections (the boundaries of the sintered particles, the pores, friable sections). As a result, there takes place a weakening of the metallic contact between the grains and a loss of ductility.
Ni-Si-C cerment inserts, in operation, are under the action of compressive and bending forces, developing as a result of warping of the ring of the jet apparatus, the variable operating conditions, vibration, and the dynamic pressure of the elastic gas stream. In the sealing material itself, there develop local stresses, under the action of forming oxides, phase transformations, and of a difference in the coefficients of linear expansion.
The observed physical and chemical changes in Brand S-137 sealing material, taking account of the effect on it of a complicated complex of working parameters, have made it possible to discover the reasons for the appearance and development of the defects of Ni-Si-C materials most frequently encountered in operation.
KeywordsDuctility Linear Expansion Solid Lubricant Metallic Matrix Metallic Contact
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- 1.M. E. Belitskii and I. F. Skopenko, “Investigation of the operating characteristics of Brand S-5 sealing material, and of the stages of an aviation gas turbine,” Sb. Nauchn. Tr., No. 3, Kiev (1966).Google Scholar
- 2.M. E. Belitskii, I. F. Skopenko, et al., Aviatsionnaya Promyshlennost', No. 1 (1967).Google Scholar
- 3.Physicochemical Properties of the Elements [in Russian], G. V. Samsonova (editor), Kiev (1965).Google Scholar
- 4.B. I. Kostetskii and I. G. Nosovskii, in: Wear Resistance and Antifriction Properties of Machine Parts [in Russian], Kiev (1965).Google Scholar
- 5.Encyclopedia of Metallophysics [in Russian], G. Mazinga (editor), Moscow (1937).Google Scholar
- 6.Ya. E. Geguzin, Macroscopic Defects in Metals [in Russian], Moscow (1962).Google Scholar
- 7.Atomic Mechanism of Failure [in Russian], Collection of articles, Moscow (1963).Google Scholar