STUDY OF THE PHASES OF ACICULA (LAMELLAR) MORPHOLOGY IN THE MATERIAL OF TURBINE BLADES OF GAS TURBINE ENGINES

Abstract

We present the results of studying features of separating phases of acicular (lamellar) morphology in the structure of blade material of operating gas turbine engines (GTD). A decrease in the strength characteristics and plasticity of the blade feather material in the zone of phase separation which contributes to in-service fatigue destruction of the turbine blade is revealed and illustrated with a specific example. Separation of the phases of needle (lamellar) morphology can be considered a criterion for the quality control of the structure and performance of the turbine blade material which requires appropriate rating. Difficulties in revealing the identification differences in the topologically close-packed (TCP) phases and carbides of Me6C type with acicular (lamellar) morphology are noted. A tend of a heat-resistant alloy to form σ-phase (i.e., the serviceability of the alloy) can be estimated in calculation of the chemical composition from the number of electron vacancies. At the same time, detection and rejection of the blades with inadmissible discharge of σ-phases can be done methods of direct non-destructive control. We develop a method of non-destructive electromagnetic control of TCP-phase (of σ-type) present in the structure of the material of highly oxidized blades (also with extraneous ferromagnetic particles present in internal cavities. Timely detection of σ-phases present in the structure of blade materials upon manufacture or repair will eliminate using the blades with reduced strength and plastic characteristics in GTE.