Abstract
Gas turbines and their blades in particular might be damaged in the course of the aviation turbojet engine operation process. The degradation process of the blade microstructure is most evident from the change in the colour of its surface. This is assessed using the optoelectronic method. The article presents the concept of non-destructive methods, which are used to assess the degree of degradation of the alloy of a gas turbine blade. The proposed optoelectronic method is the basic method for the preliminary determination of color changes in the surface. Appropriate videoscopes or video-analyzers, capable of recording a test object in various electromagnetic wave ranges (infrared radiation, visible range), are used for this purpose. These preliminary results of the diagnosis make it possible to infer further studies of the blade. For accurate investigation of the state of the alloy microstructure, a non-destructive thermographic method (xenon flash pulsed thermography) was used. The results of studies of the degradation of the microstructure with the use of non-destructive methods were verified through the use of metallographic investigations. Appropriate metallographic specimens were created in order to recognize phase γ′ degradation (i.e., the phase strengthening the blade alloy). The results of the presented research allowed for an in-depth assessment of the degree of microstructure degradation of operated blades.
Highlights
The technical condition of turbine blades in the operating process of aviation turbojet engines is of decisive importance for the reliability and durability of a turbine and the entire engine [1,2]
A blade be recorded with a light-sensitive to a secondary light reflected by itssurface surfacemay
Showing the relationshipdetector betweenthanks the surface colour changes, source reflected by its surface
Summary
The technical condition of turbine blades in the operating process of aviation turbojet engines is of decisive importance for the reliability and durability of a turbine and the entire engine [1,2]. The main reason gas turbine blades get damaged is overheating of their material as well as thermal fatigue [3,4,5]. This is caused by adverse operating conditions or manufacturing defects. Important factors causing turbine blade damage are: Insufficiently strong superalloys and protective coatings applied to the blade (vanes), and the use of fuel with decreased quality requirements. The most important factors are complex conditions of mechanical and thermal loads in the course of turbine operation. Exceeding the permissible flue gas temperature, especially over a long operation period, as well as disturbances in or lack of sufficient cooling of turbine blades are dangerous
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