Experimental studies of the influence of the characteristics of the metal bond coat on the durability of the heat-protective coating of the turbine blades of a gas turbine engine

The service life of gas turbine engine (GTE) turbine blades with thermal barrier coatings (TBC) depends on many factors, including the composition, structure and properties of the metal bond coating (MB). The positive effect of using TBC is well known: an increase in the service life of the protected part or an increase in the working gas temperature in front of the engine turbine. At the same time, it is also obvious that the development and implementation of new TBCs that use more efficient TBCs is an urgent task. The efficiency and service life of TBCs are significantly affected by the following characteristics of the metal bond coat: material, its thickness and microstructure, and application method. In order to select a rational metal bond coat of the TBC and to assess its performance on turbine blades at high temperatures, a comparative analysis of the isothermal heat resistance of TBCs with different versions of metal bond coats and at different operating temperatures was performed. The time , up to which the total area of ceramic layer chips on the leading edge and trough does not exceed 30%, was adopted as the isothermal heat resistance criterion. Tests of GTE process blades made of ZhS32VI alloy with TBCs with various metal bond coats applied to them using serial technology were carried out at temperatures of 1100 °C and 1170 °C. The isothermal heat resistance test base was at least 500 hours. Four process blades with each of the studied coating options were tested. Analysis of the obtained test results showed that TBCs with a NiCrTaY and AZh-8+CrAl sublayer have higher durability indicators. This effect is due to the presence of refractory elements (tantalum and yttrium) in the MB, which create a diffusion barrier and slow down the growth of the Al₂O₃ oxide film formed on the metal layer. During the experimental studies it was established that the composition of the metal bond coat in the TBC design significantly affects its durability. Thus, the absolute values of  can differ several times. With an increase in the temperature of isothermal tests, a significant (2–3 times) decrease in the durability of the coating is observed. Therefore, the correct choice of the MB composition allows you to reduce the level of stress-strain state at the boundary of the layers, increase the adhesion strength, and thereby increase the durability of the TBC.

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