PSI - Issue 30

S.P. Yakovleva et al. / Procedia Structural Integrity 30 (2020) 201–208 Yakovleva S. P. t l. / Structural Integrity Procedia 00 (2020) 0 –0 0

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Fig. 1. The destruction of parts of hot path of the gas-driven turbines: a - fragments of the heat insert; b – the crack (showed by an arrow) in the root of the working blade #1; c - the break of the working blade #2 feather (a short arrow points the crack, a long arrow points the trace of a blow by fragments of the neighboring blade) 3. Results and discussion 3.1. Heat-resistant nickel alloys. The operational performance of power plants are largely determined by the properties of heat-resistant nickel alloys which are the main material for the manufacture of thermally stressed elements. These alloys are multicomponent solid solutions based on nickel with an irregular face-centered cube (FCC) of the crystal structure strengthened by dispersed releases of proeutectoid constituent: intermetallides, carbides, borides as pointed by Bernshtein and Rakhshtadt (1985), Sims et al. (1987), Logunov et al. (2019). The main strengthening γ '-phase is an alloyed solid solution based on Ni 3 Al intermetallide with an ordered FCC crystal structure. One of the main requirements for heat-resistant alloys is a resistance to the softening processes which ensures structural stability and constancy of material properties during long-term operation in high-temperature conditions by Kleshev et al. (1995), Xia et al. (2007), Liu et al. (2017). It should be noted here that the reasons for the softening of complex alloys remain insufficiently studied. In this paper, the material of the heat insert of a gas turbine, the operating conditions of which led to changes that caused irreversible deformation of this structural element, are studied. As it was already noted, the working blades, simultaneously exposed to corrosive gas flows, high temperatures and cyclic stresses are more loaded. The studied working blades made it possible to study different stages in the development of processes of the material softening, degradation and destruction: blade #1 is at the stage of crack propagation, blade #2 has already undergone complete destruction. 3.2. The destruction of a heat insert in the combustion chamber of a gas turbine unit . A spectral analysis of the destructed heat insert material was conducted. As a sample of the most appropriate to the initial state of a heat insert, a section was cut from its fixing point, where the overheating is less significant due to the abstract of heat into the surrounding metal body (conventionally "original" sample). The results of the spectral analysis are presented in Table 1, where the standard composition of the HN60VT alloy is given for comparison, which is most often used for manufacturing gas turbine sheet elements. There is a correspondence in the contents of such alloying elements as manganese, silicon, chromium, iron and aluminum. At the same time, there is no tungsten