Abstract
Thermal barrier coatings serve as thermal insulation and antioxidants on the surfaces of hot components. Different from the frequent thermal cycles of aero-engines, a heavy-duty gas turbine experiences few thermal cycles and continuously operates with high-temperature gas over 8000 h. Correspondingly, their failure mechanisms are different. The long-term failure mechanisms of the thermal barrier coatings in heavy-duty gas turbines are much more important. In this work, two long-term failure mechanisms are reviewed, i.e., oxidation and diffusion. It is illustrated that the growth of a uniform mixed oxide layer and element diffusion in thermal barrier coatings are responsible for the changes in mechanical performance and failures. Moreover, the oxidation of bond coat and the interdiffusion of alloy elements can affect the distribution of elements in thermal barrier coatings and then change the phase component. In addition, according to the results, it is suggested that suppressing the growth rate of uniform mixed oxide and oxygen diffusion can further prolong the service life of thermal barrier coatings.
Highlights
A heavy-duty gas turbine is an important device for power generation
In the fabrication and service processes of thermal barrier coatings (TBCs), the surface of the bond coat (BC) is inevitably affected by the external and Xu et al [113] considered the stress relaxation induced by creep in a low-melting-point Sn electrode during Li diffusion, the results showed that creep can improve the durability of electrode
Elsass et al [83] investigated coat fabrication processes on the formation of Kirkendall voids, the results showed that compared to the effect of MCrAlY bond coat fabrication processes on the formation of Kirkendall voids, the bond coats sprayed by high-velocity oxygen fuel (HVOF), bond coat fabricated by low pressure plasma results showed that compared to bond coats sprayed by high-velocity oxygen fuel (HVOF), bond spraying (LPPS) has the less Kirkendall voids during the oxidation, and the location of voids changes coat fabricated by low pressure plasma spraying (LPPS) has the less Kirkendall voids during the from bond coat to superalloy substrate
Summary
A heavy-duty gas turbine is an important device for power generation. Thermal barrier coatings (TBCs) serve as a thermal protection structure and protect the hot components in heavy-duty gas turbines [1]. Long-term failure mechanism is helpful for us to the service performance predict the Generally, oxidation and element diffusion areevaluate a continuous and related process and [2]. Oxidation and diffusion, as a whole, are responsible for long-term failure mechanisms of TBCs in heavy-duty gas turbines. Schematic diagram diagram of of oxidation oxidation and and the the diffusion diffusion of of guest guestatoms atomsin inthe thelong-time long-timeservice service process of thermal barrier coatings (TBCs) in heavy-duty gas turbines. Figure diagram of oxidation the diffusion guest atoms in the long-time service process of thermal barrier coatings (TBCs) in heavy-duty gas turbines. To clarify the long-term failure mechanisms of TBCs in heavy-duty gas turbines, in this work, we. To clarify the long-term failure mechanisms of TBCs in heavy-duty gas turbines, in this work, review TGO growth and element diffusion, respectively.
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