Abstract
Two aluminide layers (additive and interdiffusion) were deposited on a turbine blade made of ŻS6K superalloy by means of VPA and CVD methods. The additive and interdiffusion layers obtained by the VPA method consist of the NiAl phase and some carbides, while the additive layer deposited by the CVD method consists of the NiAl phase only. The residual stresses in the aluminide coating at the lock, suction side, and pressure side of the blade were tensile. The aluminide coating deposited by the CVD method has an oxidation resistance about 7 times better than that deposited by the VPA method. Al2O3 + HfO2 + NiAl2O4 phases were revealed on the surface of the aluminide coating deposited by the VPA method after 240 h oxidation. Al2O3 + TiO2 oxides were found on the surface of the aluminide coating deposited by the CVD method after 240 h oxidation. Increasing the time of oxidation from 240 to 720 h led to the formation of the NiO oxide on the surface of the coating deposited by the VPA method. Al2O3 oxide is still visible on the surface of the coating deposited by the CVD method. The residual stresses in the aluminide coating after 30 cycles of oxidation at the lock, suction side and pressure side of the turbine blade are compressive.
Highlights
The increasing efficiency of advanced turbine engines requires higher operation temperatures for more complete combustion of fuels
This paper presents the results of the research performed on the aluminide coating deposited by the chemical vapor deposition (CVD) and vapor phase aluminizing (VPA) methods on the turbine blade made of Z_S6K superalloy
The additive and the interdiffusion layers obtained by the VPA method consists of the NiAl phase and some carbides, while the additive layer deposited by the CVD method consist of the NiAl phase only
Summary
The increasing efficiency of advanced turbine engines requires higher operation temperatures for more complete combustion of fuels. At the high working temperature above 1000 °C, surface oxidation becomes the life limiting factor (Ref 1). Aluminide coatings rely on formation of the b-NiAl phase on the surface of the alloys. By which aluminide can be deposited include: pack cementation, vapor phase aluminizing (VPA) and chemical vapor deposition (CVD). The vapor phase is transported to the chamber and reacts with the alloy which forms the aluminide coating. In the vapor phase aluminizing process (VPA), the component to be coated is inside the retort but not in contact with the pack (Al-Cr alloy and Al2O3 filler). The halide vapors are plumbed on to the accessible internal and external surfaces of the component. In the CVD process, the halide vapor sources are external in individual generators and vapors are plumbed on
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