FSUE “VIAM”, Moscow, Russia:

E. I. Yakovlev, Leading engineer, e-mail: y-e-i@yandex.ru

PC “ODK-Saturn”, Rybinsk, Russia:
A. I. Berestevich, Сhief metallurg
S. B. Zhabrev, Leading engineer

A new method of casting large-sized cooled blades with a homogeneous, equiaxed grains structure was developed on the basis of the thermophysical analysis carried out. The ranges of porosity and sizes of macro-grains in the structure of the feather and lock of large-sized blades of domestic production are determined. Due to the negative influence of a high porosity level and coarse grain structure on the service properties of the alloy used for blade production, the leading foreign enterprises use the technology that enables to significantly reduce the porosity and size of the macro-grains of the blade castings. The technology used at domestic enterprises cannot provide sufficiently high temperature of the ceramic shell mold prior to pouring stage, which necessitates an increase in the pouring temperature of the alloy in order to enhance the fillability of thin-walled sections of the feather of the blades. This in turn causes the coarsening of the macrostructure of the casting. It is shown that solidification time of the thin-walled sections of feather of the cooled blades significantly increases with an increase in the preheating temperature of the ceramic mold before the melt is poured. The application of surface modification allows refining the macrostructure of thin sections of the feather, which increases its service characteristics, especially the resistance to thermal fatigue loads. At the same time, this modifier is ineffective for such massive casting sections as the lock and the lock shelf of large-sized blades of gas turbine plants. The effect of mold preheating before casting, the temperature of the melt overheating and the pouring temperature on the porosity level, and the macrostructure during casting large-sized blades of gas turbine devices was studied. Based on the results of the experiments, a fundamentally new casting method using a two-stage casting of corrosion-resistant high-temperature alloys TsNK-7P, ChS88U-VI and IN738LC was developed. Cooling rates for the formation of the homogeneous microstructure of blades from corrosion-resistant high-temperature alloys TsNK-7P, ChS88U-VI and IN738LC are specified.

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