Abstract—The influence of the size and structural elements of GTE and GTU blade model samples on the dendritic structure of a high-temperature ZhS-32 alloy is studied. The sizes of dendrites, γ' phase, and γ/γ' eutectic; the porosity; and the dendritic segregation in castings are estimated using optical and electron microscopy and electron-probe microanalysis. The experimental results indicate that, without a liquid-metal cooler, a structure with the largest sizes of dendrites, γ' phase particles, and γ/γ' eutectic forms in the thick sections of the GTU blade samples. The maximum porosity and dendritic segregation in them are detected. When the temperature gradient in the GTE blade model samples increases (in the case of a liquid-metal cooler), a structure with significantly smaller dendrites and phase particles, lower porosity, and weaker dendritic segregation is found to form in them. The size, design, and method of solidification of the blades is shown to affect the conditions of subsequent heat treatment and gasostatic pressing.

The trends in the development of a technology for the production of the hot gas path parts of a gas turbine engine (GTE) by directional solidification from superalloys are considered. The existing special-purpose equipment used in Russia, the United States, Germany and other countries to produce blades with a directional and single-crystal structure is analyzed. The prospects of directional solidification with a liquid metal cooler in the production of GTE blades for both modern and promising GTEs are clearly demonstrated.

The characteristics of gas turbine engines depend on the structural state of the material of the turbine blades and are largely determined by the technology of their manufacture. Identification of the specific defects of casting is an important goal aimed at improving the quality of blade castings since the castings of turbine blades with a monocrystalline structure made of high-alloyed nickel superalloys (NS) are subject to increased requirements for macro- and microstructure. We present the results of studying the effect of directional crystallization parameters on the morphology of the dendritic structure of NS and their tendency to form casting defects of the single-crystal structure. The structure of alloys in single-crystal blade castings and the effect of technological parameters on the dispersion of the structural components of NS were analyzed upon casting of turbine blades with <001> axial orientation on installations with liquid-metal cooling. It is shown that the parameters of the dendritic cells of castings vary in height from 220 to 330 μg and volume fraction of micropores changes from 0.02 to 0.2%. Electron probe microanalysis revealed that the phase and local elemental compositions of the alloy in the areas of the blade tip and isolated grains are identical. The appearance of isolated grains that violate the monocrystalline structure of castings is observed when the rate of NS cooling decreases. To increase the temperature gradient and reduce the probability of formation of extraneous crystals in castings ahead of the crystallization front, optimized temperature-speed modes of casting and directional crystallization are proposed. The obtained results can be used in the development of temperature-velocity parameters of the process of directional crystallization of blades of promising turbines made of new superalloys.

The scientific, technical, and technological aspects of producing large blades of power gas turbine units (GTUs) are considered. The existing technologies and equipment used in the United States, Germany, and Russia for the production of power turbine blades made of high-temperature alloys with a directional and single-crystal structure are analyzed. The influence of directional solidification methods, the design features of specialized technological equipment, and the GTU blade size on the structural features, the dendrite size, and the porosity and growth defects of the structure is considered. The use of a liquid-metal coolant, namely, the tin melt, during the directional solidification of large GTU blades is concluded to provide the necessary thermal conditions for producing the blades of high-power power turbines.

The results of the development of casting technology for single-crystal high-pressure turbine blades from nickel superalloys with a crystallographic orientation (CGO) [001] were obtained on an automated casting unit for directional crystallization UVNK-9A, at machine-building enterprise. The construction of the casting blades blocks, technologies for the manufacture of molds, rods and casting of GTE working blades of heatresistant nickel alloys with a single-crystal structure and set-up CGO have been developed under real production conditions on UVNK-9A units substituting through-type furnaces. It is shown that preproduction series of single-crystal castings of working blades with shroud shelf were obtained, with a yield of suitable structure ≥ 75%. The structural-phase characteristics of the alloy of single-crystal blades castings were investigated by scanning electron microscopy in as cast state and after subsequent heat treatment. A comparative quantitative analysis of the microstructure and strength characteristics of supernickel alloy castings with CGO [001], obtained on a high-gradient directional crystallization unit and in a through-type furnace.

The effect of the conditions of directed crystallization (the temperature gradient and the crystallization rate) on the dendrite spacing, on the size of the particles of the hardening γ′-phase in the arms and arm spaces of the dendrites, on the volume fraction and size of the pores, on the size of the particles of the eutectic γ/γ′-phase, and on the features of dendritic segregation in a single-crystal castable refractory alloy is studied.

In order to determine the temperature gradients in ingots fabricated by the directional solidification (DS) using an UVNS-6 installation produced by VIAM (Moscow), single-crystalline ingots made of VZhM3 nickel superalloy have been prepared. Herewith, DS technologies with liquid-metal cooling (LMC) and without it are used (the Bridgman–Stockbarger method). A tin melt is used as the LMC. Readings of thermocouples installed on the surface of a ceramic mold are recorded during ingot DS. The DS of ingots made of VZhM3 nickel superalloy using the UVNS-6 installation is simulated in the ProCast program using thermal properties of the alloy, ceramic mold, and parts of the DS installation found in articles, as well as boundary conditions between them (interface heat-transfer coefficients). The good coincidence of the calculated and experimental temperature distributions in the mold during solidification using the Bridgman–Stockbarger and the LMC technique is shown, which makes it possible to use simulation of the ingot fabrication in the ProCast program to predict the temperature gradient at the solidification front, the solidification front profile, and the size of the mushy zone (where the dendritic alloy structure is formed). The temperature gradient attained in the ingot in the case of using the Bridgman–Stockbarger method by the results of simulation was 36°C/cm. The temperature gradient in the case of applying the LMC technique is 204°C/cm; i.e., it turned out sixfold higher than that attained when using the Bridgman–Stockbarger technique. Thermal properties and boundary conditions can be demanded when performing computer simulating of nickel superalloys blade casting process.

Peculiarities of the structure of a refractory eutectic alloy of the Nb – Si system, formed by the method of directed crystallization with liquid-metal coolant, have been studied. Characteristic zones of microstructure of the ingot obtained upon directed crystallization are considered, the alloy composition is analyzed, and volume fractions of phases in the Nb – Si composite are determined.

Directional solidification in a liquid-metal coolant and the formation of a natural composite structure in a eutectic niobium–silicon alloy are studied to produce GTE blades in ceramic molds. The microstructure and the phase composition of the alloy are analyzed in parts of variable sections. The shortand long-term strengths of the niobium–silicon composite material are measured at a temperature of 1200°C.

The results of investigation of the structure of a heat-resistant eutectic niobium–silicon alloy, which was prepared by directional solidification using a liquid-metal coolant, are reported. The typical areas of the macrostructure of an ingot undergone directional solidification are considered, and the composition and the volume fractions of the Nb–Si composite have been determined.

The influence of rare earth metals, such as praseodymium, neodymium, and erbium, and the technology of smelting a nickel aluminide alloy based on “clean” raw materials and using 25, 50, and 75 wt % of waste is investigated. It is found that doping with neodymium and/or erbium in the smelting of structural intermetallic nickel-based alloy increases the heat strength at a temperature of 1200°C and heat resistance at the temperatures of 1100 and 1200°C for 100 h at a weight gain from 1 m 2 . Introducing a different percentage of waste during the smelting the intermetallic alloy results in a slight decrease in the heat resistance but preserves the same level of values when 25, 50, or 75 wt % of waste is included.

The paper presents the research into the conditions of directional solidification with a variable controlled gradient.In