RU2026399C1 - Monocrystal heat-resistant nickel alloy with low density - Google Patents

Abstract

FIELD: metallurgy. SUBSTANCE: alloy has indicated components at the following ratio, wt. -%: cobalt 4.8-7.0; chrome 4.8-7.0; titanium 1.8-4.2; aluminium 5.2-5.8; tungsten 2.0-5.2; molybdenum 1.8-4.2; niobium 0.4-1.0; tantalum 0.001-4.2, and nickel - the rest. Condition: 12.3 ≅ Cr + 0.5 Mo + 0.25 W + Al < 14.7. Alloy provides specific heat-resistance at 1000 C for 500 h σ_sp= 21 - 23·10²m . EFFECT: enhanced quality of alloy. 1 tbl

Description

The invention relates to metallurgy, in particular to finding heat resistant nickel-based alloy for manufacturing single crystal gas turbine parts with operating temperatures up to 1100 ^C, preferably molded with the crystallographic orientation of [001].

Known single-crystal heat-resistant nickel alloys with low (8.4 g / cm ³ ) density, for example: alloy [1] of the following composition, wt.%: Chrome 7.0-13.0 Aluminum 5.0-7.0 Titanium 2, 0-5.0 Cobalt 4.0-16.0 Molybdenum and (or) 1.0-4.0 Rhenium Vanadium 0-2.0 Carbon 0-0.05 Nickel Other alloy [2] of the following composition, wt.% : Chromium 9.5-10.3 Cobalt 4.7-5.3 Molybdenum 2.8-3.2 Aluminum 4.7-4.9 Titanium 4.6-4.8 Tantalum 1.8-2.2 Tungsten 0.1 max Carbon 150 ppm max Boron 50 ppm max Zirconium 100 ppm max Hafnium 0-0.12 Aluminum + titanium 9.3-9.7 Nickel Else
However, these alloys have insufficient specific heat resistance, which is explained by the incompletely compensated chemical composition of the alloys.

Closest to the proposed alloy is a single-crystal, heat-resistant nickel alloy with a low density. Alloy [3] has the following chemical composition, wt.%: Cobalt 5.0-7.0 Tungsten 3.0-5.0 Niobium 0-0.5 Chromium 5.0-10.0 Aluminum 6.0-7, 5 Tantalum 2.0-4.0 Molybdenum 0.5-2.5 Titanium 1.5-2.25 Vanadium 0.3-0.6 Nickel The rest, subject to the ratio
S ₁ = 0.5W + Ta + Mo
S ₂ = Al + Ti + Ta + Nb + V, with 4 ≅ S ₁ ≅ 9, preferably 5.5 ≅ S ₁ ≅ 9 wt.%, 14.9 ≅ S ₂ ≅ 20.6 at.%, Preferably 16.5 ≅ S ₂ ≅ 18.5 at.%.

= 21,18 м. . Однако он не удовлетворяет требованиям по удельной жаропрочности в условиях концентрации напряжений (σ_уд. ^н.), в которых работают реальные изделия (например монокристальная рабочая лопатка) современных ГТД. При этом недостаточный уровень прочностного (K_σ) коэффициента, учитывающего влияние концентрации напряжений на длительную прочность, не позволяет реализовать высокую удельную жаропрочность материала в конструкциях сложной формы с развитой внутренней полостью.This alloy is also used for the manufacture of single-crystal parts of a gas turbine engine and has a higher specific heat resistance. It has the following specific heat resistance at 1000 ^о С for 500 h: σ $\genfrac{}{}{0ex}{}{\text{hl}}{\text{beats}}$ 10 ^-2 =

= 21.18 m. However, it does not satisfy the specific requirements of heat resistance in terms of stress concentration (σ _u. ^N.) In which the real work items (e.g. Mono-Crystal rotor blade) of modern CCD. Moreover, an insufficient level of strength (K _σ ) coefficient, taking into account the effect of stress concentration on long-term strength, does not allow to realize high specific heat resistance of the material in structures of complex shape with a developed internal cavity.

The aim of the invention is to increase the specific heat resistance of the material of products operating in conditions of concentration of stresses while maintaining the level of specific heat resistance. This goal is achieved in that a single-crystal heat-resistant nickel alloy with low density, containing cobalt, chromium, titanium, aluminum, tungsten, molybdenum, niobium, tantalum, according to the invention contains these components in the following ratio, wt.%: Cobalt 4.8-7 Chromium 4.8-7.0 Titanium 1.8-4.2 Aluminum 5.2-5.8 Tungsten 2.0-5.2 Molybdenum 1.8-4.2 Niobium 0.4-1.0 Tantalum 0.001-4.2 Nickel Remaining subject to conditions
12.3 ≅ Cr + 0.5Mo + 0.25W + Al≅ 14.7.

Changing the composition of the alloy and limiting the sum of the elements: both the γ ^I- forming (aluminum) and the elements responsible for the tendency to form topologically close-packed (TPU) phases (chromium, molybdenum, tungsten) under conditions of prolonged use at high temperatures thermal stability of the alloy while regulating its density and maintaining a high hardening effect from the precipitation of the secondary γ ^I phase. Such a positive effect is achieved due to the compensated chemical composition of the alloy, which contributes to the release of γ ^I and γ phases of such compositions in which, firstly, during the long-term action of static loads at high operating temperatures, the solid solution remains stable (without the formation of TPU phases: σ and μ phases), and, secondly, particles of the strengthening γ ^I phase have an optimal cuboid morphology due to the positive mismatch of the lattice parameters of the γ and γ ^I phases.

 Changes in the chemical composition of the alloy and regulation of the total content of these elements are significant, as they are absent in the known technical solutions and give a positive effect.

 In violation of the claimed ratio of elements and non-observance of these conditions, either TPU phases having plate morphology (in the cross section of thin sections-needles) are released, or the specific heat resistance decreases. The alloy in the presence of plates of TPU phases, which are stress concentrators, becomes sensitive to external notches and other stress concentrators, such as, for example, pins, jumpers, and other elements of the internal cavity of a cooled working blade or tooth of a blade lock. In addition, as a result of the diffusion mass transfer occurring in the case of the formation of excess TPU phases during production, the specific heat resistance of the alloy also decreases due to its thermal instability.

 Failure to comply with the ratio between the components can also lead to an increase in the density of the alloy and, as a consequence, to a decrease in its specific heat resistance.

PRI me R. The proposed alloy was smelted in a vacuum induction furnace with a vacuum of 10 ^-2 -10 ^2-3 mm RT. And then smelted in a furnace for directional crystallization using seeds with a crystallographic orientation [001]. Similarly, the prototype alloy was smelted. It was smelted 9 heats and 1 melt alloy prototype. The chemical composition of the swimming trunks and their properties are shown in the table (compositions 1-4 are proposed; compositions 5-9 are beyond; composition 10 is a prototype).

; r - радиус в вершине надреза равен 0,15 мм);
ρ , г/см³ - плотность сплава,
σ_уд ^гл и σ_уд ^н, м - удельная жаропрочность при 1000^оС на базе 500 ч соответственно гладких образцов и образцов с надрезом,
K =

- прочностной коэффициент.The conventions adopted in the table:
S, wt.% = Cr + 0.5Mo + 0.25W + Al;
σ ₅₀₀ ^hl , MPa - ultimate strength of smooth samples on the basis of 500 h at T _test = 1000 ^о С;
σ ₅₀₀ ⁿ , MPa — ultimate strength under similar conditions for testing notched specimens (theoretical stress concentration coefficient α = 3.75; parameters of a V-shaped annular notch: h — notch depth equal to 1 mm; φ — notch opening angle equal to

; r is the radius at the top of the notch is 0.15 mm);
ρ, g / cm ³ - density of the alloy,
σ _bead ^hl and σ _bead ⁿ , m — specific heat resistance at 1000 ^о С on the basis of 500 h, respectively, of smooth and notched specimens,
K =

- strength coefficient.

As follows from the test results shown in the table, the maximum specific heat resistance and heat resistance under stress concentration conditions are achieved only in those cases when the content of alloying elements and the sum S are within the claimed limits (examples 1-4). In this case, there are no needle precipitates of TPU phases, precipitates of the γ ^I phase have cuboid morphology, which, along with the low density of the alloy, leads to its rather high specific heat resistance.

From a comparison of the table it follows that an increase in the level of heat resistance under stress concentration conditions (notched specimens) while maintaining the level of specific heat resistance substantially depends on the sum S: when this amount is exceeded, precipitation of TPU phases (σ, μ phases) is observed in the alloy structure, leading to a decrease in specific heat resistance under stress concentration conditions and a decrease in K _σ (examples 6, 7, and 10); if the sum S has values less than the specified limits, and if S is consistent, the content of the alloying components generally does not match the specified ones, then the specific heat resistance decreases (examples 5, 8 and 9).

 Thus, the proposed alloy has a higher specific heat resistance in the conditions of concentration of stresses and long operating time in the composition of real products of complex configuration. This increase is 7.8-16.4%, which makes it possible to significantly increase the resource of products. Considering that heat-resistant alloys with low density were most effectively used for critical parts of modern and advanced aircraft engines, increasing the specific heat resistance and lowering the sensitivity to stress concentration radically solves the problem of increasing their reliability and resource.

Claims (1)

MONOCRYSTAL HEAT-RESISTANT NICKEL NICKEL ALLOY WITH LOW DENSITY, containing cobalt, chromium, titanium, aluminum, tungsten, molybdenum, niobium, tantalum, characterized in that, in order to increase the specific heat resistance under stress concentration conditions, while maintaining the level of specific heat resistance the alloy contains the following ratio, wt.%:
Cobalt - 4.8 - 7.0
Chrome - 4.8 - 7.0
Titanium - 1.8 - 4.2
Aluminum - 5.2 - 5.8
Tungsten - 2.0 - 5.2
Molybdenum - 1.8 - 4.2
Niobium - 0.4 - 1.0
Tantalum - 0.001 - 4.2
Nickel - Other
and subject to the conditions
12.3 ≅ Cr + 0.5 Mo + 0.25 W + Al≅ 14.7.

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