RU2626118C2 - Casting heat resistant nickel-based alloy - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to casting heat-resistant nickel-based alloys used for the manufacture of high-loaded parts of gas turbine engines and plants, namely, working and nozzle blades of gas turbines with a directional columnar and single crystal structure operating at the temperatures of 1000°C and higher. Casting heat-resistant nickel-based alloy contains, wt %: chromium 4.0-9.0; cobalt 9.0-14.0; tungsten 7.0-10.0; molybdenum 1.0-5.0; aluminium 4.0-6.0; tantalum 6.0-10.0; hafnium 0.1-1.0; carbon 0.002-0.1; yttrium 0.001-0.1; lanthanum 0.001-0.1; cerium 0.001-0.1; silicon 0.01-0.2; manganese 0.01-0.3; boron 0.005-0.03; scandium 0.0002-0.01; nickel - the rest.

EFFECT: specific gravity of the alloy decreases while maintaining a high level of heat resistance.

3 tbl, 1 ex

Description

The invention relates to the field of metallurgy, in particular to cast nickel-based heat-resistant alloys used for the manufacture of highly loaded parts of gas turbine engines and plants, namely, working and nozzle blades of gas turbines with directional columnar and single-crystal structure, operating at temperatures of 1000 ° C and above.

The development of heat-resistant nickel alloys with a single crystal structure used for the manufacture of working and nozzle blades of gas turbines is a leading direction that provides a significant increase in the parameters and reliability of modern gas turbine engines.

The achieved increase in heat-resistant properties is ensured by improving the theory of alloying, including the introduction of relatively new elements such as Ta and Re into alloy compositions. These elements, having a high melting point and low diffusion mobility, provide:

- a marked increase in the strength of interatomic bonds;

- a significant increase in creep strain resistance and the occurrence of stable cracks;

- a significant improvement in structural stability.

), содержащий 4% рения (Re) и 4% тантала (Та), не имевший на тот период аналогов ни в РФ, ни за рубежом, за сравнительно короткое время нашел широкое применение во многих газотурбинных двигателях IV поколения и сегодня является одним из наиболее востребованных материалов.The first domestic alloy of this group is ZhS32 (ρ = 8.76 g / cm ³ ,

), containing 4% rhenium (Re) and 4% tantalum (Ta), which had no analogues at that time either in the Russian Federation or abroad, for a relatively short time has been widely used in many IV generation gas turbine engines and today is one of the most demanded materials.

However, the use of this alloy is simultaneously associated with a serious problem - the cost of rhenium, which has risen significantly in recent decades, which has now reached 5-8 103 USD / kg, as a result, this alloy turned out to be very expensive, which significantly narrowed the possibilities of its use. The cost of the charge of this alloy in the current period is 17.8 million rubles / t, while the cost of alloying elements of the previous generation alloy ZhS6U without rhenium is 2.2 million rubles / t, i.e. 8 times smaller.

Known casting heat-resistant alloy based on Nickel, intended for casting parts by directional crystallization, having the following composition, wt.%:

carbon 0.08-0.2 chromium 4.0-6.0 cobalt 8.0-10.0 tungsten 7.0-10.0 molybdenum 0.5-2.0 aluminum 5.0-7.0 rhenium 3.0-5.0 tantalum 3.0-5.0 boron 0.005-0.03 vanadium 0.01-0.15 cerium 0.001-0.04 yttrium 0.003-0.04 lanthanum 0.001-0.1 silicon 0.01-0.2 oxygen 0.0001-0.002 nitrogen 0.0001-0.002 nickel rest

(description of the patent of the Russian Federation for the invention No. 2365656, IPC C22C 19/05, published on 08.27.2009).

, удельный вес сплава равен 8,84 г/см³.The alloy is designed for casting working and nozzle blades of gas turbine engines and installations with directional columnar and single crystal structures. The alloy has a fairly high level of heat resistance

, the specific gravity of the alloy is 8.84 g / cm ³ .

However, the cost of its charge is very high, which seriously reduces the volume of practical application of this alloy.

Known casting heat-resistant alloy based on Nickel for casting vanes with a single crystal structure, having the following average composition, wt.%:

chromium 6.0 cobalt 10.0 molybdenum 0.6 tantalum 9.0 tungsten 9.0 aluminum 5.7 titanium 0.8 hafnium 0.2 nickel rest

(Jacqueline W. Wach, Ken Harri “New Single Crystal Heat Resistant Alloys CMSX-7 and CMSX-8”, Cannon-Muskegon, “Superalloys 2012”, TMS-2012, pp 179-188, edited by Eric S. Hyron and others .).

. Удельный вес сплава составляет 8,8 г/см³.The alloy does not contain rhenium, but the level of its heat resistance is not high enough -

. The specific gravity of the alloy is 8.8 g / cm ³ .

The closest analogue, taken as a prototype, is a casting heat-resistant alloy based on Nickel, having the following chemical composition, wt.%:

chromium 5.0-8.0 cobalt 9.0-12.0 tungsten 14.0-16.0 aluminum 4.0-6.0 tantalum 6.0-10.0 carbon 0.002-0.1 yttrium 0.001-0.1 lanthanum 0.001-0.1 cerium 0.001-0.1 silicon 0.01-0.3 magnesium 0.01-0.15 manganese 0.01-0.3 nickel rest

(description of the patent of the Russian Federation for the invention No. 2439185, IPC C22C 19/05, publ. 10.01.2012).

. Однако он отличается и весьма большим удельным весом (γ=9,03 г/см³), что также затрудняет его практическое использование.The alloy is designed for casting working and nozzle blades of gas turbine engines and installations with directional columnar and single crystal structures. The alloy has the highest level of heat resistance among all known rhenium-free analogues.

. However, it differs in a very large specific gravity (γ = 9.03 g / cm ³ ), which also complicates its practical use.

.The objective of the invention is to reduce the specific gravity of heat-resistant nickel alloy to a level of (8.84-8.87) g / cm ³ while maintaining high heat resistance corresponding to the widely used alloy ZhS 32 VI

.

The technical result of the invention is to reduce the specific gravity of the alloy while maintaining a high level of heat resistance.

The technical result is achieved by the fact that the casting heat-resistant alloy based on nickel containing chromium, cobalt, tungsten, aluminum, tantalum, carbon, yttrium, lanthanum, cerium, silicon, manganese, in contrast to the known, additionally contains molybdenum, hafnium, boron and scandium in the following ratio of components, wt.%:

chromium 4.0-9.0 cobalt 9.0-14.0 tungsten 7.0-10.0 molybdenum 1.0-5.0 aluminum 4.0-6.0 tantalum 6.0-10.0 hafnium 0.1-1.0 carbon 0.002-0.1 yttrium 0.001-0.1 lanthanum 0.001-0.1 cerium 0.001-0.1 silicon 0.01-0.2 manganese 0.01-0.3 boron 0.005-0.03 scandium 0.0002-0.01 nickel  rest

In the claimed alloy, the content of heavy tungsten is reduced from (14.0-16.0) wt.% To (7.0-10.0) wt.%. Tungsten is one of the elements that have a significant positive effect on the high temperature strength properties of nickel alloys. Therefore, a decrease in its concentration in the alloy was compensated to a certain extent by the introduction of molybdenum in its amount in the amount of (1.0-4.0) wt.%, Which also positively affects the heat resistance, but its specific gravity is ≈1.9 times less. than tungsten.

For the same purpose, hafnium was simultaneously introduced into the alloy composition, which also effectively increases heat resistance, improves (γ-γ ') structure and at the same time its specific gravity is ≈ 1.4 times lower than the specific gravity of tungsten.

In addition, in order to improve the formation of more dispersed precipitates of particles of the strengthening γ-phase of improvement (γ-γ ') hardening in the alloy by improving the state of the interphase boundaries by additional doping with boron and scandium.

The introduction of boron forms borides, which are located at the defective sites of the crystal lattices, thereby limiting their growth, and improving creep resistance.

At the same time, scandium has an accumulative effect on heat resistance and refines the metal, binding sulfur, phosphorus and other harmful impurities to refractory fine particles, which become additional alloy strengthening compounds.

The increase in chromium and cobalt allows you to increase the resistance to the growth of fatigue cracks, increase heat resistance and corrosion resistance, as well as additionally strengthen the solid solution.

An example implementation.

To test the alloy, three experimental alloy compositions were smelted, the content of the components of which are given in table 1.

The alloy was smelted in a VIP-0-10 Leibold Herece vacuum induction furnace with a power of 50 kW and in a vacuum of 10-3 torr.

The obtained billet batch was remelted in order to realize a single-crystal structure using a 450 kW kW VIL unit and a crucible capacity of 10 kg in a vacuum of ~ 10-3 torr using seeds of a given orientation. Smelted samples after etching were subjected to control in order to reject single crystals from spurious grains, as well as to x-ray control in order to determine the crystalline orientation. Samples with crystal deviations from the longitudinal axis of not more than ± 6 ° were transferred to mechanical characteristics tests.

The test results of the mechanical characteristics of the known alloy ZhS32VI and the proposed alloy and their specific gravity are shown in table 2.

As can be seen from the table, the proposed alloy in terms of strength at 20 ° C corresponds to the production alloy ZhS32VI (Encyclopedia "Mechanical Engineering", section II, volume II-3. M .: Mechanical Engineering, 2001, p. 545) and is somewhat inferior in this indicator prototype. However, the new alloy exceeds ZhS32VI (about 17%) and the prototype (about 9%) in terms of yield strength. The ductile characteristics of the proposed alloy are slightly lower, however, they are quite sufficient to ensure reliable operation of the structures and correspond to the prototype.

In terms of long-term strength and specific gravity, the proposed alloy corresponds to the production material ZhS32VI. At the same time, the cost of the charge of the proposed alloy is 7.5 million rubles / t, while the price of the charge of the alloy ZhS32VI, which has the same level of performance, is 17.8 million rubles / t, that is, 2.4 times.

Despite the fact that the proposed alloy is inferior to the prototype in terms of long-term strength, it has a lower specific gravity, due to which turbine blades made from it have a lower mass and experience lower loads due to centrifugal forces. The proposed alloy has an optimal structure: dispersed cubic precipitates of the γ'-phase with a size of (0.35-0.45) microns, a small amount of eutectic phase, characterized by the absence of embrittle TPU phases and α phases based on tungsten, molybdenum, rhenium and chromium. Its structural stability (determined by the temperatures of the onset T _{Нрγ '} and the complete Т _{pr of the} γ'-phase dissolution) is somewhat better than that of the ZhS32VI alloy. Comparative thermodynamic parameters of the proposed alloy and alloy ZhS32VI are shown in table 3.

The invention provides a high level of heat resistance of the alloy while significantly reducing the cost of its charge materials and scarcity due to the absence of extremely expensive and severely deficient rhenium in its composition.

Claims (2)

Nickel-based foundry heat-resistant alloy containing chromium, cobalt, tungsten, aluminum, tantalum, carbon, yttrium, lanthanum, cerium, silicon and manganese, characterized in that it additionally contains molybdenum, hafnium, boron and scandium in the following ratio of components, wt .%: chromium  4.0-9.0 cobalt  9.0-14.0 tungsten  7.0-10.0 molybdenum  1.0-5.0 aluminum  4.0-6.0 tantalum  6.0-10.0 hafnium  0.1-1.0 carbon  0.002-0.1 yttrium  0.001-0.1 lanthanum  0.001-0.1 cerium  0.001-0.1 silicon  0.01-0.2 manganese  0.01-0.3 boron  0.005-0.03 scandium  0.0002-0.01 nickel rest