RU2256715C1 - Nickel-base heat-resistant alloy and article made of thereof - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to preparing nickel-base heat-resistant casting alloys. Invention proposes nickel-base casting heat-resistant alloy and article made of thereof. Alloy comprising chrome, cobalt, tungsten, molybdenum, titanium, niobium, aluminum, boron, yttrium and carbon comprises additionally tantalum, silicon and calcium in the following ratio of components, wt.-%: chrome, 5.0-9.0; cobalt, 5.0-10.0; tungsten, 8.0-12.0; molybdenum, 0.5-2.5; titanium, 1.0-3.0; niobium, 1.0-1.8; aluminum, 4.5-6.0; boron, 0.001-0.002; yttrium, 0.005-0.05; carbon, 0.05-0.25; tantalum, 0.25-1.5; silicon, 0.01-0.1; calcium, 0.001-0.01, and nickel, the balance. Alloy provides enhancing resistance against arising burning cracks in casting turbine vanes with unidirectional grains structure in combination with level of heat resistance and thermal stability. Invention can be used for making gas-turbine engines and equipment unit members being turbine vanes with monocrystalline and directed structure mainly working at high temperature by method of directed crystallization.

EFFECT: improved and enhanced properties and quality of alloy.

3 cl, 3 tbl, 1 ex

Description

The invention relates to the field of metallurgy and can be used to obtain by the method of directional crystallization of parts of high-temperature units of gas turbine engines and installations, mainly turbine blades with single-crystal and directional structures.

Nickel-based casting heat-resistant alloys containing tungsten, chromium, molybdenum, hafnium, niobium, cobalt, and aluminum, such as MAR-M247, ZhS26, ZhS26U, which have a high level of long-term strength and are used in aircraft gas turbine engines, are widely known in metallurgy (Patent US No. 3748192, RF patent No. 722330, RF patent No. 1412342).

However, MAR-M247 and ZhS26U alloys have not proved to be sufficiently effective when used in modern directional crystallization technology, namely in casting technology using a liquid metal cooler, which provides a sharp increase in the strength properties of the material due to an increase in the crystallization gradient. So, the ZhS26U and MAR-M247 alloys turned out to be low-tech, prone to hot cracking, and the ZhS26 alloy, although it had high heat resistance and manufacturability, was characterized by low heat resistance due to the hardener vanadium included in its composition. These drawbacks limit the use of alloys in new generation gas turbine engines.

The closest in chemical composition and purpose to the proposed invention is a heat-resistant foundry nickel alloy ZhS26U having a chemical composition in the following ratio of components, wt.%:

Alloy - the prototype is used to produce castings of blades with a unidirectional structure. However, this alloy is characterized by extremely low manufacturability in high-gradient casting using mold cooling in a melt of low-melting metal (aluminum, tin). This is due to the presence of hafnium in the alloy, which forms a series of low-melting eutectics of the type Ni ₃ Hf or Ni ₅ Hf along the grain boundaries. Due to the occurrence of thermal stresses within the effective range of crystallization along the grain boundaries, where the non-crystallized eutectic phases accumulate, so-called hot cracks arise, which are a defect in all cases that make the blade unusable.

The technical task of the invention is the development of a heat-resistant cast nickel alloy and products made of it, which are highly adaptable to high-gradient directional crystallization, in particular, high resistance to the occurrence of hot cracks when casting turbine blades with a unidirectional grain structure in combination with a high level of heat resistance and heat resistance.

To achieve this goal, a heat-resistant nickel-based alloy is proposed, containing chromium, cobalt, tungsten, molybdenum, aluminum, titanium, niobium, boron, yttrium, carbon, characterized in that it additionally contains tantalum, silicon, calcium in the following ratio of components, wt. %:

а значит и повышает прочностные характеристики материала. Наличие в сплаве тантала помимо повышения длительной прочности повышает технологичность, так как уменьшает вероятность возникновения полос струйчатой ликвации (цепочки равноосных зерен, являющихся дефектом структуры лопатки). Добавление кальция в количестве 0.001-0.01 мас.% снижает содержание в сплаве кислорода, который резко отрицательно влияет на технологические свойства сплава при монокристаллическом литье. Для удаления оставшихся в сплаве дисперсных включений вводят кремний (0,01-0,1 мас.%), который превращается в оксид, соединяясь с кислородом. Оксид кремния, соединяясь с оксидом кальция, образует легкоплавкое соединение, которое в процессе плавки уходит в футеровку тигля.Removing hafnium from the composition of the alloy dramatically increases the resistance of the casting to cracking during casting. Introduced into the alloy tantalum (up to 1.5 wt.%) Intensifies the secondary

and therefore increases the strength characteristics of the material. The presence of tantalum in the alloy, in addition to increasing long-term strength, increases manufacturability, as it reduces the likelihood of streak segregation (chains of equiaxed grains that are a defect in the structure of the blade). The addition of calcium in an amount of 0.001-0.01 wt.% Reduces the oxygen content in the alloy, which sharply negatively affects the technological properties of the alloy during single crystal casting. To remove the dispersed inclusions remaining in the alloy, silicon (0.01-0.1 wt.%) Is introduced, which is converted into oxide, combining with oxygen. Silicon oxide, combining with calcium oxide, forms a low-melting compound, which in the process of melting goes into the lining of the crucible.

Products obtained from the proposed alloy have high technological properties, heat resistance and heat resistance.

An example implementation.

In laboratory conditions, the proposed alloys were cast, the compositions of which are presented in table 1, where compositions 1, 2, 3 are the proposed alloys; and composition 4 is an alloy prototype.

Tables 2 and 3 present the test results for heat resistance, heat resistance and crack resistance of the proposed alloy (compounds 1, 2, 3) in comparison with the prototype alloy (composition 4).

The experiments were carried out on industrial installations of directional crystallization UVNK-8P (liquid metal crystallizer - aluminum). Control fill was carried out on special test blocks. The blocks are made of ceramic based on electrocorundum with a binder - hydrolyzed solution of ethyl silicate-40. The casting was carried out by a prototype alloy containing up to 0.3 wt.% Hafnium, and alloys having a composition within the scope of the invention.

To test the tendency to crack formation, a special technique was proposed, which included pouring a special casting block and analysis of the macrostructure of the obtained castings. In the proposed block of 9 cylindrical billets arranged in three rows, two or three cylindrical billets in each row were connected by plates 1-1.5 mm thick. During the process of high-gradient directional crystallization, grain boundaries appeared on these plates (metal sprouted from different cylindrical billets). In the event of a crack along the grain boundary, it was believed that the alloy has insufficient crack resistance. Otherwise, crack resistance was satisfactory.

As can be seen from tables 2 and 3, the proposed alloy has a high level of heat resistance and heat resistance at the level of the known alloy, in terms of crack resistance, the proposed alloy is an order of magnitude higher than the prototype alloy.

Thus, the proposed alloy has the manufacturability necessary to obtain castings under conditions of high gradient crystallization, and reduces the rejects of working blades of gas turbine engines and plants by hot cracks by an order of magnitude, which will increase the resource and reliability of gas turbine engine products made of the proposed alloy.

Table 1.
The chemical composition of the alloys. Alloying elements The content of alloying elements (wt.%) Suggested Alloys Prototype Alloy * 1 2 3 Chromium 9.0 5,0 7.0 5.3 Cobalt 7.5 10.0 5,0 10.7 Tungsten 8.0 10.0 12.0 12.0 Molybdenum 2,5 0.5 1,5 1.05 Titanium 1,0 2.0 3.0 1.8 Niobium 1.8 1,0 1.4 1.3 Aluminum 5.2 6.0 4,5 7.5 Boron 0.001 0.01 0.02 0.17 Yttrium 0.05 0.005 0,025 0.01 Carbon 0.05 0.15 0.25 0.1 Hafnium - - - 0.3 Tantalum 0.8 1,5 0.25 - Silicon 0.05 0.01 0.01 - Calcium 0.001 0.005 0.01 - Cerium - - - 0,03 Lanthanum - - - 0,025 Praseodymium - - - 0.012 Neodymium - - - 0.09 Nickel rest

table 2
Tendency to crack resistance during directional crystallization of a casting in a high-gradient UVK-8P furnace. Alloy number The length of a hot crack, mm Crack count 1 0.2-0.3 1-2 2 0 0 3 0 0 Prototype alloy up to 25 8

Table 3
Alloy Properties Alloy The durability of the samples when tested for long-term strength mode, hour Prywes samples 1100 ° C-100 h, g / m ² The weight gain of the samples 1000 ° C-225 hours, g / m ² T = 975 ° C
σ = 270 MPa T = 1100 ° C
σ = 120 MPa 1 75 86 16 thirteen 2 80 90 14 10 3 76 85 14 eleven 4 78 88 fifteen eleven where, σ = 270 MPa and σ = 120 MPa - mechanical stress when tested for long-term strength at specified temperatures

Claims (2)

1. Heat-resistant casting alloy based on nickel, containing chromium, cobalt, tungsten, molybdenum, titanium, niobium, aluminum, boron, yttrium and carbon, characterized in that it additionally contains tantalum, silicon and calcium in the following ratio of components, wt.% : Chrome 5.0-9.0 Cobalt 5.0-10.0 Tungsten 8.0-12.0 Molybdenum 0.5-2.5 Titanium 1.0-3.0 Niobium 1.0-1.8 Aluminum 4.5-6.0 Boron 0.001-0.02 Yttrium 0.005-0.05 Carbon 0.05-0.25 Tantalum 0.25-1.5 Silicon 0.01-0.1 Calcium 0.001-0.01 Nickel Else 2. A product from a heat-resistant casting alloy based on nickel, characterized in that it is made of an alloy according to claim 1.