RU2655484C1 - HEAT-RESISTANT Ni-BASED ALLOY AND PRODUCT MADE OF IT - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, in particular to corrosion and heat resistant Ni-based alloys, and can be used for production of parts of gas turbine engines and units, long-term operating in corrosive environments at temperatures up to 700 °C. Heat-resistant cast Ni-based contains, wt%: carbon up to 0.08, chromium 16–20; aluminium 0.5–2.0; titanium 0.5–2.0; molybdenum 2.0–3.5; iron 8.0–11.0; niobium 4.0–6.0; boron up to 0.02; tungsten 0.5–2.5; cobalt 8.8–10.2; zirconium up to 0.08; lanthanum up to 0.20; barium up to 0.03; rhenium up to 0.02; hafnium up to 0.10; nickel – the rest being.

EFFECT: long-term strength, corrosion resistance, structural stability, service life of an alloy at a temperature of 650 °C increase.

2 cl, 2 tbl, 5 ex

Description

The invention relates to metallurgy, and in particular to corrosion-resistant heat-resistant nickel-based alloys intended for the manufacture of parts for gas turbine engines and plants operating for a long time in aggressive environments at temperatures up to 700 ° C.

Known heat resistant nickel alloy of the following chemical composition, mass. %:

chromium 15-23 molybdenum 2-4 niobium or tantalum 4-8 aluminum no more than 0.2 titanium no more than 0.2 carbon no more than 0.10 silicon no more than 0.50 boron 0.005-0.015 iron up to 30.0 manganese up to 1.0 nickel or cobalt 45-60

(US 3,046,108 A, 7/24/1962).

The alloy has low values of long-term strength at temperatures in the range of 600-650 ° C, as well as reduced corrosion resistance.

Known heat resistant nickel alloy of the following chemical composition, mass. %:

carbon 0.005-0.03 chromium 14-18

iron 15-45

aluminum 0.5-2.0 nitrogen 0.005-0.05 titanium 0.5-2.0 niobium 1,5-5,0 nickel rest

(US 8043068 B2, 10/25/2011).

The alloy has reduced structural stability: during operation, irreversible changes occur in its structure and undesirable topologically close-packed (TPU) phases (σ, δ, etc.) are formed, which embrittle the metal and thereby reduce mechanical properties.

Known alloy based on Nickel of the following chemical composition, mass. %:

chromium 17-21 carbon 0.01-0.05 manganese max 0.35 silicon max 0.35 phosphorus 0.004-0.020 sulfur max 0,0025 molybdenum 2.5-3.1 niobium 5.2-5.8 titanium 0.5-1.0 aluminum 1.2-1.7 cobalt 8-10 tungsten 0.8-1.4 boron 0.003-0.008 copper max 0.3 iron 8-10 nickel rest

(US 8551266 B2, 10/08/2013).

The alloy has reduced characteristics of long-term and short-term strength at a temperature of 650 ° C, and is also prone to the formation of TPU phases (σ, δ, etc.) during operation.

The closest analogue is a nickel-based alloy, designed to obtain various parts of a gas turbine engine, such as disks, blades, shafts, casing, and containing, mass. %:

carbon no more than 0.10 chromium 12-20 molybdenum up to 4 tungsten until 6 cobalt 5-12 iron until 14 niobium 4-8 aluminum 0.6-2.6 titanium 0.4-1.4 phosphorus 0.003-0.03 boron 0.003-0.015 nickel rest

and the total content of molybdenum and tungsten is 2-8 mass. %, the total content of aluminum and titanium is 2-6 at. %, the ratio of the amount of aluminum to titanium (in at.%) is 1.5, the ratio of the total content of aluminum and titanium (in at.%) to the content of niobium (in at.%) is 0.8-1, 3 (US 6730264 B2, 04/04/2004).

This alloy has low values of long-term strength, corrosion resistance and a limited service life in the engine due to the formation of a σ-phase in the structure during operation.

The technical task of the invention is the development of a heat-resistant alloy based on Nickel with improved performance.

The technical result of the invention is to increase long-term strength, corrosion resistance, structural stability, increase the life of the alloy at a temperature of 650 ° C.

To achieve a technical result, a heat-resistant nickel-based casting alloy is proposed, containing carbon, chromium, aluminum, titanium, molybdenum, iron, niobium, boron, tungsten, cobalt, as well as zirconium, lanthanum, barium, rhenium and hafnium, with the following ratio of components, mass %:

carbon up to 0.08 chromium 16-20 aluminum 0.5-2.0 titanium 0.5-2.0 molybdenum 2.0-3.5 iron 8.0-11.0 niobium 4.0-6.0 boron up to 0.02 tungsten 0.5-2.5 cobalt 8.8-10.2 zirconium up to 0.08 lanthanum up to 0.20 barium up to 0.03 rhenium up to 0.02 hafnium up to 0.10 nickel rest

Also proposed is a product made of this alloy.

Compared with the prototype alloy, the proposed alloy contains small strictly regulated amounts of zirconium, lanthanum, barium, rhenium and hafnium.

It was found that the additional introduction of lanthanum and barium into the alloy made it possible to reduce the rate of high-temperature sulfide-oxide and chloride corrosion by creating a protective barrier layer on the metal surface based on thermodynamically highly stable compounds with lanthanum and barium, which weakens the diffusion fluxes of sulfur and oxygen ions, and also reduces the microporosity of the oxide film.

The introduction of zirconium together with hafnium provides stabilization of the structural components of the alloy, in particular carbides, helps to strengthen grain boundaries by suppressing the formation of low-melting compounds, thereby increasing the life of the engine and eliminating the formation of embrittlement phases during the production process.

The introduction of rhenium allows you to further strengthen the γ-solid solution of the alloy and thereby increase the heat-resistant properties.

In addition to the positive effect of lanthanum on the corrosion properties of the alloy, it was also found that, upon its introduction, finely dispersed nanosized particles of the γ 'phase are formed in the structure, which are released in the γ-solid solution between the larger particles of the γ' phase, block and delay the dislocation movement in the process creep of metal at elevated temperature and voltage, thereby providing increased heat resistance.

Examples of implementation.

In the VIAM2002 vacuum induction furnace, five melts of the proposed alloy and one melting of the alloy taken as a prototype were smelted. The weight of each heat was 10 kg. All melts were melted in the UPPF-U vacuum melting and casting unit and cast into ceramic blocks with blanks for samples with equiaxial structure.

After the heat treatment, samples for testing the long-term strength at high temperatures, as well as samples for testing for sulfide-oxide and chloride corrosion, were made from billets.

The compositions of the alloy samples are shown in table 1.

Long-term strength tests were carried out at a temperature of 650 ° C and a voltage of 650 MPa. Two samples were tested from each heat. The test results are shown in table 2.

Corrosion tests were carried out in a cyclic mode. One test cycle included:

- applying to the hot surface of the salt crust samples an aqueous solution of a mixture of salts of 75% Na ₂ SO ₄ + 25% NaCl (for sulfide-oxide corrosion) or a 3.5% aqueous solution of NaCl (for chloride corrosion);

- exposure of samples at T = 650 ° C for 1 hour in a heating furnace;

- air cooling.

The total test duration is 30 cycles.

The corrosion resistance of the samples was evaluated by the specific change (decrease) in the mass by weighing the samples every 5 cycles.

For each type of corrosion test, 6 samples were made. The average test results for 6 samples for long-term strength and corrosion are shown in table 2.

The results show that the time before the destruction of the proposed alloy during tests for long-term strength at a temperature of 650 ° C significantly exceeds the durability of the prototype alloy, i.e. the service life of the proposed alloy in comparison with the alloy prototype can be increased.

The proposed alloy has a higher corrosion resistance at a temperature of 650 ° C in a sulfide-oxide and chloride environment than the prototype alloy: the specific change (decrease) in the mass of samples in both environments of the proposed alloy is significantly less.

A metallographic analysis of the structure of the destroyed samples after testing for long-term strength at a temperature of 650 ° C did not reveal the formation of embrittlement TPU phases (σ, μ, etc.), which confirms the phase and structural stability of the proposed alloy.

Thus, the proposed alloy significantly exceeds the well-known alloy in terms of durability and corrosion resistance, which will increase the service life and reliability of products of gas turbine engines and installations that operate for a long time in aggressive environments at elevated temperatures and voltages.

* elements are present in the alloy, but in a smaller amount, is there really a limit to the sensitivity of the method for determining the concentration of components (less than 0.00005 wt.%)

Claims (3)

1. A heat-resistant casting alloy based on nickel, containing carbon, chromium, aluminum, titanium, molybdenum, iron, niobium, boron, tungsten and cobalt, characterized in that it additionally contains zirconium, lanthanum, barium, rhenium and hafnium, in the following ratio components, wt. %: carbon   up to 0.08 chromium   16-20 aluminum   0.5-2.0 titanium   0.5-2.0 molybdenum   2.0-3.5 iron   8.0-11.0 niobium   4.0-6.0 boron   up to 0.02 tungsten   0.5-2.5 cobalt   8.8-10.2 zirconium   up to 0.08 lanthanum   up to 0.20 barium   up to 0.03 rhenium   up to 0.02 hafnium   up to 0.10 nickel   rest. 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.