RU2808314C2 - Method for producing nickel alloy powder with good corrosion resistance and high tensile strength and its application (options) - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates namely to a method for producing powder from a nickel alloy with high resistance to hydrogen embrittlement and high mechanical properties, as well as to its applications. Method for producing powder from a nickel alloy containing, in wt.%: Ni 50 – 55, Cr 17 – 21, Mo > 0 – 9, W 0 – < 9, Nb 1 – < 5.7, Ta > 0 – 4.7, Ti 0.1 – 3.0, Al 0, 4 – 4.0, Co no more than 3.0, Mn no more than 0.35, Si no more than 0.35, Cu no more than 0.23, C 0.001 – 0.045, S no more than 0.01, P 0.001 – 0.02, B 0.001 – 0.01, the rest is Fe and the usual production-related impurities, when the following ratios are met: Nb + Ta: > 1 – 5.7, Al + Ti: > 1.2 – 5, Mo + W: 3 – 9, includes smelting the alloy in a vacuum induction furnace, holding the melt for 5 minutes to 2 hours for homogenization, installation in a closed spray unit with gas supply, dew point from -10 to 120°C, injection of the melt through a nozzle into a gas flow at a gas flow rate from 2 m³/min to 150 m³/min, collecting cured powder particles in a hermetically sealed container and hermetically sealed packaging of the powder in a protective gas atmosphere containing argon. In this case, the particle size ranges from 5 to 250 microns, the powder particles are spherical, the powder contains gas inclusions with a pore area of more than 0.0 to 4% (pores > 1 micron) of the total surface of the objects being evaluated, the apparent density of the powder ranges from 2 to alloy density of 8 g/cm³.

EFFECT: resulting powder has high mechanical properties, as well as high resistance to hydrogen embrittlement.

10 cl, 37 dwg, 8 tbl

Description

The invention relates to a method for producing nickel alloy powder with high resistance to hydrogen embrittlement and very good mechanical properties, as well as to its applications.

Age-hardening nickel alloys have long been used in the oil and gas industry in applications where increased strength is required. In this application, good corrosion resistance is required, in particular in atmospheres containing H ₂ S and Cl, in combination with good mechanical properties. Yield strength, notched toughness, and strength are additional important criteria for material selection. Examples from the prior art are given in Table 1.

Suitable materials for this application include Alloy 718, which has the following chemical composition (wt.%): 18.5% chromium, <0.1% carbon, 18% iron, 0.9% titanium, 0.6% aluminum, 3% molybdenum, 5% niobium + tantalum, the rest is nickel and fusible impurities. Increasing demands on this material make it necessary to develop a new nickel alloy with improved properties.

Alloy 718 is the material of choice for applications that require the highest levels of mechanical strength. In this case, the temperature during use does not exceed about 200°C. The material has good anti-corrosion properties against hydrogen embrittlement and corrosion cracking, as well as high mechanical strength. Due to the representative use of Alloy 718, this alloy is considered the basis for improvement or new development.

Table 1. Examples from the prior art No. Universal Designation System for Metals and Alloys (UNS) NO7718 NO6625 NO7716 NO9925 NO5500 NO7725 Name of material Alloy 718 Alloy 625* Alloy 625 plus Alloy 925 Alloy
K-500* Alloy 725 Chemical composition WITH Max. 0.045 Max. 0.10 Max. 0.030 Max. 0.025 Max. 0.25 Max. 0.030 Mn Max. 0.35 Max. 0.50 Max. 0.20 Max. 1.00 Max. 1.5 Max. 0.35 Cr 17.0 - 21.0 20.0 - 23.0 19.0 - 22.0 19.5 - 23.5 19.0 - 22.5 Ni 50.0 - 55.0 rest 59.0 - 63.0 42.0 - 46.0 63.0 - 70.0 55.0 - 59.0 Mo 2.80 - 3.30 8.0 - 10.0 7.0 - 9.5 2.50 - 3.50 7.00 - 9.50 P Max. 0.010 Max. 0.015 Max. 0.015 Max. 0.020 Max. 0.02 Max. 0.015 Cu Max. 0.23 1.50 - 3.00 rest Al 0.40 - 0.60 Max. 0.40 Max. 0.35 0.10 - 0.50 2.30 - 3.15 Max. 0.35 Ti 0.80 - 1.15 Max. 0.40 1.0 - 1.6 1.90 - 2.40 0.35 - 0.85 1.00 - 1.70 Nb 4.75 - 5.50 3.15 - 4.15 2.75 - 4.00 0.08 - 0.50 2.75 - 4.00 B Max. 0.0060 Max. 0.006 Fe rest Max. 5.0 5 min. 22 Max. 2.0 rest

(API Standard 6ACRA *NACE MR 0175).

Alloy 718 is a wrought and age-hardening nickel-chromium alloy developed by H. Eiselstein and patented in 1962, Patent No. US 3,046,108. Alloy 718 has a good combination of high strength properties with good ductility over a wide temperature range. The material was developed for the aircraft industry, and a few years later was introduced into the oil and gas industry due to its combination of good corrosion resistance and good mechanical properties.

US 3,160,500 disclosed a matrix-strengthened nickel-chromium alloy, which subsequently led to the creation of Alloy 625, which has a combination of good mechanical properties over a wide temperature range and high resistance to fracture and stress at elevated temperatures. Due to its attractive combination of strength and corrosion resistance, this material has found wide application. High levels of chromium and molybdenum provide good corrosion resistance and strength, while iron and niobium provide additional strength. Additives of aluminum and titanium serve primarily metallurgical purposes and are kept at low levels to improve weldability. The alloy has the following composition: 21.44 - 21.68% Cr, 0.02 - 0.03% C, 0.11 - 0.12% Mn, 0.04 - 0.11% Si, 8.83 - 9 .1% Mo, up to 5.32% W, 4.19 - 4.35% Nb, 0.16 - 0.23% Al, 0.13 - 0.20% Ti, 1.92 - 6.89% Fe, up to 0.02% Mg, the rest is Ni.

DE 10 2015 016 729 A1 describes a method for producing a nickel-based alloy, wherein

- the electrode is made in a vacuum induction furnace,

- to reduce stress and overaging, the electrode is subjected to heat treatment in an oven in the temperature range from 400 to 1250°C for 10-336 hours,

- in air or in an oven, depending on the dimensions, in particular the diameter, the electrode is cooled to a temperature ranging from room temperature to less than 1250°C, in particular to less than 900°C,

- then the cooled electrode is remelted using vacuum-arc remelting at a remelting speed from 3.0 to 10.0 kg/min to obtain a vacuum-arc remelting ingot,

- the resulting vacuum-arc remelting ingot is subjected to heat treatment in a furnace in a temperature range from 400 to 1250°C for 10-336 hours,

- depending on the size, in particular the diameter, the resulting vacuum-arc remelting ingot is cooled in air or in a furnace to a temperature ranging from room temperature to less than 1250°C, in particular to less than 900°C,

- this vacuum-arc remelting ingot is remelted again at a remelting speed of 3.0 to 10 kg/min,

- the remelted vacuum-arc remelting ingot is subjected to heat treatment at a temperature range from 400 to 1250°C for 10-336 hours,

- then the vacuum-arc remelting ingot is brought to the desired size and shape of the product by means of hot and/or cold deformation.

The nickel-based alloy may have the following composition:

no more than 0.25% C, no more than 0.15% S, 17-32% Cr, 45-72% Ni, no more than 1% Mn, no more than 1% Si, no more than 3.25% Ti, no more 5.5% Nb, no more than 5% Cu, no more than 25% Fe, no more than 0.03% P, no more than 3.15% Al, no more than 0.6% V, no more than 0.12% Zr, no more than 28% Co, no more than 0.02% B, and production-related impurities.

Based on Alloy 625 and Alloy 718, Alloy 625 plus was developed. Alloy 625 plus is a high strength alloy as an alternative to Alloy 625, with similar corrosion resistance due to its higher titanium content.

The purpose of the age-hardening alloy, called Alloy 925, is very similar to the purpose of Alloy 718. They are used to make rods and pipes for oil sources, structural parts for gas sources, valves, drill collars, connecting components and packers. Alloy 925 is used when the strength requirements are slightly lower than for Alloy 718.

Niccoros Alloy K-500 (NO5500) is a nickel-copper alloy that can be age-hardened through the formation of a gamma phase. It is used in the offshore industry, which is not heavily burdened by hydrogen sulfide. Corrosion resistance in acid gas environments and mechanical strength are lower compared to Alloy 718 and Alloy 925.

Alloy 725 has high mechanical strength similar to Alloy 718 and corrosion resistance similar to Alloy 625.

The content and presence of age-hardening phases have a noticeable and direct effect on the resistance to hydrogen embrittlement. According to the literature, materials that do not contain precipitate phases and, therefore, are not age-hardening, have noticeably better resistance to hydrogen embrittlement compared to age-hardening materials containing precipitate phases.

The basis of the invention is to provide an alloy based on Alloy 718, which, in addition to improved resistance to acid gas and hydrogen embrittlement, would also have a higher yield strength and higher strength, preferably a lower proportion of delta and gamma phases and a higher gamma phase fraction'.

It is also an object of the invention to provide a process for producing an Alloy 718-based alloy by which higher yield strength and higher strength can be achieved while providing a low proportion of delta and gamma phases and a higher proportion of gamma phase.

This problem is solved by a method for producing powder from a nickel-based alloy containing, wt.%:

Ni: 50 - 55

Cr: 17 - 21

Mo: > 0 - 9

W: 0 - < 9

Nb: 1 - < 5.7

Ta: > 0 - 4.7

Ti: 0.1 - 3.0

Al: 0.4 - 4.0

Co: no more than 3.0

Mn: no more than 0.35

Si: no more than 0.35

Cu: no more than 0.23

C: 0.001 - 0.045

S: no more than 0.01

R: 0.001 - 0.02

B: 0.001 - 0.01

the rest is Fe and the usual production-related impurities,

when the following relations are met:

Nb + Ta: > 1 - 5.7 … (1)

Al + Ti: > 1.2 - 5 … (2)

Mo + W: 3 - 9 … (3),

where Nb, Ta, Al, Ti, Mo and W are the content of the corresponding elements in wt.%,

including:

- smelting the alloy in a vacuum induction (VIM) furnace,

- holding the melt for 5 minutes to 2 hours for homogenization,

- installation in a closed spray unit with gas supply, dew point from -10 to 120°C,

- injection of the melt through a nozzle into the gas flow at a gas flow rate from 2 m ³ /min to 150 m ³ /min,

- collecting hardened powder particles in a hermetically sealed container, while

particle size ranges from 5 to 250 microns,

the powder particles are spherical,

the powder contains gas inclusions with a pore area of more than 0.0 to 4% (pores > 1 μm) of the total surface of the objects being assessed,

the apparent density of the powder ranges from 2 to the density of the alloy, which is 8 g/cm ³ ,

- sealed packaging of the powder in a protective gas atmosphere containing argon.

Preferred options for the development of this method according to the invention are given in the corresponding dependent claims of the method.

The following combinations can be achieved through alternative smelting processes:

VIM / (ESR or VAR) / if necessary (ESR or VAR)

EF (electric oven) / (VOD or AOD) / VAR/VAR.

The alloy according to the invention can be used preferably for the following types of products:

- rod,

- wire,

- band,

- leaf,

- longitudinally welded pipe,

- seamless pipe,

- powder.

Semi-finished products/structural parts find their application preferably in the oil and gas and chemical industries.

The presence of any evolution phases was analyzed and studies were carried out to better understand the interaction between the hydrogen atom and the crystal structure when the hydrogen atom occupies different positions in the unit cell. A calculation was made of the preferred sites for hydrogen capture along phase boundaries or in the matrix material, taking into account the enthalpy energy of hydrogen when this site is occupied. Based on these results, multiple tensile tests were carried out to investigate the bonding ratios between metal atoms near the phase boundaries.

According to the present invention, the presence of a hydrogen atom in the most stable position at the gamma/gamma' phase boundary has no effect on the tensile strength compared to a system without the presence of hydrogen atoms (Fig. 1). In contrast, in the case when the hydrogen atom occupies the most stable position at the gamma/gamma phase boundary, significant movement of the atom occurs and the system exhibits lower tensile strength compared to a system without a hydrogen atom (Fig. 2), which indicates that hydrogen embrittlement may occur. The delta phase, which is not present in representative amounts in Alloy 718 for oil and gas applications, does not have a significant effect on the mechanical properties (Fig. 3).

Alloy 718 is available in three different grades to meet different yield strength requirements. The 120K option has a minimum yield strength of 120 thousand pounds per square inch (ksi), achieved by age strengthening at temperatures from 774 to 802°C. Option 140K has a minimum yield strength of 140 ksi, provided by aging hardening at a temperature of 760 - 802°C. 150K is an option produced by two-stage aging hardening at a first temperature of 700 to 750°C and a second temperature from 600 to 659°C, which has a minimum required yield strength of 150 ksi.

Different heat treatment methods are capable of creating different microstructures (Fig. 4), which were examined for comparison with hydrogen embrittlement behavior. The gamma' phase is released in the form of point particles, while the gamma' phase is needle-shaped.

A lower ratio between the mass fractions of the gamma'/gamma'' phases produces the most unfavorable behavior with respect to hydrogen embrittlement, while a higher ratio between the mass fractions of the gamma'/gamma'' phases provides better resistance to hydrogen embrittlement. This information is shown in Table 2.

Resistance to hydrogen embrittlement was tested using gradual loading tests with cathodic polarization in accordance with NACE (National Association of Corrosion Engineers) publication 3948, 2014. Specimens were tested in an inert environment (deionized water, nitrogen purge at 40°C) and in an aggressive environment. environment (0.5 M sulfuric acid solution at 40°C with a current density of 5 mA/cm ² to achieve cathodic polarization) and determined the elongation ratio at break between the aggressive and inert media. The higher elongation at break ratio could explain why the resistance to hydrogen embrittlement was also higher.

The particle size of gamma' and gamma'' precipitates can also affect the mechanical and anti-corrosion properties of nickel alloys.

Typical conditions that cause hydrogen embrittlement to occur are contact of the material with atomic or molecular hydrogen in combination with stress on the material.

The reasons for adding alloying elements to Alloy 718 nickel alloy, which is widely used in the oil and gas industry, are as follows.

Iron is effective in reducing the cost of the metal, but due to the deterioration of the material's properties, it should not be used excessively for alloying.

Chromium is used to increase strength at room temperature while providing overall corrosion resistance. When combined with carbon, chromium forms carbides, which increase strength at high temperatures.

In general, it should be noted that resistance to pitting corrosion in chlorine-containing environments increases with increasing molybdenum content. As the molybdenum content increases, the resistance to stress corrosion at high temperatures also improves. If necessary, molybdenum can be replaced with tungsten.

The austenitic matrix from the gamma phase is strengthened by aging as a result of intermetallic precipitates of the gamma', ordered face-centered cubic phase of Ni ₃ (Al/Ti), and the gamma' - tetragonal phase of Ni ₃ Nb, therefore aluminum, titanium and niobium are used as alloying additives . If necessary, niobium can be replaced with tantalum. Due to the cost of the metal, niobium is preferably used. Increasing the amount of aluminum and titanium should lead to more gamma', and decreasing the amount of niobium limits the formation of gamma'.

The delta phase is the equilibrium phase of the precipitation hardening gamma phase (Ni ₃ Nb) and, according to the applicable specification, can only be present in the microstructure in very small quantities, since it negatively affects the mechanical and anti-corrosion properties. The formation of the delta phase is prevented by solution annealing at a temperature above the solvus temperature of the delta phase.

In reducing atmospheres, hydrogen is able to penetrate the material, which can lead to hydrogen embrittlement. The presence of hydrogen atoms in the crystal structure of the material leads to a weakening of the bonds between atoms. This causes loss of tensile strength and can lead to failure of the material under mechanical loading.

The nickel alloy according to the invention, with sufficiently high contents of titanium, aluminum, molybdenum and niobium and in combination with certain heat treatments, is characterized by excellent resistance to hydrogen embrittlement, and at the same time:

• good strength

• good resistance to corrosion cracking and pitting

• good phase stability

• good processing ability.

The nickel content ranges from 50 to 55%, with the following preferred ranges available:

- 51 - 55%

- 52 - 55%

- 53 - 55%.

Lower nickel contents can be replaced by cobalt, but due to the cost of the metal, nickel is preferably used.

Cobalt is contained in the alloy in an amount of no more than 3%. Preferred contents would be:

- 0.01 - 1%

- 0.01 - no more than 0.8%

- 0.01 - no more than 0.6%

- 0.01 - no more than 0.4%.

The chromium element content range is from 17 to 21%, and the following ranges can preferably be set:

- 17 - 20%

- 17 - 19%

- 18 - 19%.

The molybdenum content ranges from > 0 to 9%, and in this case, depending on the application of the alloy, the preferred molybdenum content can be:

- 0.01 - 8.5%

- 0.1 - 8.0%

- 3 - 8%

- 3 - 7%

- > 3.3 - 9%

- 3.75 - 9%.

If necessary, the element molybdenum can be replaced, at least in part, by tungsten, provided that tungsten is not used as an independent element within the specified limits. Combinations of Mo + W are also possible, but depending on the application. In this case, tungsten can be used at a content of 0 to 9%. Preferably, tungsten can be used in the alloy at contents in the following ranges:

-> 0 - 9%

- 0.001 - 9%

- 0.01 - 9%

- 0.1 - 9%

- 19%

- 18

- 3 - 7%

- 3 - 8%

- > 3.3 - 9%.

The niobium content ranges from 1 to 5.7%, and depending on the scope of application, the preferred content of the element can be set within the following limits:

- 2 - 4.5%

- 2 - 4%

- 2 - 3.5%.

The titanium content ranges from >0 to 3.0%. Preferably, the titanium content of the alloy can be set in the following ranges:

- 0.5 - 3.0%

- 1.0 - 3.0%

- 1.0 - 2.0%

- > 1.15 - 3%

- 1.18 - 3%.

The same is true for the element aluminum, which can be contained in the alloy in quantities from 0.4 to 4.0%. Alternatively, the following ranges are also possible:

- 0.6 - 4.0%

- 0.6 - 1.5%

- 0.8 - 4%

- 0.9 - 4.0%

- 1.0 - 4.0%

- 1.0 - 3.3%

- 1.5 - 3.0%.

The element manganese is present in the alloy in an amount of no more than 0.35%.

The element silicon is present in the alloy in an amount of no more than 0.35%.

Copper is contained in the alloy in an amount of no more than 0.23%.

Carbon is contained in the alloy in an amount of no more than 0.045%. Preferably, the carbon content of the alloy can be set in the following ranges:

- 0.001 - no more than 0.035%

- 0.001 - no more than 0.025%

- 0.001 - no more than 0.015%.

The maximum sulfur content in the alloy is 0.01%.

In addition, the alloy contains phosphorus in an amount from 0.001 to 0.02%. Another preferred content is 0.001 - 0.015%.

Boron content ranges from 0.001 to 0.01%, alternatively the following ranges are also acceptable:

- 0.003 - 0.01%

- 0.005 - 0.01%

The rest is iron and production-related impurities.

The following ratio between niobium and tantalum must be observed in order to ensure a sufficient but limited content of gamma phase precipitates:

Nb + Ta = 1 - 5.7%,

where Nb and Ta express the concentration of the corresponding elements in mass%.

Preferred content ranges can be set:

Nb + Ta = < 4.75%

Nb + Ta = 1 - 4.75%

Nb + Ta = 1 - 5.0%

Nb + Ta = 2 - 4%

Nb + Ta = 2 - 3.5%

Nd + Ta = 1.6 - 4%

Nb + Ta = 1 - 4%.

In addition, the following ratio must be observed in order to ensure sufficient stability of the gamma phase:

Al + Ti = >1.2 - 5%,

where Al and Ti express the concentration of the corresponding elements in mass%.

The following preferred ranges can be set:

Al + Ti = 1.5 - 5%

Al + Ti = 1.8 - 5%

Al + Ti = 1.8 - 3.5%

Al + Ti = >1.95%

Al + Ti = >1.95 - 5%.

A ratio of Mo + W = 3 - 9% may occur. If necessary, the following restriction can be applied in this case:

Mo +W = > 3.3%

Mo + W = > 3.3 - 9%.

If the formation of this phase is envisaged, then the following relation must be observed:

Ti/Al > 2 or

Al/Ti > 2,

where Al and Ti express the concentration of the corresponding elements in mass%.

The alloy of the invention is preferably smelted and cast in a vacuum induction furnace (VIM) followed by electroslag remelting (ESR) or vacuum arc remelting (VAR). If necessary, the alloy is re-subjected to electroslag remelting (ESR) or vacuum arc remelting (VAR).

As a possible option, the alloy according to the invention is smelted openly, followed by vacuum-oxygen decarburization (VOD) or argon-oxygen decarburization (AOD), followed by two vacuum arc remelting (VAR) treatments.

The manufactured alloy ingots are subjected to heat treatment, if necessary, at temperatures from 500 to 1250°C for an annealing duration of up to 150 hours, after which they are subjected to hot and/or cold deformation to obtain the desired semi-finished product, such as in the form of billets, rods, wire, sheets , strips and foils, if necessary, with intermediate annealing at temperatures from 800 to 1270 ° C for from 0.05 hours to 100 hours. If necessary, the surface of the material in intervals and/or at the end (including repeatedly) can be abraded chemically and/or mechanically (e.g. roughing, turning, grinding) for cleaning purposes. Then, if necessary, solid solution annealing is carried out in the temperature range from 970 to 1150 ° C for 0.1 h to 60 h, if necessary in an atmosphere of a protective gas, for example, argon or hydrogen, followed by cooling in air, at necessary, in a moving annealing atmosphere, in an inert gas, in water, in a polymer or in oil.

After this, if necessary, annealing for aging hardening is carried out in the temperature range from 600 to 900°C for 0.1 h to 60 hours, if necessary in two stages with additional annealing for aging hardening at 550 - 900°C for from 0.1 hour to 60 hours.

Aging hardening annealing is carried out in the temperature range from 600 to 900°C for 0.1 hour to 60 hours, and the following optimal ranges can be used:

- 600 - 800°C for 0.1 h to 60 h

- 600 - 750°C for 0.1 h to 60 h

- 700 - 900°C for 0.1 h to 60 h

- 750 - 900°C for 0.1 hour to 60 hours.

If necessary, the specified age-hardening annealing is carried out in a two-stage age-hardening, with subsequent age-hardening annealing carried out at 550 - 900 ° C for 0.1 hour - 60 hours, and the following optimal ranges can be set:

- 1st stage of aging hardening in the temperature range from 600 to 800°C for 0.1 hour to 60 hours, 2nd stage of aging hardening in the temperature range from 550 to 750°C for 0.1 hour to 60 h;

- 1st stage of aging hardening in the temperature range from 600 to 800°C for 0.1 hour to 60 hours, 2nd stage of aging hardening in the temperature range from 800 to 900°C for 0.1 hour to 60 h;

- 1st stage of aging hardening in the temperature range from 750 to 900°C for 0.1 hour to 60 hours, 2nd stage of aging hardening in the temperature range from 550 to 750°C for 0.1 hour to 60 h;

- 1st stage of aging hardening in the temperature range from 750 to 900°C for 0.1 to 60 hours, 2nd stage of aging hardening in the temperature range from 750 to 900°C for 0.1 hour to 60 h.

If necessary, in intervals and/or after the last annealing, chemical and/or mechanical cleaning of the material surface (for example, peeling, turning, grinding) can be carried out.

The alloy according to the invention is also well processed and used in the form of rods, wires, strips, sheets, longitudinally welded pipes and seamless pipes.

If necessary, the alloy can be obtained and used in powder form (for example, for additive manufacturing methods). In this case, the powder is produced in a VIGA powder atomizer (Vacuum Induction Gas Atomizer) or through other methods, and is selected or filtered taking into account the desired particle size range of the powder.

Advantageously, the alloy of the invention may be used in applications where hydrogen containing media are present, such as downhole completion tools, packers, drift banks, hangers, valves, thrust brackets, vessels, magnetic logging tool body material (logging while drilling), and etc.

Due to the combination of chemical composition with heat treatment, the alloy according to the invention should preferably contain a gamma'/gamma' proportion of more than 1.3, preferably more than 1.5. Thanks to this combination, yield strengths of over 120 ksi can also be achieved.

Calculations/tests performed

The phases formed in the equilibrium state were calculated for different alloy variants using the JMatPro Thermotech program. The data bank for nickel alloys from Thermotech was used as a database for the calculations. Using the “heat treatment” mode of the JmatPro software, phase contents, particle sizes and expected mechanical properties (e.g., yield strength, tensile strength, hardness) were calculated when a material of the appropriate chemical composition was annealed at different temperatures for age strengthening.

Description of properties

The alloy according to the invention must have, in addition to excellent resistance to hydrogen embrittlement, the following properties:

• good strength

• good resistance to corrosion cracking and pitting

• good phase stability

• good processing ability.

In the nickel-chromium-aluminium-iron-titanium-niobium system, different phases can be formed at different alloy contents, for example, gamma', gamma', delta and eta phases. Tables 3.1 and 3.2 show the results of calculations of the equilibrium fractions of the first calculated chemical compositions. All calculations were performed for an aging hardening temperature of 790°C.

Chemical compositions LV1, 8, 9 and 39 are examples of alloys not in accordance with the present invention.

Based on the above results, calculations of the proportions of equilibrium phases were carried out depending on temperature for other chemical compositions of interest. To determine the temperature at which the precipitates are optimized and therefore enhanced mechanical properties are achieved, calculations were carried out with different age-hardening temperatures. The calculation results are shown in Table 4 and Fig. 5 for chemical composition LB250643. For chemical composition LB250643, 690°C is the peak temperature.

Table 4. Precipitation of phases and corresponding mechanical properties according to the age-hardening temperature in the model alloy Chemical
compound
charge
LB 250643 C 0.01 N 0.005 Cr 18.47 Ni 53.68 Mo 3.05 Ti 1.22 Nb 3.51 Fe* 19.32 P 0.003 Al 0.62 B 0.004 Ta 0.01 Co 0.01 Cu 0.01 Mn 0.01 Si 0.02

Aging hardening 650°C/6h 670°C/6h 690°C/6h 710°C/6h 730°C/6h 750°C/6h Temperature 650 670 690 710 730 750 Yield strength [ksi] 144 158 164 159 154 146 Tensile strength [ksi] 192 202 206 203 200 194 Hardness [Rockwell] 37 40 41 40 39 38 γ' [%] 12 13 13 12 12 eleven γ' size (nm) 17.66 18.38 18.34 18.41 18.72 19.54 γ'' [%] 3.14 4.31 4.16 4.00 3.80 3.57 γ'' size (nm) 11.45 13.62 18.21 23.76 31.42 40.61 Fraction γ'/γ'' 3.82 3.02 3.13 3.00 3.16 3.08

Similar calculations were carried out for all other chemical compositions (diagrams in Fig. 11a - 11ab). To determine the optimal temperature of the secretions, experiments were carried out using different increasing temperatures.

It should be noted that the calculated temperature may deviate from the experimental temperatures.

Properties at other chemical compositions of interest are given along with their peak temperatures in Tables 5.1, 5.2 and 5.3.

If necessary, the alloy can be produced and used in powder form. Since with additive manufacturing methods the machinability of the alloy does not play a role, the chemical composition shows the presence of a wide gap in aluminum content. For additive manufacturing methods, the powder can have a higher aluminum content, reaching 4%. Possible chemical compositions for powder alloy are given in Table 6.

Table 5.3. Chemical compositions, mechanical properties and fractions of precipitation phases in alloy variants at peak temperature (3rd part) Elements LB P01 LB P02 LB P03 LB P04 LB P05 LB P06 C 0.011 0.011 0.011 0.011 0.011 0.011 N 0.005 0.005 0.005 0.005 0.005 0.005 Cr 18.5 18.5 18.5 18.5 18.5 18.5 Ni 54 54 54 54 54 54 Mo 3.05 3.05 3.05 3.05 3.05 3.05 Ti 0.95 0.95 0.95 0.95 0.95 0.95 Nb 5 3.5 5 3.5 5 4.2 Fe* rest rest rest rest rest rest P 0.003 0.003 0.003 0.003 0.003 0.003 Al 1.2 1.2 1.8 1.8 1.5 1.2 B 0.002 0.002 0.002 0.002 0.002 0.002 Ta 0.01 0.01 0.01 0.01 0.01 0.01 Co 0.01 0.01 0.01 0.01 0.01 0.01 Cu 0.01 0.01 0.01 0.01 0.01 0.01 Mn 0.01 0.01 0.01 0.01 0.01 0.01 Si 0.03 0.03 0.03 0.03 0.03 0.03 Peak temp. [°C] 690 690 690 670 690 690 YS [ksi] 172 134 142 88 163 158 TS[ksi] 212 186 191 152 206 202 Hardness
[by Rockwell] 42 36 37 25 41 40 Gamma' [%] 16.41 17.34 24.62 24.03 20.83 16.31 Gamma'' [%] 6.2 1.7 2.5 0 5.0 4.2 Fraction γ'/γ'' 2.66 10.02 9.77 100 4.21 3.88

Table 6. Possible powder compositions Elements LB P07 LB P08 LB P09 LB P10 LB P11 LB P12 LB P12 LB P12 C 0.011 0.011 0.011 0.011 0.011 0.011 0.011 0.011 N 0.012 0.012 0.012 0.012 0.012 0.012 0.012 0.012 Cr 18.5 18.5 18.5 18.5 18.5 18.5 18.5 18.5 Ni 54 54 54 54 54 54 54 54 Mo 3.05 3.05 3.05 3.05 3.05 3.05 3.05 3.05 Ti 0.95 0.95 0.95 0.95 0.95 0.95 0.95 0.5 Nb 5 4.2 3.5 5 4.2 3.5 3.5 3.5 Fe* ost. ost. ost. ost. ost. ost. ost. ost. P 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 Al 2.5 2.5 2.5 3.5 3.5 3.5 4 4 B 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 Ta 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 Co 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 Cu 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 Mn 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 Si 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02

According to the results of these calculations, by increasing the niobium content from about 3.5 to 5%, the proportion of the gamma phase can be doubled if the titanium and aluminum contents are kept constant. If the aluminum and niobium (tantalum) contents are kept constant and the titanium content increases, more gamma phase will be formed and an improvement in mechanical properties is expected. As aluminum content increases, more gamma phase may be released in combination with equal or less titanium and niobium content (compared to Alloy 718).

With an extremely low niobium (tantalum) content (<1%) and a constant aluminum content (≈0.6%), the gamma phase is not formed and therefore, according to calculations, the mechanical properties are not satisfactory.

Fluctuations in the content of molybdenum, tungsten, boron and phosphorus do not have a direct and significant effect on the release of gamma’ and gamma’ phases.

In fig. 5, 6 show phase diagrams showing the release of the gamma phase at temperatures below 919°C and the gamma phase at temperatures below 880°C with the chemical composition LB250643 (with a high content of titanium and aluminum in combination with a low content of niobium (tantalum)) .

The phase diagram in Fig. Figure 5 shows the calculation of the formation of precipitation phases at temperatures below 919°C and takes into account only thermodynamic stability. Therefore, this phase diagram does not take into account the gamma phase. The delta phase is the thermodynamically most stable phase of the release, but due to the kinetics of the release it forms slowly. The content of this phase at this composition is essentially absent according to thermodynamic calculations.

The TTT (time, temperature, conversion) diagram for the chemical composition of LB250643 is shown in Fig. 6. In this case, the presence of the gamma phase is now taken into account. As expected, the delta and this phases precipitated after longer annealing at the age-hardening temperature, therefore, the precipitation of these phases is affected by the duration of annealing during age-hardening. Although no difference was observed between numerical tensile tests of the gamma/delta system with and without the presence of hydrogen, the overall performance at the gamma/delta phase boundaries may be critical due to the low atomic bond energy. Therefore, the duration of annealing during aging hardening should be limited to no more than 60 hours to prevent the formation of the delta phase.

The content of boron and phosphorus does not affect the proportion of gamma' or gamma' phases. Changing the content of aluminum, niobium (tantalum) and titanium directly affects the formation of gamma’ and gamma’ phases.

To understand the quantitative formation of age-hardening phases, calculations were carried out in relation to the chemical composition of LB250643. Calculations for the appropriate chemical composition were carried out at a temperature of the first stage of aging hardening of 650°C (below the peak temperature). After this, a second stage of aging strengthening was carried out at varying temperatures. Similar calculations were performed at the peak temperature as the first stage age hardening temperature and at 730°C (above the peak temperature) as the first stage age hardening temperature, with the second stage temperature varied in 20 degree increments. The results are shown in Table 7 and FIG. 7.

It should be noted that the duration of aging hardening affects the phase fractions. An example for the chemical composition of LB250643 is shown in FIG. 8. This figure shows the isothermal diagram for a given chemistry during age hardening at 650°C, with the maximum gamma phase being reached after about 7 hours. If the temperature is raised to 730°C, then the duration to achieve the maximum proportion of the gamma phase is reduced. In fig. Figure 9 shows an isothermal diagram for a given chemical composition for aging strengthening at 730°C.

The difference between calculated and experimental peak temperatures is expected and known. In order to know what deviation would occur at given composition limits, the peak temperature was confirmed through heat treatment and hardness testing. A diagram with experimentally determined hardness indicators for the chemical composition of LB250643 is shown in Fig. 10. For a given chemical composition, the deviation is 80°C; this difference must be taken into account when planning heat treatment.

Table 7. Proportion of aging strengthening phases and mechanical properties after different two-stage aging strengthening for composition LB250643 Temperature at stage 1 650 650 650 650 650 650 650 650 Temperature at stage 2 550 570 590 610 630 670 690 710 γ’ after stage 1 (%) 12 12 12 12 12 12 12 12 Size γ’ after stage 1 (nm) 19 19 19 19 19 18 18 19 γ’ after stage 2 (%) 1.8 2.4 2.2 2.1 1.9 1.4 1.1 0.8 Size γ’ after 2nd stage (nm) 19 19 19 19 19 18 18 19 γ’’ after stage 1 (%) 3.1 3.1 3.1 3.1 3.1 3.1 3.1 3.1 Size γ'' after stage 1 (nm) 12 12 13 13 14 19 23 28 γ'' after stage 2 (%) 0.6 0.9 1.2 1.5 1.4 1.2 1.0 0.9 Size γ’’ after stage 2 (nm) 12 12 13 13 14 19 23 28 Yield strength (ksi) 156 159 161 162 163 167 163 158 Tensile strength (ksi) 201 203 204 205 205 208 205 202 Hardness (Rockwell) 39 40 40 40 40 41 40 40 Total gamma’ 32.3 33.2 32.9 32.7 32.5 31.9 31.6 31.4 Total gamma'' 15.9 16.4 17.1 17.8 18.5 22.8 26.9 32.4 Proportion γ’/γ’’ 2,040 2,023 1,918 1.843 1,759 1,397 1.172 0.968 Temperature at stage 1 690 690 690 690 690 690 690 690 Temperature at stage 2 530 550 570 590 610 630 650 670 γ’ after stage 1 (%) 13 13 13 13 13 13 13 13 Size γ’ after 1st stage (nm) 19 19 19 19 19 19 19 19 γ’ after stage 2 (%) 1.1 1.4 1.3 1.1 0.9 0.9 0.5 0.3 Size γ’ after 2nd stage (nm) 19 19 19 19 19 19 19 19 γ’’ after stage 1 (%) 4.2 4.2 4.2 4.2 4.2 4.2 4.2 4.2 Size γ'' after stage 1 (nm) 19 19 19 19 19 20 21 23 γ'' after stage 2 (%) 0.2 0.4 0.5 0.5 0.5 0.4 0.3 0.1 Size γ’’ after stage 2 (nm) 19 19 19 19 19 20 21 23 Yield strength (ksi) 175 176 176 176 174 172 169 165 Tensile strength (ksi) 213 214 215 214 213 211 209 207 Hardness (Rockwell) 42 42 42 42 42 42 41 40 Total gamma’ 32.9 33.4 33.2 32.9 32.7 32.6 32.1 31.9 Total gamma'' 23.0 23.3 23.6 23.7 23.8 24.2 25.1 27.1 Proportion γ’/γ’’ 1.433 1.434 1.406 1,388 1.373 1,348 1.278 1.178 Temperature at stage 1 730 730 730 730 730 730 730 730 Temperature at stage 2 570 590 610 630 650 670 690 710 γ’ after stage 1 (%) 12 12 12 12 12 12 12 12 Size γ’ after stage 1 (nm) 20 20 20 19 19 19 19 19 γ’ after stage 2 (%) 2.0 1.8 1.7 1.5 1.3 1.0 0.7 0.4 Size γ’ after 2nd stage (nm) 20 20 20 19 19 19 19 19 γ'' after stage 1 (%) 3.8 3.8 3.8 3.8 3.8 3.8 3.8 3.8 Size γ'' after stage 1 (nm) 32 33 33 33 33 34 35 38 γ’’ after stage 2 (%) 0.3 0.5 0.6 0.7 0.6 0.5 0.4 0.2 Size γ'' after stage 2 (nm) 32 33 33 33 33 34 35 38 Yield strength (ksi) 167 167 167 166 165 162 159 154 Tensile strength (ksi) 208 208 208 208 207 205 202 199 Hardness (Rockwell) 41 41 41 41 41 40 40 39 Total gamma’ 33.7 33.4 33.2 33.0 32.7 32.3 32.0 31.9 Total gamma'' 36.4 36.9 37.5 37.9 37.8 38.2 39.4 41.9 Proportion γ’/γ’’ 0.924 0.905 0.885 0.870 0.864 0.846 0.813 0.760

Experimental data

To confirm the mechanisms of hydrogen embrittlement, laboratory experiments were carried out with laboratory melts with the chemical compositions LB250646, LB250647, LB250650, LB250642. Slow loading tests with cathodic polarization were performed on these melts according to NACE publication 3948, 2014. The results are shown in Table 8.

Table 8. Slow loading test results using 4 chemistries (LB250646 comparative, LB250647 Nb free, LB250650 Al free, LB250642 Low Nb) Compound Test condition Sample No. Elongation at break Time before breakup Rm (%) Coefficient, (%) min Coefficient, (%) MPa Coefficient, (%) LB250646 Inert environment A1 20.3 - 4657 - 1109 - Aggressive environment A2 13.2 65 3295 71 1118 101 Aggressive environment A3 13.2 65 3448 74 1092 98 Aggressive environment A4 13 64 3375 72 1062 96 Average 65 72 98 LB250647 Inert environment IN 1 40.9 - 9098 - 535 - Aggressive environment AT 2 44.9 110 9283 102 586 110 Aggressive environment AT 3 44.8 110 9442 104 487 91 Aggressive environment AT 4 43 105 9039 99 513 96 Average 108 102 99 LB250650 Inert environment C1 17.8 - 4222 - 1108 - Aggressive environment C2 9.3 52 2524 60 1094 99 Aggressive environment C3 10 56 2450 58 1088 98 Aggressive environment C4 7.8 44 2055 49 1038 94 Average 51 55 97 LB250642 Inert environment D1 30.5 - 6343 - 973 - Aggressive environment D2 28.4 93 5934 94 937 96 Aggressive environment D3 26.2 86 5838 92 882 91 Aggressive environment D4 31 102 6213 98 895 92 Average 94 95 93

Slow loading tests support the theoretical mechanism that the presence or predominance of gamma' is detrimental to the resistance of a material to hydrogen embrittlement, since alloys with no or low niobium content (i.e., gamma-dominant) do not have all or have almost no susceptibility to hydrogen embrittlement, which is confirmed by higher elongation coefficients at break.

The charge providing only gamma release (LB250650 without aluminum content) is characterized by the worst resistance to hydrogen embrittlement.

Therefore, the stated limits for the alloy according to the invention can be separately justified as follows.

Iron reduces cost and thus should be used. Therefore, 12% is the lower limit for iron content. However, iron should not be added excessively due to the deterioration of the material properties. Therefore, 24% should be considered the upper limit. If necessary, iron can be replaced with cobalt.

A minimum of 17% chromium increases strength at room temperature while providing overall corrosion resistance. When combined with carbon, chromium carbides are formed, which can increase strength at high temperatures. Too high chromium contents impair the phase stability of the alloy and promote the formation of harmful phases, which negatively affects ductility and toughness, and therefore a chromium content of 21% serves as an upper limit.

Higher molybdenum contents increase resistance to pitting corrosion in chlorine-containing environments. As the minimum molybdenum content increases from 0.001 to 3%, resistance to corrosion cracking at elevated temperatures also increases. The upper limit is considered to be 9% content, since the addition of molybdenum significantly affects the cost of the metal.

Tungsten can be used as a replacement element for molybdenum and is then also limited to a content of >0 to 9%.

A combination of molybdenum and tungsten is also possible, with the tungsten proportion set to at least 0.01%.

The formation of the intermetallic gamma phase released during aging hardening increases with increasing amount of Al + Ti. Therefore, a minimum aluminum content of 0.4% is necessary. If the aluminum content is too high, then aggregation and coarsening of the gamma phase occurs along the grain boundaries, as a result of which the mechanical properties sharply decrease and hot workability deteriorates. For a powder alloy for additive manufacturing methods, the aluminum content can be set higher, since the corresponding processes do not involve hot deformation. Therefore, the aluminum content is limited to 4.0%.

Titanium is combined with aluminum and nickel to produce the gamma phase, which helps increase the strength of the alloy as a result of the precipitates. However, if titanium is added in excessive quantities, this phase can form, which causes the mechanical properties to deteriorate. Therefore, titanium is added in amounts up to 3.0%.

Niobium (or tantalum) stabilizes the gamma phase and helps increase strength. Therefore, its minimum content should be 1%. However, niobium (or tantalum) is involved in the formation of the gamma phase, which is detrimental to hydrogen embrittlement resistance and should therefore be controlled. For this reason, the niobium (or tantalum) content is limited to between 1 and 5.7%.

Boron and phosphorus have the ability to suppress excessive accumulation of hydrogen along phase and grain boundaries. This can reduce sensitivity to hydrogen embrittlement. However, phase and grain boundary segregations are too pronounced when boron and phosphorus are applied in excess, and the effect of reducing hydrogen embrittlement is lost. Processability may also be limited and therefore boron is limited to from 0.001% to not more than 0.01%, phosphorus is limited to from 0.001 to not more than 0.02%.

Cobalt can replace nickel; it improves properties at elevated temperatures. The alloy may contain up to 3% cobalt.

The carbon content is limited to no more than 0.045%, since this element at this content reduces the workability due to excessive formation of carbides.

Copper is limited to no more than 0.23%, since this element reduces oxidation resistance.

The rest of the alloy is nickel (50 - 55%), it should be borne in mind that the remainder contains small amounts of impurities that do not significantly change the properties of the alloy. Therefore, impurities such as sulfur may be present in a total amount of 0.01%. Manganese and silicon are limited to a content not exceeding 0.35%.

Heat treatment planning is essential to control and model phase precipitation. Therefore, the limits of the heat treatment parameters of the alloy according to the invention can be justified separately as follows.

Precipitation phases for possible limits of chemical composition are formed at temperatures below 970°C and therefore the alloy is subjected to solid solution annealing for from 0.1 min to 60 hours in order to transfer all phases into solution, taking into account the size of the product. The solution annealing temperature is limited to a maximum value of 1150°C in order to limit grain growth. To eliminate the formation of precipitates after annealing on a solid solution, it is proposed to carry out rapid cooling in a moving annealing atmosphere, inert gas, water, polymer or oil.

Ag hardening annealing is then carried out to form precipitation phases and to achieve good mechanical properties. To do this, the material is annealed at a temperature of 600 to 900°C for 0.1 hour to 60 hours. Longer periods of age hardening lead to precipitation of delta and eta phases and should be avoided.

If necessary, aging hardening can be carried out in the second stage at a temperature of 550 to 900°C for from 0.1 hour to 60 hours.

The aging hardening temperature is selected depending on the purpose. Age strengthening processes that optimize mechanical properties are used in applications where superior mechanical properties are required. Aging strengthening processes that optimize the gamma/gamma phase ratio are used in applications where superior resistance to hydrogen embrittlement is required.

Single-stage aging strengthening results in higher gamma'/gamma' phase ratios and lower mechanical properties.

Two-stage aging strengthening can result in different structures achieving different mechanical properties depending on the selected temperatures in the first and second stages.

If the temperature in the first stage is equal to the mentioned peak temperature, then the aging hardening results in superior mechanical properties, although the gamma'/gamma' phase ratio is calculated to be lower.

Two-stage aging strengthening at the first temperature above the peak temperature results in average mechanical properties. The ratios of the proportions of gamma’/gamma’ phases are smaller in this case, i.e. this results in lower resistance to hydrogen embrittlement.

If the temperature in the first stage is below the peak temperature, and the temperature in the second stage is less than the temperature in the first stage, then the mechanical properties will be lower than those that can be achieved with single-stage age strengthening. However, the ratio of gamma'/gamma' phase fractions can be higher, and thus such heat treatment can be used in applications where the main goal is increased requirements for resistance to hydrogen embrittlement. On the other hand, excellent mechanical properties can also be achieved when the temperature in the first stage is below the peak temperature and the temperature in the second stage is higher than the first temperature. The ratio of the proportions of gamma’ / gamma’ phases remains at the same level.

The duration of aging hardening must also be taken into account. Low temperature age strengthening requires longer periods of age strengthening so that all precipitation can occur, while for higher temperature age strengthening short periods of age strengthening are sufficient.

The following properties can be achieved by the alloy according to the invention or by the heat treatment according to the invention (solution annealing and age hardening annealing): acid gas elongation at break (NACE Publication 3948) greater than 75%, preferably greater than 90% , with a yield strength in air >100 ksi, preferably >120 ksi.

Brief description of drawings

Fig. 1 - energy depending on elongation during a numerical tensile test of the gamma/gamma’ system without (black line) and with (red line) the presence of a hydrogen atom.

Fig. 2 - energy depending on stretching during a numerical tensile test of the gamma/gamma system without (black line) and with (red line) a hydrogen atom.

Fig. 3 - energy depending on stretching during a numerical tensile test of the gamma/delta system without (black line) and with (red line) a hydrogen atom.

Fig. 4 - images of the material obtained by scanning electron microscope, represented by variants 120K, 140K, 150K of the Alloy 718 alloy.

Fig. 5 - mechanical properties depending on the temperature of aging hardening of the alloy of composition LB250643.

Fig. 5’ - phase diagram of the alloy composition LB250643

Fig. 6 - diagram “time, temperature, transformation” of the alloy of composition LB250643.

Fig. 7 - calculated mechanical properties after two-stage hardening by aging hardening of the alloy of chemical composition LB250643.

Fig. 8 - isothermal diagram of the alloy of the chemical composition LB250643 during hardening by aging at 650°C. The fraction of the gamma phase is shown by red circles, the fraction of the gamma phase is shown by blue quadrangles.

Fig. 9 - isothermal diagram of the alloy of the chemical composition LB250643 during hardening by aging at 730°C. The fraction of the gamma phase is shown by red circles, the fraction of the gamma phase is shown by blue quadrangles.

Fig. 10 - experimental curve of hardness depending on the temperature of hardening by aging of an alloy of the chemical composition LB250643.

Fig. 11a-11ab - mechanical properties depending on the temperature of aging hardening of different alloy variants.

Claims (45)

1. Method for producing powder from a nickel alloy containing, wt.%: Ni: 50 – 55 Cr: 17 – 21 Mo: > 0 – 9 W: 0 – < 9 Nb: 1 – < 5.7 Ta: > 0 – 4.7 Ti: 0.1 – 3.0 Al: 0.4 – 4.0 Co: no more than 3.0 Mn: no more than 0.35 Si: no more than 0.35 Cu: no more than 0.23 C: 0.001–0.045 S: no more than 0.01 P: 0.001 – 0.02 B: 0.001 – 0.01 the rest is Fe and the usual production-related impurities, when the following relations are met: Nb + Ta: >1 – 5.7 … (1) Al + Ti: >1.2 – 5 … (2) Mo + W: 3 – 9 … (3), where Nb, Ta, Al, Ti, Mo and W are the content of the corresponding elements in wt.%, including: - smelting the alloy in a vacuum induction (VIM) furnace, - holding the melt for 5 minutes to 2 hours for homogenization, - installation in a closed spray unit with gas supply, dew point from -10 to 120°C, - injection of the melt through a nozzle into the gas flow at a gas flow rate from 2 m ³ /min to 150 m ³ /min, - collecting hardened powder particles in a hermetically sealed container, while particle size ranges from 5 to 250 microns, the powder particles are spherical, the powder contains gas inclusions with a pore area of more than 0.0 to 4% (pores > 1 μm) of the total surface of the objects being assessed, the apparent density of the powder ranges from 2 to the density of the alloy, which is 8 g/cm ³ , - sealed packaging of the powder in a protective gas atmosphere containing argon. 2. The method according to claim 1, characterized in that the chromium content is 17-20 wt.%, preferably 17-19 wt.%. 3. Method according to claim 1 or 2, characterized in that the content of molybdenum and/or tungsten is 3-8 wt.%, preferably 3-7 wt.%. 4. Method according to any one of paragraphs. 1–3, characterized in that it has the following relationship between niobium and tantalum: Nb + Ta = 2–4.5 wt.%, in particular, Nb + Ta = 2–4 wt.%, where Nb and Ta are the content of the corresponding elements in wt.%. 5. Method according to any one of paragraphs. 1–4, characterized in that the titanium content is 0.5-3.0 wt.%, preferably 1.0-3.0 wt.%, more preferably 1.0-2.0 wt.%. 6. Method according to any one of paragraphs. 1–5, characterized in that the aluminum content is 0.6-2.5 wt.%, preferably 0.6-2.0 wt.%, more preferably 0.6-1.5 wt.%. 7. Method according to any one of paragraphs. 1–6, characterized in that the carbon content is from 0.001 to not more than 0.035 wt.%, preferably from 0.001 to not more than 0.025 wt.%. 8. Method according to any one of paragraphs. 1–7, characterized in that it has the following ratio between aluminum and titanium: Al + Ti = 1.4 – 4 wt.%, preferably Al + Ti = 1.6 – 4 wt.%, where Al and Ti are the content of the corresponding elements in wt.%. 9. Application of a method for producing powder from a nickel alloy according to any one of claims. 1–8 for the manufacture of a product in the form of rod, wire, strip, sheet, longitudinally welded pipe or seamless pipe. 10. Application of a method for producing powder from a nickel alloy according to any one of claims. 1–8 for the production of structural elements for the oil and gas industry or for the chemical industry.