RU2607857C1 - Method of producing electrodes from nickel aluminide-based alloys - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to special metallurgy, in particular to production of cast charge workpieces of electrodes from highly doped nickel aluminide-based alloys, and can be used for centrifugal atomization of electrode material and production of granules for use in addition 3D technologies in order to obtain complex-shape articles from refractory metal materials. Method of producing electrodes from nickel aluminide-based alloy includes production of semi-finished product by centrifugal SHS casting at centrifugal acceleration 60±10 g using a reaction mixture containing, wt%: nickel oxide 47.0–49.1, aluminium 28.6–32.4, mixture Cr₂O₃, Hf, B and Co₃O₄ as dopant 13.1–17.9, mixture Al₂O₃ and Na₃AlF₆ as functional additive 6.5–7.0, and further two-step remelting of semi-finished product to produce at first step a refined degassed ingot, and at second step – an electrode, wherein second step 2–3 minutes before pouring into melt, an ingot is added, consisting of pressed mixture of aluminium with modifying nanopowder with specific surface area 5÷30 m²/g and lumped aluminum, in an amount which provides content in melt of 0.5–7 vol% nanopowder, with further cooling to room temperature and extraction electrode from crystallizer. MoO₃ is further added to mixture of dopant, modifying additive used in nanopowder is powder of one of WC, TaC, NbC, ZrO₂, Y₂O₃, Al₂O₃.

EFFECT: technical result of proposed invention is developing integrated technology of producing electrodes from nickel aluminide-based alloys.

5 cl, 3 ex, 10 tbl, 10 dwg

Description

The invention relates to the field of special metallurgy, in particular to the production of cast electrodes from highly alloyed alloys based on nickel aluminides, and can be used for centrifugal atomization of the electrode material, which can be used to obtain granules used in additive 3D technologies for the production of complex products from heat resistant metal materials.

A known method (RU 2032496, publ. 10.04.1995) for producing transition metal aluminides, mainly nickel, tantalum, titanium, niobium, iron, comprising preparing an exothermic mixture of transition metal and aluminum powders, briquetting the mixture, heating the briquettes before initiating the reaction of self-propagating high-temperature synthesis ( SHS) and subsequent hot deformation of the synthesis products.

The disadvantage of this method is the high energy consumption, the high cost of the starting powders of metal reagents, increased requirements for the purity of the starting powders by impurities: oxygen, nitrogen, carbon, etc., which is often difficult to put into practice.

A known method (RU 2523049, publ. 20.07.2014) for producing a cast alloy based on titanium gamma-aluminide, intended for producing shaped castings, comprising obtaining a mixture of pure metal powders containing titanium, aluminum and niobium, obtaining a briquette with a relative density of 50- 85%, thermal vacuum treatment of the briquette at a temperature of 550-650 ° C for 10-40 minutes, a heating rate of 5-40 ° C / min and a pressure of 10 ^-1 -10 ^-3 Pa, and the SHS is carried out at an initial temperature of 560-650 ° C.

A known method for producing heat-resistant alloys (RU 2534325, publ. 11/27/2014), which includes the preparation of a reaction mixture of powders of the starting components containing oxides of Nickel, cobalt, chromium III, molybdenum, titanium, pure aluminum, as well as carbon, boron, zirconium, room the reaction mixture into a refractory form, placing the mold on a centrifuge, igniting the mixture and carrying out synthesis in the combustion mode under centrifugal acceleration of 200-300g followed by separation of the cast alloy based on nickel aluminides, while preparing the mixture with the following components, wt.%: nickel oxide 40.0-43.7, cobalt oxide 12.0-13.2, chromium oxide 2.9-4.3, molybdenum oxide 3.1-3.9, titanium oxide 1 , 3-2.4, carbon, boron and zirconium.

The disadvantage of this method is that it does not allow to obtain long electrodes of a given geometry from a nano-modified alloy.

The closest analogue to the claimed one is the method (CN 100497700 C, publ. 10.06.2009) for producing electrodes from alloys based on nickel aluminides, including multi-stage remelting of segregation-prone alloy components (Ni, Al, Cr, Mo, Ta) to obtain the first stages of refining a degassed ingot, and in subsequent stages, an electrode that is homogeneous in chemical composition. In this case, remelting is carried out in a protective inert atmosphere or in vacuum.

The disadvantage of this method is the high energy costs associated with multi-stage remelting: the number of remelts varies from 3 to 6 times, increased requirements for the chemical purity of the starting components, the required purity of the starting metals is 99.999% by impurities, which significantly increases the cost of the process and product, as well as the inability to obtain electrodes with a nanomodified structure.

The technical result of the claimed invention is to reduce energy consumption and cost by reducing the number of remelts to two and using less expensive oxide raw materials while ensuring the chemical purity of the resulting electrode in terms of impurities, namely: oxygen less than 0.2%, nitrogen less than 0.01%, carbon less than 0.1%. In addition, the technical result is to increase the heat resistance of the obtained electrode by reducing the grain size of the main phase NiAl of the electrode material by nanomodification of this material.

The technical result of the claimed invention is achieved as follows.

A method of producing electrodes from alloys based on nickel aluminide involves the preparation of a semi-finished product by centrifugal SHS casting with centrifugal acceleration of 60 ± 10 g using a reaction mixture containing, wt.%:

Nickel oxide 47.0-49.1 Aluminum 28.6-32.4 A mixture of Cr ₂ O ₃ , Hf, B and Co ₃ O ₄ as an alloying agent 13.1-17.9 A mixture of Al ₂ O ₃ and Na ₃ AlF ₆ as a functional additive 6.5-7.0

Then, a two-stage remelting of the semi-finished product is carried out to obtain a refined degassed ingot in the first stage, and an electrode in the second stage. At the same time, in the second stage, a ligature is introduced into the melt 2–3 minutes before casting, consisting of a pressed mixture of aluminum with a modifying nanopowder with a specific surface area of 5–30 m ² / g and lump aluminum, in an amount ensuring a content of 0.5- 7 vol.% Nanopowder. Then the melt is cooled to room temperature and removed from the crystallizer.

Centrifugal SHS casting is carried out by placing the reaction mixture in a refractory form coated on the inner surface with a functional protective layer of a refractory inorganic compound, setting the mold on a centrifuge, igniting the mixture, carrying out the SHS process and separating the synthesized cast alloy from slag.

MoO ₃ is additionally added to the dopant mixture.

The two-stage remelting of the semi-finished product is carried out in a protective inert atmosphere or in vacuum.

As a modifying nanopowder, WC, or TaC, or NbC, or ZrO ₂ , or Y ₂ O ₃ , or Al ₂ O _{3 is used} .

The invention is illustrated by drawings, where in FIG. 1 and in FIG. 2 shows the appearance of ingots synthesized under the stated optimal conditions; FIG. 3 and FIG. 4 shows the microstructure of alloys synthesized under optimal conditions; FIG. 5 shows the appearance of an ingot synthesized under non-optimal conditions; FIG. 6 and in FIG. 7 shows the microstructures of an alloy synthesized outside predetermined parameters; FIG. 8 shows an external view of a centrifugal installation with a refractory curb mold placed on the rotor; FIG. 9 shows the appearance of the final synthesis products after extraction from the mold; FIG. 10 shows the appearance of an electrode of a nanomodified heat-resistant alloy based on NiAl.

The invention is as follows.

The synthesis stage of the cast semi-finished product by centrifugal SHS casting is carried out by preparing the reaction mixture from aluminum, nickel oxide, alloying and functional additives. The mixture is loaded into a refractory mold coated with a functional protective layer of a refractory inorganic compound from the inner surface, the mold is placed on the centrifuge rotor, the mixture is ignited, and synthesis is carried out in the combustion mode under centrifugal acceleration of 60 ± 10 g. In this case, the reaction mixture is prepared in the following ratio of components, wt.%: Nickel oxide - 47.0-49.1; aluminum - 28.6-32.4; alloying additive - 13.1-17.9; functional additive - 6.5-7.0. As a dopant, a mixture of components Cr ₂ O ₃ and Hf and B and Co ₃ O _{4 is used} . An additional MoO ₃ component is added to the dopant.

In addition, functional additives Al ₂ O ₃ and Na ₃ AlF ₆ with a total content of not more than 7.0 wt.% Are introduced into the composition of the initial exoteric mixture.

The subsequent stage of processing the semi-finished product includes a two-stage induction remelting in a protective inert atmosphere or in vacuum. At the first stage, refining and degassing of the ingot is carried out. At the second stage, the nanomodification of the alloy is carried out by introducing into the melt a ligature consisting of a pressed mixture of aluminum with a modifying nanopowder with a specific surface of 5-30 m ² / g and lump aluminum, in an amount providing a content of 0.5-7 vol.% Nanopowder in the melt , 2-3 minutes before casting and its subsequent casting into the mold of a given geometry. Then the melt is cooled to room temperature and removed from the crystallizer.

Reducing the cost, reducing the number of remelting to two and using less expensive oxide raw materials while ensuring the chemical purity of the resulting electrode in terms of impurities, namely: oxygen less than 0.2%, nitrogen less than 0.01%, carbon less than 0.1% is achieved due to the use of energy-saving SHS-casting technology, which allows to synthesize in the combustion mode a highly pure impurity semi-finished product with a liquid-free structure, from which it is subsequently possible to obtain an electrode with the required tour and cleanliness.

An increase in the heat resistance of the obtained electrode is achieved by introducing the optimal amount of WC, ZrO ₂ , Y ₂ O ₃ nanoparticles, which significantly (2–3 times) grind the grain of the main NiAl phase.

The choice of the initial mixture, including a high content of Al, nickel oxide and dopants, such as Cr ₂ O ₃ , Hf, B, Co ₃ O ₄ , MoO ₃ , the introduction of functional additives Al ₂ O ₃ and Na ₃ AlF ₆ into the mixture for regulation viscosity of the slag phase, the establishment of centrifugal acceleration of 60 ± 10g allows you to get high-alloy heat-resistant alloys based on nickel aluminides with non-aliquot structure.

The subsequent two-stage remelting allows to reduce the content of gas impurities to values less than 0.4%, to carry out nanomodification of the alloy by introducing ligatures with nanosized particles into the melt, and to form long electrodes by casting the alloy into a mold of a given geometry.

The introduction of a dopant allows you to provide:

1) solid solution (Co, Mo) hardening of the matrix material (based on NiAl);

2) composite hardening of the matrix by precipitates based on the complex boride compound Ni ₂₀ Al ₃ B ₆ and CrB with partial replacement of Ni and Cr by Mo;

3) the Hf and B components are structural modifiers and have a positive effect on the formation of a fine-grained, non-liquid structure of the developed compositions.

When the content of the mixture components in the claimed range and the overload value of 60 ± 10g are formed, non-porous ingots (Fig. 1 and Fig. 2) with structural components evenly distributed over the volume (Fig. 3 and Fig. 4).

The choice of centrifugal acceleration of 60 ± 10g is due to the optimization of the synthesis process, aimed at the maximum possible increase in the mass of the synthesized ingot. The range of overload values is due to the total effect aimed at obtaining the maximum possible volume of combustion, taking into account the characteristics of the centrifugal unit and the maximum yield (phase separation depth) of the target phase (metal) in the ingot.

In the case of deviations from the specified intervals, the content of NiO components is 47.0-49.1, Al 28.6-32.4, dopants 13.1-17.9, functional additives 6.5-7.0, as well as the effects of an overload below 50 g, a discontinuity is formed in the synthesized ingots, observed both at the macro level (Fig. 5) and at the micro level (Fig. 6 and Fig. 7). Examples to justify the modes of SHS-centrifugal casting and remelting are summarized in table. 1-9.

With a total dopant content of more than 17.9% (Example 7, Table 2), numerous lamellar precipitates of complex monoborides Mo (V, Cr) B and ceramic inclusions based on corundum are formed in the alloy structure, which reduces the ductility and heat resistance of the obtained materials. In the case of a dopant content below 13.1% (Example 6, Table 2), an alloy with increased brittleness is formed, which cannot be used in a two-stage remelting of electrodes for centrifugal atomization of granules.

The combined effect of alloying and functional additives, as well as the optimal choice of the range of centrifugal effects (60 ± 10g) on the synthesis process ensures the maximum yield of the target product (alloy) in the ingot and the formation of a non-liquid structure. With the non-optimal choice of composition and the effect of overload (Example 6, 7, Table 3), a sharp decrease in the depth of phase separation (up to 86-82%) is observed, which significantly reduces the efficiency of the claimed method for producing a semi-finished product.

When a ligature consisting of a pressed mixture of aluminum with a modifying nanopowder is introduced, less than 2 minutes before the melt is poured into the crystallizer, the nanoparticles do not have time to evenly distribute over the melt volume, which leads to structural heterogeneity of the ingot and a large grain size dispersion. With an increase in the time spent by the nanoparticles in the melt for more than 3 min before casting into the crystallizer, they dissolve in the case of carbides WC, TaC, NbC or agglomerate in the case of oxides ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , which also does not give the desired effect of modification alloy structure.

When the concentration of the modifying nanopowder in the melt is less than 0.5 vol.%, There is no noticeable modification of the structure of the ingot, and an increase in the concentration of the nanopowder more than 7 vol.% Is impractical, because the melt viscosity increases, its fluidity worsens, and further grinding of the grains of structural components does not occur.

The range of specific surface area of the modifying nanopowder is also experimentally justified 5-30 m ² / g. At a specific surface of less than 5 m ² / g, powders of submicron size do not have a noticeable modifying effect on the structure of the ingot. The choice of a nanosized powder with a specific surface of more than 30 m ² / g leads to a negative result for several reasons: agglomeration of nanoparticles in the case of oxide compounds or dissolution of nanoparticles in a melt in the case of carbide compounds.

The two-stage remelting of the semi-finished product is carried out in a protective inert atmosphere or in vacuum to prevent oxidation of the melt and increase the service life of the furnace units.

Example 1 (table. 2, example 1)

To obtain a cast semi-finished product, powders are taken: nickel oxide, molybdenum oxide, chromium oxide, cobalt oxide, aluminum oxide, aluminum, hafnium and boron. The main characteristics of the reagents are given in table. one.

The reaction mixture is prepared in the following ratio of components, wt.%: Nickel oxide - 47.5; aluminum - 32.4; alloying additive - 13.1; functional additive - 7.0. As an alloying additive, powders are used, wt.%: MoO ₃ - 0.6, Cr ₂ O ₃ - 5.4, Co ₃ O ₄ - 5.7, Hf - 1.3, B - 0.1. As a functional additive, powders are used, wt.%: Al ₂ O ₃ - 6.4 and Na ₃ AlF ₆ - 0.6.

The finished mixture is placed in a graphite form, coated from the inner surface with a protective refractory layer of a refractory inorganic compound based on corundum. The mold is placed on the centrifuge rotor, the mixture is locally ignited using a tungsten helix and synthesis is carried out in the combustion mode with a centrifugal acceleration of 70g.

After completion of the SHS process, the product is cooled and removed from the mold. The product is a two-layer ingot (Fig. 9): the upper layer is an oxide solution (slag) based on corundum, the lower layer is the target product is a heat-resistant alloy based on nickel aluminides. The yield of the target product (an alloy based on nickel aluminides) is 98% of the calculated value. The grain size of the main NiAl phase is 10-20 microns. The synthesized alloy contains, wt.%: Nickel - 58.8; aluminum - 27.0; molybdenum - 0.7; chromium - 5.8; cobalt - 6.6; boron - 0.1; hafnium - 1.0. The content of gas impurities is, wt.%: Oxygen - 0.110, nitrogen - 0.0012, carbon - 0.078. The grain size of the main NiAl phase is 10-20 microns.

To process the semi-finished product, a two-stage remelting is carried out in a protective inert atmosphere. At the first stage, remelting is carried out by refining the semi-finished product in an induction furnace by melting in a periclase crucible at a temperature of 1680-1700 ° C in an atmosphere of high-grade argon (99.995% Ar), which fills the chamber of the induction furnace after pumping to diffusion vacuum (10 ^-5 Pa) at a pressure of 0.95 × 10 ⁵ Pa. The induction heating rate is 150 ± 30 ° C / min. To remove gaseous impurities, the obtained melt is maintained at a temperature of 1680-1700 ° C for 3 minutes. The casting of the obtained melt is carried out with the inductor turned on in a graphite crucible with a diameter of 50-100 mm, previously installed in the furnace chamber, in which the ingot crystallizes. At the end of the casting process, the inductor is turned off. The resulting ingot from a heat-resistant alloy based on NiAl is cooled in the chamber of an induction furnace in an argon atmosphere for 3-5 hours.

At the second stage of remelting, a homogenizing induction remelting of the obtained ingot is carried out with additional alloying with lumpy A99 grade aluminum (to compensate for aluminum evaporated during refining remelting) and aluminum powder ligatures based on nanosized WC particles. Ligatures are added to the melt through a vacuum lock in the furnace chamber in an amount providing 1 vol.% Nanopowder and 26.3 ± 0.5% aluminum in the alloy. Mixtures for the manufacture of ligatures are obtained in a planetary ball mill with a gravity factor of at least 90 g by mixing aluminum powder of grade PA-4 with nanosized particles in a ratio of 3: 1 by weight, diameter of grinding bodies 3-5 mm, mass ratio of balls: material = 10 : 1, processing time 5 minutes. Compact powder ligature is obtained by cold pressing in a steel mold with a diameter of 20-50 mm with a load of 3-5 t / cm ² , which provides a relative density of 0.7-0.9.

Remelting is carried out under the following conditions: pressure Ar - 0.95 × 10 ⁵ Pa, temperature - 1680-1700 ° С, heating rate - 150 ± 30 ° С / min. For the purpose of homogenization, the obtained melt is maintained at a temperature of 1680-1700 ° C for 2 minutes, which ensures uniform distribution of the nanomodifier over the alloy volume. The casting of the obtained melt is carried out with the inductor turned on in a graphite crucible with a diameter of 50-100 mm with a thermally insulated profitable part with a height of 15-25% of the electrode height. The obtained electrode is cooled in the chamber of an induction furnace in an argon atmosphere for 3-5 hours. After cooling, the electrode is removed from the mold, the surface is cleaned of the remains of the mold, and the profitable part is cut off. The appearance of the electrode is shown in FIG. 10.

The resulting electrode contains in its composition (table. 4), wt.%: Nickel - 57.0; aluminum - 26.5; molybdenum - 0.7; chrome 5.6; cobalt - 6.4; boron - 0.1; hafnium - 1, nanophase WC - 2.66.

The resulting electrode is tested for heat resistance by the following method. The electrode is placed in a muffle furnace preheated to a temperature of 1000 ° C, kept in it for 20 minutes, after which it is removed from the furnace onto a chamotte lined surface, on which it is cooled in air to room temperature. After this, the electrode is re-aged for 20 minutes in an oven at 1000 ° C, then it is removed from the oven and cooled in air to room temperature. Heat resistance tests on the heating-cooling cycle are carried out until the detection of delamination cracks. A satisfactory number of cycles is considered to be more than 10, which allows predicting sufficient resistance to thermal shock during plasma centrifugal spraying.

Impurity content: oxygen - 0.132%, nitrogen - 0.006%, carbon - 0.082%. The grain size of the main phase is NiAl = 40-50 μm, residual porosity = 0.5%, heat resistance was 22 cycles, no shells and delays were detected.

Example 2 (table. 2, example 3)

For the synthesis of cast semi-finished product, by analogy with example 1, the reaction mixture is prepared in the following ratio of components, wt.%: Nickel oxide - 49.1; aluminum - 30.5; alloying additive - 13.6; functional additive - 6.8. As an alloying additive, powders are used, wt.%: MoO ₃ - 5.8, Cr ₂ O ₃ - 3.6, Co ₃ O ₄ - 2.7, Hf - 1.2, B - 0.3. As a functional additive, powders are used, wt.%: Al ₂ O ₃ - 5.0 and Na ₃ AlF ₆ - 1.8.

The finished mixture is placed in graphite form, coated from the inner surface with a functional protective layer of a refractory inorganic compound based on corundum. The mold is placed on the centrifuge rotor, the mixture is locally ignited using a tungsten helix, and synthesis is carried out in the combustion mode with a centrifugal acceleration of 60 g.

After completion of the combustion process, the synthesis product is cooled and removed from the mold. The combustion product is a two-layer ingot: the upper layer is an oxide solution (slag) based on corundum, the lower layer is the target product is a heat-resistant alloy based on nickel aluminides. The yield of the target product of the alloy based on nickel aluminides is 95% of the calculated value. The synthesized alloy contains, wt.%: Nickel - 62.0; aluminum - 23.3; molybdenum - 6.2; chrome 3.9; cobalt - 3.2; boron - 0.4; hafnium - 1.0. The content of gas impurities is, wt.%: Oxygen - 0.130, nitrogen - 0.0013, carbon - 0.085. The grain size of the main phase of NiAl is 30-40 microns.

To process the semi-finished product, by analogy with example 1, a two-stage remelting is carried out in a protective inert atmosphere. At the first stage, the semi-finished product is refined in an induction furnace by melting in a periclase crucible at a temperature of 1680-1700 ° С in an atmosphere of high-grade argon (99.995% Ar), which fills the chamber of the induction furnace after pumping to diffusion vacuum (10 ^-5 Pa), at a pressure of 0.95 × 10 ⁵ Pa. The induction heating rate is 150 ± 30 ° C / min. To remove gaseous impurities, the obtained melt is maintained at a temperature of 1680-1700 ° C for 3 minutes. The casting of the obtained melt is carried out with the inductor turned on in a graphite crucible with a diameter of 50-100 mm, previously installed in the furnace chamber, in which the ingot crystallizes. At the end of the casting process, the inductor is turned off. The resulting ingot from a heat-resistant alloy based on NiAl is cooled in the chamber of an induction furnace in an argon atmosphere for 3-5 hours.

At the second stage, a homogenizing induction remelting of the obtained ingot is carried out with additional alloying with lumpy aluminum of grade A99 to compensate for aluminum evaporated during refining remelting and with powder alloys based on aluminum with nanosized ZrO ₂ particles. Ligatures are added to the melt through a vacuum shutter in the furnace chamber in an amount providing 3 vol.% Nanopowder and 26.1 ± 0.5% aluminum in the alloy. Mixtures for the manufacture of ligatures are obtained in a planetary ball mill with a gravity factor of at least 90 g by mixing aluminum powder of grade PA-4 with nanosized particles in a ratio of 3: 1 by weight, diameter of grinding bodies 3-5 mm, mass ratio of balls: material = 10 : 1, processing time 5 minutes. Compact powder ligature is obtained by cold pressing in a steel mold with a diameter of 20-50 mm with a load of 3-5 t / cm ² , which provides a relative density of 0.7-0.9. Remelting is carried out under the following conditions: pressure Ar - 0.95 × 10 ⁵ Pa, temperature - 1680-1700 ° С, heating rate - 150 ± 30 ° С / min.

For the purpose of homogenization, the obtained melt is maintained at a temperature of 1680-1700 ° C for 3 minutes, which ensures uniform distribution of the nanomodifier over the alloy volume. The casting of the obtained melt is carried out with the inductor turned on in a graphite crucible with a diameter of 50-100 mm with a thermally insulated profitable part with a height of 15-25% of the electrode height. The obtained electrode is cooled in the chamber of an induction furnace in an argon atmosphere for 3-5 hours. After cooling, the electrode is removed from the mold, the surface is cleaned of the remains of the mold, and the profitable part is cut off.

The resulting electrode contains in its composition, wt.%: Nickel - 56.9; aluminum - 25.7; molybdenum - 6.1; chrome 3.8; cobalt - 3.1; boron - 0.4; hafnium - 1; nanophase - 2.9.

Impurity content: oxygen - 0.987%, nitrogen - 0.09%, carbon - 0.121%. The grain size of the main phase is NiAl = 10-20 μm, residual porosity = 0.5%, heat resistance = 18 cycles, no shells and delays were detected.

Example 3 (table. 2, example 5)

For the synthesis of cast semi-finished product (by analogy with example 1), the reaction mixture is prepared in the following ratio of components, wt.%: Nickel oxide - 47.0; aluminum - 28.6; alloying additive - 17.9; functional additive - 6.5. As an alloying additive, powders are used, wt.%: MoO ₃ - 12.4, Cr ₂ O ₃ - 2.9, Co ₃ O ₄ - 0.3, Hf - 1.1, B - 1.2. Powders, wt.%: Al ₂ O ₃ - 3,5 and Na ₃ AlF ₆ - 3,0 are used as a functional additive.

The finished mixture is placed in graphite form, coated from the inner surface with a functional protective layer of a refractory inorganic compound based on corundum. The mold is placed on the centrifuge rotor, the mixture is locally ignited using a tungsten helix, and synthesis is carried out in the combustion mode with a centrifugal acceleration of 50 g.

After completion of the combustion process, the synthesis product is cooled and removed from the mold. The combustion product is a two-layer ingot: the upper layer is an oxide solution (slag) based on corundum, the lower layer is the target product is a heat-resistant alloy based on nickel aluminides. The yield of the target product (an alloy based on nickel aluminides) is 94.0% of the calculated value. The synthesized alloy contains in its composition (table. 3), wt.%: Nickel - 61.4; aluminum - 16.6; molybdenum - 15.8; chrome 3.2; cobalt - 0.3; boron - 1.7; hafnium - 1.0. The content of gas impurities is, wt.%: Oxygen - 0.17, nitrogen - 0.0017, carbon - 0.098. The grain size of the main NiAl phase is 40-50 microns.

For the processing of semi-finished products (by analogy with example 1), a two-stage remelting is carried out in a protective inert atmosphere. At the first stage, the semi-finished product is refined in an induction furnace by melting in a periclase crucible at a temperature of 1680-1700 ° С in an atmosphere of high-grade argon (99.995% Ar), which fills the chamber of the induction furnace after pumping to diffusion vacuum (10 ^-5 Pa), at a pressure of 0.95 × 10 ⁵ Pa. The induction heating rate is 150 ± 30 ° C / min. To remove gaseous impurities, the obtained melt is maintained at a temperature of 1680-1700 ° C for 3 minutes. The casting of the obtained melt is carried out with the inductor turned on in a graphite crucible with a diameter of 50-100 mm, pre-installed in the furnace chamber, in which the ingot crystallizes. At the end of the casting process, the inductor is turned off. The resulting ingot from a heat-resistant alloy based on NiAl is cooled in the chamber of an induction furnace in an argon atmosphere for 3-5 hours.

At the second stage, a homogenizing induction remelting of the obtained ingot is carried out with additional alloying with lumpy aluminum of grade A99 (to compensate for the aluminum evaporated during refining remelting) and with powder alloys based on aluminum with nanosized particles of Y ₂ O ₃ . Ligatures are added to the melt through a vacuum lock in the furnace chamber in an amount providing 5 vol.% Nanopowder and 25.4 ± 0.5% aluminum in the alloy. Mixtures for the manufacture of ligatures are obtained in a planetary ball mill with a gravity factor of at least 90 g by mixing aluminum powder of grade PA-4 with nanosized particles in a ratio of 3: 1 by weight, diameter of grinding bodies 3-5 mm, mass ratio of balls: material = 10 : 1, processing time 5 minutes. Compact powder ligature is obtained by cold pressing in a steel mold with a diameter of 20-50 mm with a load of 3-5 t / cm ² , which provides a relative density of 0.7-0.9. Remelting is carried out under the following conditions: pressure Ar - 0.95 × 10 ⁵ Pa, temperature - 1680-1700 ° С, heating rate - 150 ± 30 ° С / min.

For the purpose of homogenization, the obtained melt is maintained at a temperature of 1680-1700 ° C for 2.5 minutes, which ensures uniform distribution of the nanomodifier over the alloy volume. The casting of the obtained melt is carried out with the inductor turned on in a graphite crucible with a diameter of 50-100 mm with a thermally insulated profitable part with a height of 15-25% of the electrode height. The obtained electrode is cooled in the chamber of an induction furnace in an argon atmosphere for 3-5 hours. After cooling, the electrode is removed from the mold, the surface is cleaned of the remains of the mold, and the profitable part is cut off.

The resulting electrode contains in its composition, wt.%: Nickel - 49.4; aluminum - 25.7; molybdenum - 14.6; chrome 3.1; cobalt - 0.3; boron - 1.6; hafnium - 1, nanophase (Y ₂ O ₃ ) - 4.3.

Impurity content, wt.%: Oxygen - 0.974, nitrogen - 0.022, carbon - 0.096%. The grain size of the main phase is NiAl = 10-20 μm, residual porosity = 1.2%, heat resistance = 14 cycles, no shells and delays were detected.

The composition and properties of the synthesized alloys according to the examples presented in table. 2.

In the table. 4 shows the compositions and properties of the electrodes obtained by two-stage remelting of the SHS semi-finished product according to example 1 of the table. 3, when using WC nanopowder with a specific surface of 16 m ² / g, the time before casting is 2.5 minutes.

In the table. 5 shows the compositions and properties of the electrodes obtained by two-stage remelting of the SHS semi-finished product according to example 1 of the table. 3, the specific surface of the ZrO ₂ nanopowder is 18 m ² / g, the time to casting is 2.5 min.

In the table. 6 shows the compositions and properties of the electrodes obtained by two-stage remelting of the SHS semi-finished product according to example 1 of the table. 3, the specific surface of the nanopowder Y ₂ O ₃ 21 m ² / g, the time before casting 2.5 minutes

In the table. 7-8 shows the compositions and properties of the electrodes obtained by two-stage remelting of the SHS semi-finished product according to example 1 of the table. 3, with the specific surface of the nanosupplement WC 16 m ² / g (table. 7), nanoparticles ZrO ₂ 18 m ² / g (table. 8).

In the table. 9-10 shows the compositions and properties of the electrodes obtained by two-stage remelting of the SHS semi-finished product according to example 1 of the table. 3, at a time before casting the melt into the mold 2.5 minutes

Thus, the combination of features claimed in the formula allows one to obtain cast electrodes from highly alloyed nanomodified alloys based on nickel aluminides, which can be used for plasma centrifugal spraying of granules and their subsequent application in additive 3D technologies of sophisticated products from heat-resistant metallic materials.

An example of obtaining an electrode in a known manner according to the prototype (CN 100497700)

The mixture is prepared from high-purity components in the form of fused bars and ingots with a content of the main component of not less than 99.999% in quantity, wt.%: Nickel 58.8; aluminum 27.0; molybdenum 0.7; chrome 5.8; cobalt 6.6; boron 0.1; hafnium 1.0.

For processing, a three-stage remelting is carried out in a protective inert atmosphere. At the first stage, refining the charge in the induction furnace is carried out by melting in a periclase crucible at a temperature of 1680-1700 ° C in an atmosphere of high-grade argon (99.995% Ar), which fills the chamber of the induction furnace after pumping to diffusion vacuum (10 ^-5 Pa), at a pressure of 0.95 × 10 ⁵ Pa. The induction heating rate is 150 ± 30 ° C / min. To remove gaseous impurities, the obtained melt is maintained at a temperature of 1680-1700 ° C for 3 minutes. The casting of the obtained melt is carried out with the inductor turned on in a graphite crucible with a diameter of 50-100 mm, previously installed in the furnace chamber, in which the ingot crystallizes. At the end of the casting process, the inductor is turned off. The obtained ingot is cooled in the chamber of an induction furnace in an argon atmosphere for 3-5 hours.

At the second stage, the first homogenizing induction remelting of the obtained ingot is carried out with additional alloying with lumpy aluminum of grade A99 (to compensate for the aluminum evaporated during refining remelting). Remelting is carried out at a pressure of Ar - 0.95 × 10 ⁵ Pa, a temperature of 1680-1700 ° C, a heating rate of 150 ± 30 ° C / min. In order to homogenize the resulting melt is maintained at a temperature of 1680-1700 ° C for 2 minutes. Casting of the obtained melt is carried out with the inductor turned on in a graphite crucible with a diameter of 50-100 mm. The obtained ingot is cooled in the chamber of an induction furnace in an argon atmosphere for 3-5 hours. After cooling, the ingot is removed from the mold, the surface is cleaned of the remains of the mold.

At the third stage, a second homogenizing induction remelting of the obtained ingot is carried out at an Ar pressure of 0.95 × 10 ⁵ Pa, a temperature of 1680-1700 ° C, a heating rate of 150 ± 30 ° C / min. The melt is maintained at the achieved temperature for 2 minutes. The casting of the obtained melt is carried out with the inductor turned on in a graphite crucible with a diameter of 50-100 mm with a thermally insulated profitable part with a height of 15-25% of the electrode height. The cooling of the obtained electrode ingot is carried out in the chamber of an induction furnace in an argon atmosphere for 3-5 hours. After cooling, the electrode is removed from the mold, the surface is cleaned of the remains of the mold, and the profitable part is cut off. The appearance of the electrode is similar to FIG. 10. The resulting fused electrode contains a predetermined number of alloying components, wt.%: Nickel 58.8; aluminum 27.0; molybdenum 0.7; chrome 5.8; cobalt 6.6; boron 0.1; hafnium 1.0. The content of impurities, wt.%: Oxygen - 0.105, nitrogen - 0.008, carbon - 0.063, residual porosity = 0.4%, heat resistance = 5 cycles, shells and stratifications were not detected. The prototype method provides high chemical purity and uniformity of the electrode, although the grain size of the main phase of NiAl reaches 250-280 microns.

In comparison with the proposed method, the presence of three stages of remelting increases 1.4 times the energy consumption, and the use of high-purity components for stitching increases the cost of the electrode as a whole by more than 1.5 times. In this case, the coarse-grained electrode exhibits less heat resistance, and there is a high probability of its destruction during centrifugal spraying.

Thus, the combination of features claimed in the formula allows to obtain cast electrodes from highly alloyed nanomodified alloys based on nickel aluminides, which can be used for centrifugal sputtering and subsequent use in complex 3D technologies of complex products made from heat-resistant metallic materials.

Claims (7)

1. A method of producing electrodes from an alloy based on nickel aluminide, including the preparation of a semi-finished product by centrifugal SHS casting with centrifugal acceleration of 60 ± 10 g using a reaction mixture containing, wt.%: nickel oxide 47.0-49.1 aluminum 28.6-32.4 mixture of Cr ₂ O ₃ , Hf, B and Co ₃ O ₄ as an alloying agent 13.1-17.9 a mixture of Al ₂ O ₃ and Na ₃ AlF ₆ as a functional additive 6.5-7.0, and the subsequent two-stage remelting of the semi-finished product to obtain a refined degassed ingot in the first stage and an electrode in the second stage, and in the second stage, a ligature consisting of a pressed aluminum mixture with a modifying nanopowder with a specific surface of 5 is introduced into the melt 2-3 times before casting ÷ 30 m ² / g and lump aluminum, in an amount providing a melt content of 0.5-7 vol.% Nanopowder, followed by cooling to room temperature and removing the electrode from the mold. 2. The method according to p. 1, in which centrifugal SHS casting is carried out by placing the reaction mixture in a refractory form coated on the inner surface with a functional protective layer of a refractory inorganic compound, setting the mold on a centrifuge, igniting the mixture, carrying out the SHS process and separating the synthesized cast alloy from slag. 3. The method according to p. 1, in which MoO ₃ is additionally introduced into the mixture of the dopant. 4. The method according to p. 1, in which the two-stage remelting of the semi-finished product is carried out in a protective inert atmosphere or in vacuum. 5. The method according to p. 1, in which the powder of WC, or TaC, or NbC, or ZrO ₂ , or Y ₂ O ₃ , or Al ₂ O _{3 is} used as a modifying nanopowder.

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