CN110079702B - Ni-Cr-based alloy and preparation method thereof - Google Patents

Abstract

The invention provides a Ni-Cr-based alloy and a preparation method thereof. In the Ni-Cr-based alloy, the mass percentage of Cr is 35-45%, V is 0.1-3%, Co is 0.1-0.5%, La The alloy preparation method of the present invention cooperates with a certain heat treatment system and gradient strong magnetic field conditions, and changes the shape of the discontinuous precipitation phase on the basis of changing the solute enrichment and migration law at the grain boundary. Nucleation growth conditions provide a driving force for the competitive nucleation growth and control of DP/CP, inhibit the effect of discontinuous precipitation of Ni-Cr-based superalloys, and obtain Ni-Cr-based Ni-Cr-based superalloys with high strength and high thermal creep resistance. Superalloy.

Description

A kind of Ni-Cr-based alloy and preparation method thereof

technical field

The invention relates to a high-strength and high-temperature creep resistance Ni-Cr-based superalloy and a preparation method thereof, belonging to the technical field of alloy preparation.

Background technique

Due to its excellent high temperature strength, thermal creep resistance and oxidation resistance, Ni-Cr alloys are widely used in extreme environments such as chemical, petrochemical, and nuclear industries, as well as in electric furnaces, household appliances, far-infrared devices, magnetron sputtering, etc. Coating and other equipment core components. The study found that Ni-Cr-based alloys with a chromium content of 35%-45% will form discontinuous precipitates at the grain boundaries after low temperature aging treatment, and continuous precipitates will be formed in their grains after high temperature aging treatment. As the temperature decreases, the solubility of Cr in Ni decreases sharply to form Cr-based precipitates with different morphology including discontinuous and/or continuous precipitation. Phases usually have an adverse effect on the creep resistance and mechanical properties of superalloys due to sudden changes in structure and composition. Therefore, it is of great theoretical and practical value to explore and study the α precipitates that inhibit the discontinuous precipitation morphology in Ni-Cr-based superalloys, improve their properties, and expand the application range.

Chinese invention patent 106676331A proposes a high temperature resistant nickel-chromium alloy strip, the composition of which is Cr: 19.0-21.0%, Mo: 8.0-9.0%, Co: 9.0-11.0%, Ti: 1.9-2.3%, Al: 1.3- 1.7%, C: 0.02 to 0.10%. The preparation process is smelting-hot forging-hot rolling-solid solution pickling-cold rolling-annealing. At 750°C, the tensile strength is 750-800MPa, and the elongation is 25%-30%. Chinese invention patent 1974816A proposes a high temperature resistant nickel-chromium alloy, the composition of which is Cr: 21-25%, Ni: 58-63%, Al: 1.0-1.7%, and the balance is Fe. The preparation process is smelting-hot working-cold working. Its yield strength is 315MPa, and its tensile strength is 705MPa. The content of Cr in the Ni-Cr-based alloys of the above Chinese invention patents is below 25%, and the precipitation strengthening mechanism of Cr is not fully utilized, which is not conducive to the further improvement of the high-temperature performance of Ni-Cr alloys. In view of this, the patent of the present invention proposes a Ni-Cr alloy with higher than 25% Cr, in order to further improve its high strength and high temperature creep properties.

Discontinuous Precipitation (DP, also known as cellular precipitation) refers to the desolubilization and decomposition of α supersaturated solid solution at the grain boundary to form an α' phase with the same structure as the α matrix and a β phase with different structural components from the matrix. It usually nucleates at the grain boundaries in a cellular shape, and grows and coarsens as the grain boundaries move. This type of phase transformation is usually accompanied by continuous precipitation (CP), and has been found in many types of precipitation-strengthening materials such as copper-based, magnesium-based, aluminum-based and superalloys. Essentially, there is competition between CP and DP, the formation of DP will reduce the supersaturation of the matrix to reduce the driving force for nucleation of CP; the formation of CP will also reduce the supersaturation, and the formation of CP will pinning Migration of high-angle grain boundaries required for DP growth, which in turn reduces the generation of DP. Therefore, inhibiting the nucleation of DP precipitates by promoting the nucleation and growth of CP is an important method to improve such materials.

The growth of α-Cr discontinuous precipitation phase is controlled by the diffusion of Cr at the grain boundary, and the thermodynamic interaction between the added elements and Cr causes different diffusion at the grain boundary. Among them, the addition of Cu can promote the growth of DP, and the addition of W and Mo can help to reduce the DP. However, the addition of Fe and Co had no significant effect on the growth of DP. Therefore, by adding elements to change the nucleation and growth conditions of DP and CP, to promote the formation of CP and inhibit the nucleation and growth of DP, it will help to improve the performance of the material.

SUMMARY OF THE INVENTION

The purpose of the present invention is to propose a high-strength, high thermal creep performance Ni-Cr-based superalloy and the same for the problem that the existing technology cannot fully utilize the precipitation strengthening effect of Cr, which is not conducive to the further improvement of the high-temperature performance of the Ni-Cr alloy. The preparation method is to add V, Co, La, etc., the third component that suppresses the nucleation of discontinuous precipitation phases to the Ni-Cr-based superalloy, and cooperates with a certain heat treatment system and gradient strong magnetic field conditions to change the solute at the grain boundary. On the basis of enrichment and migration laws, changing the nucleation and growth conditions of discontinuous precipitation phase provides a driving force for the competitive nucleation growth and control of DP/CP, and inhibits the effect of discontinuous precipitation of Ni-Cr-based superalloys, thereby A Ni-Cr-based superalloy with high strength and high thermal creep resistance is obtained.

One aspect of the present invention provides a high-strength and high-temperature creep Ni-Cr-based alloy prepared by the above method, wherein the composition and composition of the Ni-Cr-based alloy are: the mass percentage of Cr is 35-45%, and V is 0.1 to 3%, Co is 0.1 to 0.5%, La is 0.1 to 0.5%, and the balance is Ni.

Based on the above technical solutions, preferably, the mass percentage of Cr is 40-42%, V is 1-2%, Co is 0.2-0.3%, La is 0.1-0.3%, and the balance is Ni.

One aspect of the present invention provides a method for preparing a Ni-Cr-based alloy with high strength and high thermal creep, comprising the following process steps:

(1) Preparation of alloy ingots: Add raw materials with a purity of ≥99.9wt% into the smelting equipment in proportion, and apply a low-frequency electromagnetic stirring effect of 1.5-5Hz during the smelting process to make the smelting and stirring process more uniform. Under the protection of standard atmospheric pressure inert atmosphere, Ni-Cr-based alloy ingots are cast;

(2) Hot rolling, cold rolling and solution treatment: the Ni-Cr-based alloy ingot obtained in step (1) is subjected to hot rolling at 1000-1200°C, and then cold-rolled with a pass reduction of 50-90%. After the treatment, solution treatment is carried out at 1100 to 1250° C. for 1 to 6 hours.

(3) Aging treatment in strong magnetic field: place the solution-treated ingot obtained in step (2) in a strong magnetic field of 0.1 to 45 T, adjust the position of the sample, and under a gradient strong magnetic field of -800 T ² /m to 800 T ² /m (including 0T ² /m), at a temperature of 500 to 700° C., quenching after heat preservation for 0.5 to 12 hours to obtain a Ni-Cr-based alloy.

The "gradient magnetic field" in the present invention refers to a strong magnetic field having a magnetic induction gradient along the axial or radial direction. In particular, in the present invention, the product of the magnetic induction and the magnetic induction gradient is used to define the size and difference of the "gradient magnetic field", that is, The alloy sample is subjected to magnetizing forces under this "gradient magnetic field". In particular, the magnetic induction intensity B is selected to be parallel to the direction of gravity, and there is a gradient gradB along this direction. At this time, the "gradient magnetic field" is represented by B·grad B.

In the above technical solution, preferably the inert atmosphere is nitrogen or argon, and the pressure is 0.25-0.75 standard atmosphere.

In the above technical scheme, the preferred smelting equipment is a high-vacuum arc smelting furnace, a vacuum induction furnace or a vacuum consumable smelting furnace; when a high-vacuum arc smelting furnace is used, the ingot casting method is suction casting, and a vacuum induction furnace or vacuum consumable is used. In the smelting furnace, the ingot casting method is casting.

In the above technical solution, the hot rolling conditions are preferably 1150-1200°C.

In the above technical solution, the cold rolling conditions are preferably such that the pass reduction is 50-90%, more preferably 60-80%, and most preferably 65-75%.

In the above technical solution, the solution treatment time is preferably 1 to 6 hours, more preferably 1 to 3 hours, and most preferably 1.5 to 2 hours.

In the above technical solution, the sample obtained by solution treatment is preferably placed in a magnetic field of 0.1-30T, more preferably 1-12T, and most preferably 8-10T.

In the above technical solution, the aging temperature of the strong magnetic field is preferably 550-650°C, more preferably 550-600°C, and most preferably 575-600°C.

In the above technical scheme, the Ni-Cr-based alloy is preferably subjected to a strong magnetic field aging treatment under a gradient magnetic field (including 0T ² /m) of -450T ² /m to 450T ² /m, more preferably -425T ² /m to 425T ² /m, most preferably -350T ² /m to 350T ² /m.

In the above technical solution, it is preferred that after the high magnetic field aging treatment, the temperature is kept for 0.5 to 6 hours and then quenched, more preferably for 1 to 5 hours, and most preferably for 2 to 4 hours.

Further, the Ni-Cr-based alloy is suction cast in a high vacuum electric arc furnace under the protection of 0.25-0.75 standard atmospheric pressure argon or nitrogen; or using a vacuum induction melting furnace under the protection of 0.25-0.75 standard atmospheric pressure argon or nitrogen. Cast in copper molds or other metal molds.

Further, the Ni-Cr-based alloy is prepared by the following method: according to the mass percentage of the target Ni-Cr-based alloy composition, electrolytic Ni sheets, Cr sheets and La blocks, V blocks and Co blocks with a purity of ≥99.9wt% are used and other metal raw materials, the Ni-Cr-based alloy is prepared by suction casting after high vacuum arc melting or casting in a metal mold for melting in a vacuum induction furnace or similar smelting methods.

Another aspect of the present invention provides a high-strength and high-temperature creep Ni-Cr-based alloy prepared by the above method, wherein the composition and composition of the Ni-Cr-based alloy are: the mass percentage of Cr is 35-45%, V It is 0.1 to 3%, Co is 0.1 to 0.5%, La is 0.1 to 0.5%, and the balance is Ni.

beneficial effect

(1) The presence of high-density Cr-rich precipitates in Ni-Cr-based alloys with a content of 35%-45% Cr can strengthen the matrix and further improve the high-temperature performance of the alloy.

(2) During the melting process, a low-frequency electromagnetic field of 1.5-5 Hz is applied, and the alloy is stirred by electromagnetic force formed by the low-frequency electromagnetic field and the melt movement, which can achieve more uniform solute distribution and temperature distribution of the alloy, and can obtain higher quality alloy casting. ingot.

(3) The preparation method of the present invention applies a gradient magnetic field to control the law of solute enrichment and migration at grain boundaries. Since the magnetic moment of the matrix is different from that of the precipitation phase, a strong magnetic field can be used to control the nucleation, growth, and phase transition of the precipitation phase in the solid-state phase transition. Change kinetics, grain boundary and interface energy, etc., change the structure characteristics and properties of materials, and comprehensively control the high-temperature strength and high-temperature thermal creep of Ni-Cr-based alloys.

(4) Compared with the Ni-Cr-based alloy prepared in the prior art, the thermal creep property of the Ni-Cr-based alloy prepared by the present invention is increased by 18-25% under the condition that the high temperature strength is basically not reduced. Among them, the effect of the composition of the present invention is remarkable, and the thermal creep property of the existing Ni-Cr-based alloy can be improved by 18% to 20%.

Description of drawings

1 is a microstructure diagram of the Ni-Cr alloy prepared in Example 1.

FIG. 2 is a microstructure diagram of the Ni-Cr alloy prepared in Comparative Example 1. FIG.

Detailed ways

The following non-limiting examples may enable those of ordinary skill in the art to more fully understand the present invention, but do not limit the present invention in any way.

The test methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials can be obtained from commercial sources unless otherwise specified.

The model of the high vacuum electric arc furnace used in the embodiment of the present invention is ZFH-300-70.

The model of the vacuum induction melting furnace used in the embodiment of the present invention is TG100A-25.

The embodiment of the present invention adopts JMTD-12T100 superconducting magnet.

In the embodiment of the present invention, JSD-20T52 superconducting magnet is used.

In the embodiment of the present invention, a 45T high-strength hybrid magnet is used.

The model of the vacuum heat treatment furnace used in the embodiment of the present invention is VHT-II.

In the embodiment of the present invention, the SANS-CMT5105 electronic universal testing machine is used to test the stress-strain curve and obtain the tensile strength.

In the embodiment of the present invention, a TMT-D5 high temperature creep testing machine is used to test the high temperature creep resistance.

A preferred embodiment of the present invention is:

(1) Preparation of master alloy: Use high-purity metals such as Ni, Cr, La, V, and Co with a purity of ≥99.9wt%, and use vacuum induction furnace or vacuum consumable melting furnace or similar melting equipment to smelt the metal. In the smelting process, low-frequency electromagnetic stirring at 1.5-5 Hz is applied, and Ni-Cr-based alloy ingots are prepared by casting in a copper mold or similar mold under the protection of 0.1-1 standard atmosphere of argon.

(2) Hot rolling, cold rolling and solution treatment: the Ni-Cr-based alloy obtained in step (1) is subjected to hot rolling treatment at 1150-1200°C, and then cold-rolled with a pass reduction of 67-75%. , carry out solution treatment at 1100-1250 ℃ for 1.5-2h.

(3) Aging treatment in strong magnetic field: place the sample obtained in step (2) in a strong magnetic field of 8 to 10 T, adjust the position of the sample, and under a gradient strong magnetic field of -350 T ² /m to 350 T ² /m (including 0 T ² /m ), at a temperature of 575 to 600 °C, quenching after holding for 2 to 4 hours to obtain a Ni-Cr-based alloy.

Example 1

(1) Preparation of master alloy: Ni, Cr, La, V, Co high-purity metals with a purity of ≥99.9wt% are used, and the metals are smelted in a vacuum induction furnace. In the smelting process, low-frequency electromagnetic stirring at 1.5 Hz was applied, and Ni-35%Cr-3%V-0.5%Co-0.5%La alloy ingots were prepared by casting in a copper mold under the protection of 0.1 standard atmosphere of argon.

(2) Hot rolling, cold rolling and solution treatment: the Ni-Cr-based alloy obtained in step (1) is subjected to hot rolling treatment at 1150 °C, and then cold rolling with a pass reduction of 50%, and then processed at 1100 °C. Solution treatment was carried out for 6 h.

(3) Aging treatment in strong magnetic field: place the sample obtained in step (2) in a 0.1T strong magnetic field, adjust the position of the sample, and under the gradient strong magnetic field of 0T ² /m, at a temperature of 700 °C, after holding for 0.5 hours Quenching to obtain Ni-Cr-based alloys.

The prepared Ni-35%Cr-3%V-0.5%Co-0.5%La alloy has a tensile strength of 850MPa at 750℃, and a creep bending life of 5000h at 800℃ and 750MPa at high temperature.

Comparative Example 1

The preparation process of the alloy is the same as that of Example 1, the composition is changed to Ni-35%Cr, and the rest of the treatment is the same as that of Example 1. The tensile strength of the prepared Ni-35%C alloy at 750 ° C is 800 MPa, and at high temperature of 800 ° C, the tensile strength is 800 MPa. The 800MPa creep bending life is 4100h.

It can be seen that the tensile strength of the Ni-35%Cr-3%V-0.5%Co-0.5%La alloy obtained in Example 1 of the present invention is 5% higher than that of the Ni-35%Cr alloy in the comparative example at 750°C, and the high temperature Creep resistance improved by 18%.

Figure 1 is the microstructure diagram of the Ni-Cr alloy prepared in Example 1. It can be seen from the figure that there are obvious acicular continuous precipitation structures in the crystal; Figure 2 is the microstructure diagram of the Ni-Cr alloy prepared in Comparative Example 1. It can be seen from the figure that there are obvious discontinuous precipitation cells at the grain boundaries. Comparative analysis shows that the addition of V, Co and La elements in the Ni-Cr-based alloy proposed in this patent not only promotes the formation of a high-density continuous Cr-rich precipitation phase, but also inhibits the discontinuous precipitation cell structure at the grain boundary, thereby The improvement of the high temperature performance of the alloy proposed in this patent is achieved.

Example 2

(1) Preparation of alloy ingots: Ni, Cr, La, V, Co high-purity metals with a purity of ≥99.9wt% are used, and the metals are smelted by vacuum induction furnace equipment. During the smelting process, 3Hz low-frequency electromagnetic stirring is applied. Ni-40%Cr-0.1%V-0.1%Co-0.1%La alloy ingots were prepared by casting in a copper mold under the protection of standard atmospheric pressure argon;

(2) Hot rolling, cold rolling and solution treatment: the Ni-Cr-based alloy obtained in step (1) is subjected to hot rolling treatment at 1180 °C, and then cold rolling with a pass reduction of 70%, and then processed at 1150 °C. Solution treatment was carried out for 3 h.

(3) Aging treatment in strong magnetic field: place the sample obtained in step (2) in a strong magnetic field of 23T, adjust the position of the sample, under the gradient strong magnetic field of -800T ² /m, and at a temperature of 600 ° C, after holding for 6 hours Quenching to obtain Ni-Cr-based alloys.

The prepared Ni-40%Cr-0.1%V-0.1%Co-0.1%La alloy has a tensile strength of 900MPa at 750℃, and a creep bending life of 5450h at 800℃ and 750MPa at high temperature.

Comparative Example 2

The preparation process and composition of the alloy are the same as those in Example 2. In step (3), a steady and constant magnetic field is not applied. The rest of the treatment is the same as that in Example 2. The tensile strength of %La alloy at 750℃ is 800MPa, and the creep bending life at 800℃ and 750MPa at high temperature is 4865h.

It can be seen that the tensile strength of the Ni-40%Cr-0.1%V-0.1%Co-0.1%La alloy obtained in Example 2 of the present invention is increased by 11% compared to the alloy in Comparative Example 2, and the high temperature creep resistance is increased by 19%. %.

Example 3

(1) Preparation of alloy ingots: Ni, Cr, La, V, Co high-purity metals with a purity of ≥99.9wt% are used, and the metals are smelted by vacuum induction furnace equipment. During the smelting process, a low-frequency electromagnetic stirring effect of 5Hz is applied. Ni-45%Cr-2%V-0.2%Co-0.3%La alloy ingots were prepared by casting in a copper mold under the protection of standard atmospheric pressure argon;

(2) Hot rolling, cold rolling and solution treatment: the Ni-Cr-based alloy obtained in step (1) is subjected to hot rolling treatment at 1200 °C, and then cold rolling with a pass reduction of 90%, and then processed at 1250 °C. solution treatment for 1 h.

(3) Aging treatment in strong magnetic field: place the sample obtained in step (2) in a strong magnetic field of 45T, adjust the position of the sample, and quench it under the gradient strong magnetic field of 800T ² /m at a temperature of 500°C for 12 hours , to obtain Ni-Cr-based alloys.

The tensile strength of the prepared Ni-45%Cr-2%V-0.2%Co-0.3%La alloy at 750℃ is 955MPa, and the creep bending life at 650℃ and 705MPa at high temperature is 5900h.

Example 4

(1) Preparation of alloy ingots: Ni, Cr, La, V, Co high-purity metals with a purity of ≥99.9wt% are used, and the metals are smelted by vacuum induction furnace equipment. During the smelting process, a low-frequency electromagnetic stirring effect of 5Hz is applied. Ni-45%Cr-2%V-0.2%Co-0.3%La alloy ingots were prepared by casting in a copper mold under the protection of standard atmospheric pressure argon;

(2) Hot rolling, cold rolling and solution treatment: the Ni-Cr-based alloy obtained in step (1) is subjected to hot rolling treatment at 1200 °C, and then cold rolling with a pass reduction of 90%, and then processed at 1200 °C. solution treatment for 1 h.

(3) Aging treatment in strong magnetic field: place the sample obtained in step (2) in a strong magnetic field of 45T, adjust the position of the sample, and quench it under a gradient strong magnetic field of 800T ² /m and a temperature of 500°C for 6 hours , to obtain Ni-Cr-based alloys.

The tensile strength of the prepared Ni-45%Cr-2%V-0.2%Co-0.3%La alloy at 750℃ is 908MPa, and the creep bending life at 650℃ and 705MPa at high temperature is 4425h. The specific embodiment summary results are shown in Table 1.

Table 1

Claims (5)

1. A method for preparing a Ni-Cr-based alloy, characterized in that, in the Ni-Cr-based alloy, the mass percentage of Cr is 35-45%, V is 0.1-3%, and Co is 0.1-0.5%, La is 0.1-0.5%, the balance is Ni, and the preparation method includes the following steps: (1) Preparation of alloy ingot: The raw materials are stirred and smelted in the smelting equipment according to the composition ratio, and a low-frequency electromagnetic of 1.5-5 Hz is applied. After smelting, it is cast in a copper mold under the protection of an inert atmosphere to prepare a Ni-Cr-based alloy. ingot; (2) Hot rolling, cold rolling and solution treatment: the Ni-Cr-based alloy ingot obtained in step (1) is subjected to hot rolling at 1000-1200°C, and then cold-rolled with a pass reduction of 50-90%. treatment to reduce the thickness to less than 5mm, and perform solution treatment at 1100-1250°C for 1-6h; (3) Aging treatment in strong magnetic field: place the ingot after solution treatment in step (2) in a strong magnetic field of 0.1 to 45 T, under a gradient strong magnetic field of -800 T ² /m to 800 T ² /m, at a temperature of 500 Under the condition of ~700°C, quenching after heat preservation for 0.5 to 12 hours to obtain the Ni-Cr-based alloy; The gradient strong magnetic field means that the strong magnetic field has a magnetic induction intensity gradient along the axial or radial direction, and the size and difference of the gradient strong magnetic field are defined by the product of the magnetic induction intensity and the magnetic induction intensity gradient; There is a gradient gradB in the direction, and the gradient strong magnetic field is represented by B·grad B at this time. 2. The method according to claim 1, wherein: in the Ni-Cr-based alloy, the mass percentage of Cr is 40-42%, V is 1-2%, Co is 0.2-0.3%, La is 0.1 to 0.3%, and the balance is Ni. 3. method according to claim 1, is characterized in that: described smelting equipment is high vacuum electric arc melting furnace, vacuum induction furnace or vacuum consumable melting furnace; When adopting high vacuum arc melting furnace, the mode of ingot casting is to absorb smelting furnace. For casting, when a vacuum induction furnace or a vacuum consumable melting furnace is used, the ingot casting method is casting. 4 . The method according to claim 1 , wherein the inert atmosphere in the step (1) is nitrogen or argon at 0.1-1 standard atmospheric pressure. 5 . 5 . The method according to claim 4 , wherein the inert atmosphere is 0.25-0.75 standard atmospheric pressure argon or nitrogen. 6 .

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