Preparation method of copper-nickel-tin alloy capable of improving oxidation resistance

Abstract

The invention discloses a preparation method of a copper-nickel-tin alloy capable of improving oxidation resistance, and relates to the technical field of copper-nickel-tin alloys. Comprising the following steps that high-purity copper powder, nickel powder, tin powder and gallium powder and / or indium powder are subjected to vacuum drying and then placed in a high-energy ball milling tank to be subjected to ball milling under the argon protection effect, then screening is conducted, and evenly-mixed composite powder is obtained; the composite powder is placed in a graphite mold, pre-pressing is conducted through a cold isostatic press, densification treatment is conducted through spark plasma sintering, and a blank block is obtained; the blank block is placed in a vacuum furnace to be subjected to heat treatment, then surface pre-oxidation treatment is conducted, low-melting-point metal gallium and / or indium are / is evenly dispersed and added through a powder metallurgy method, the low-melting-point metal can be liquefied at the high temperature and migrated to oxidation cracks, defects are filled, a new oxidation film is formed, and a liquid-phase self-repairing mechanism is introduced; and the anti-oxidation life is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of copper-nickel-tin alloys, and in particular to a method for preparing a copper-nickel-tin alloy capable of improving oxidation resistance. Background Art

[0002] Copper-nickel-tin alloys offer advantages such as wear resistance, corrosion resistance, high lubricity, and excellent high-temperature stability, making them commonly used as substrates for high-temperature, heavy-load bearings. Furthermore, compared to beryllium bronze, copper-nickel-tin alloys offer lower production costs, are pollution-free, and possess higher strength and hardness, excellent corrosion resistance, and superior machinability. With an operating temperature exceeding 300°C, they are often used as a beryllium copper alternative.

[0003] In the prior art, the improvement of the oxidation resistance of copper-nickel-tin alloy mainly relies on surface treatment technology, but the traditional methods have the following obvious defects: Micro-arc oxidation: Although a ceramic coating can be formed on the alloy surface, the high porosity (>10%) in the process makes it easy for corrosive media to penetrate the substrate, requiring additional sealing treatment (such as phosphating solution post-treatment), which increases the process complexity. Anodizing: Conventional processes consume high energy, and the film uniformity and adhesion are insufficient. It is easy to peel off under high temperature or mechanical stress. For example, the oxide film formed by anodizing CuNi34 alloy is corrosion-resistant, but its long-term stability is limited. Electroplating / chemical plating: Although electroplating nickel or chromium layers can improve corrosion resistance, the coating has weak bonding with the substrate and may introduce environmental pollutants (such as hexavalent chromium). Summary of the Invention

[0004] The object of the present invention is to provide a method for preparing a copper-nickel-tin alloy capable of improving oxidation resistance, so as to at least partially solve the above-mentioned problems.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for preparing a copper-nickel-tin alloy capable of improving oxidation resistance, comprising the following steps: High-purity copper powder, nickel powder, tin powder and gallium powder and / or indium powder are vacuum dried respectively, then placed in a high-energy ball milling tank, ball milled under argon protection, and then sieved to obtain a uniformly mixed composite powder; The composite powder is placed in a graphite mold, pre-pressed by a cold isostatic press, and densified by spark plasma sintering to obtain a green block; The green block is placed in a vacuum furnace for heat treatment and then subjected to surface pre-oxidation treatment.

[0006] Furthermore, the heat treatment includes low-temperature aging heat treatment and medium-temperature stabilization heat treatment: During the low-temperature aging heat treatment, the temperature in the vacuum furnace is adjusted to 240-260°C, and the low-temperature aging treatment time is 2-8 hours; During the medium-temperature stabilization heat treatment, the temperature in the vacuum furnace is adjusted to 440-450° C., and the medium-temperature stabilization treatment time is 2 hours.

[0007] Furthermore, the surface pre-oxidation treatment includes: The heat-treated green block was placed in an argon atmosphere with an oxygen content of 5-10%, heated at 600°C for 1 hour, and then naturally cooled.

[0008] Furthermore, the spark plasma sintering temperature is 750-850°C, the sintering time is 5-10 min, the pressure during the sintering process is 30-50 MPa, and the vacuum degree is ≤10 -3 Pa.

[0009] Furthermore, the ball-to-material ratio in the high-energy ball mill is 10:1, the rotation speed in the high-energy ball mill during the ball milling process is 300 rpm, and the ball milling time is 19-21 hours; After ball milling in a high-energy ball mill, the composite powder was passed through a 100-mesh sieve to obtain a uniformly mixed composite powder.

[0010] Furthermore, the vacuum drying process is carried out at a drying temperature of 100-150° C. and a drying time of 2-3 hours.

[0011] Further, the method includes providing ingredients, wherein the ingredients include the following raw materials in parts by weight: 78-84 parts copper, 12-15 parts nickel, 4-6 parts tin, 0.5-2 parts gallium and / or indium.

[0012] Further, the method includes providing ingredients, wherein the ingredients include the following raw materials in parts by weight: 79-82 parts copper, 13-14 parts nickel, 4-6 parts tin, 0.5-1.5 parts gallium and / or indium.

[0013] Furthermore, the present invention also provides a copper-nickel-tin alloy capable of improving oxidation resistance, which is a copper-nickel-tin alloy prepared according to the above preparation method.

[0014] Furthermore, the present invention also provides an application of a copper-nickel-tin alloy capable of improving oxidation resistance, and the application of the copper-nickel-tin alloy prepared according to the above preparation method in the fields of electronic components, automobile manufacturing, and aerospace materials.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention uses powder metallurgy to uniformly disperse and add low-melting-point metal gallium and / or indium. This allows the low-melting-point metal to liquefy at high temperatures and migrate to oxidation cracks, filling defects and forming new oxide films. This achieves the purpose of introducing a liquid-phase self-repair mechanism and extending the antioxidant life. 2. The copper-nickel-tin alloy prepared by the present invention is triggered autonomously during the repair process without external intervention. The addition amount of gallium and / or indium is low, and the electrical and thermal conductivity of the substrate is less affected. DETAILED DESCRIPTION

[0016] The technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0017] The present invention provides a technical solution: a method for preparing a copper-nickel-tin alloy capable of improving oxidation resistance, comprising the following steps: High-purity copper powder, nickel powder, tin powder and gallium powder and / or indium powder are vacuum dried respectively, then placed in a high-energy ball milling tank, ball milled under argon protection, and then sieved to obtain a uniformly mixed composite powder; The composite powder is placed in a graphite mold, pre-pressed by a cold isostatic press, and densified by spark plasma sintering to obtain a green block; The green block is placed in a vacuum furnace for heat treatment and then subjected to surface pre-oxidation treatment.

[0018] It should be noted that high-purity copper, nickel, and tin powders (e.g., particle size ≤50μm) are selected as the matrix material, and low-melting-point metal powders gallium and / or indium are added, with a melting point <30°C and a purity ≥99.9%. The powders are vacuum dried to remove surface adsorbed water; gallium and / or indium can be liquefied at high temperatures (within the alloy's operating temperature range) and migrate to the oxidation cracks by capillary action.

[0019] Copper, nickel, tin and gallium and / or indium powders are loaded into a high-energy ball mill and ball milled under argon protection. A uniformly mixed composite powder is obtained by screening. During the ball milling process, plastic deformation and cold welding refine the powder particles and increase the interface bonding area. The argon environment prevents the gallium and / or indium from oxidizing and failing during the ball milling process.

[0020] High-energy ball milling is used to achieve nano-scale mixing of the raw materials to avoid agglomeration of gallium and / or indium. Heat treatment is used to induce gallium and / or indium to segregate to grain boundaries, forming a uniform "storage network" to ensure that when oxidation cracks appear, liquid gallium and / or indium can quickly migrate to the damaged area through the grain boundaries, avoiding the occurrence of repair failure due to local depletion of gallium and / or indium due to uneven distribution, or the occurrence of intergranular corrosion due to enrichment of gallium and / or indium.

[0021] In a further embodiment of this embodiment, the heat treatment includes low-temperature aging heat treatment and medium-temperature stabilization heat treatment: During the low-temperature aging heat treatment, the temperature in the vacuum furnace is adjusted to 240-260°C, and the low-temperature aging treatment time is 2-8 hours; During the medium-temperature stabilization heat treatment, the temperature in the vacuum furnace is adjusted to 440-450° C., and the medium-temperature stabilization treatment time is 2 hours.

[0022] It should be noted that the sintered blank is subjected to a two-stage heat treatment in a vacuum furnace: low-temperature aging: 240-260°C×2-8h, to promote the segregation of gallium and / or indium elements to the grain boundaries; medium-temperature stabilization: 440-450°C×2h, to induce the copper-nickel-tin matrix to form a uniform solid solution; low-temperature aging makes gallium and / or indium enriched at the grain boundaries, providing a "storage pool" for subsequent oxidation crack repair; medium-temperature treatment eliminates internal stress and avoids large-scale diffusion loss of gallium and / or indium.

[0023] In a further embodiment of this embodiment, the surface pre-oxidation treatment includes: The heat-treated green block is placed in an argon atmosphere with an oxygen content of 5-10%, heated at 600°C for 1 hour, and then naturally cooled to achieve the purpose of forming a pre-oxidation film. As an initial protective layer, it delays further oxidation in subsequent service. The microcracks in the pre-oxidation film can serve as preferential channels for the liquid phase migration of gallium and / or indium. The low oxygen partial pressure can avoid the large-scale consumption of gallium and / or indium during the pre-oxidation stage.

[0024] In a further embodiment of this embodiment, the spark plasma sintering temperature is 750-850°C, the sintering time is 5-10 min, the pressure during the sintering process is 30-50 MPa, and the vacuum degree is ≤10 -3 Pa, densification is carried out by spark plasma sintering. The pulse current of spark plasma sintering generates local Joule heat, shortens the sintering time, and avoids premature volatilization of gallium and / or indium. Too low temperature will lead to insufficient powder diffusion and increased porosity, while too high temperature will lead to tin segregation or local liquid phase formation.

[0025] In a further embodiment of this embodiment, the ball-to-material ratio in the high-energy ball mill is 10:1, the rotation speed in the high-energy ball mill during the ball milling process is 300 rpm, and the ball milling time is 19-21 h; After ball milling in a high-energy ball mill, the composite powder was passed through a 100-mesh sieve to obtain a uniformly mixed composite powder.

[0026] In a further embodiment of this example, the vacuum drying is carried out at a drying temperature of 100-150° C. and a drying time of 2-3 h.

[0027] In a further embodiment of this embodiment, ingredients are provided, and the ingredients include the following raw materials in parts by weight: 78-84 parts copper, 12-15 parts nickel, 4-6 parts tin, 0.5-2 parts gallium and / or indium.

[0028] In a further embodiment of this embodiment, ingredients are provided, and the ingredients include the following raw materials in parts by weight: 79-82 parts copper, 13-14 parts nickel, 4-6 parts tin, 0.5-1.5 parts gallium and / or indium.

[0029] It should be noted that: copper in each raw material ensures the electrical / thermal conductivity of the alloy, nickel improves high-temperature strength and oxidation resistance, promotes the formation of a nickel oxide protective layer, tin enhances corrosion resistance, and cooperates with nickel to form a dense tin oxide film, gallium and / or indium ensure the continuity of the repair liquid phase. Too low a content will lead to a repair blind spot, and too high a content will lead to a decrease in the mechanical properties of the matrix.

[0030] Furthermore, the present invention also provides a copper-nickel-tin alloy capable of improving oxidation resistance. The copper-nickel-tin alloy prepared according to the above preparation method can reduce the high-temperature oxidation rate by more than 55%, the self-repair response time is less than 1 minute, and the oxide film life is extended by 3-5 times.

[0031] Example 1

[0032] Weigh the raw materials: 78 parts copper powder, 12 parts nickel powder, 4 parts tin powder and 0.5 parts gallium powder; High-purity copper powder, nickel powder, tin powder and gallium powder were vacuum dried at 150°C for 2 hours to remove surface adsorbed water, and then loaded into a high-energy ball mill under argon protection with a ball-to-material ratio of 10:1. The speed of the high-energy ball mill was 300 rpm for 19 hours. After ball milling, a uniform composite powder was obtained by passing through a 100-mesh sieve.

[0033] The composite powder was loaded into a graphite mold and pre-pressed in a cold isostatic press at a pressure of 200 MPa for 5 min. Then, the composite powder was sintered by spark plasma sintering (SPS) at a temperature of 750 ° C, a sintering time of 5 min, a pressure of 50 MPa, and a vacuum degree of ≤10 -3 Pa is densified and sintered to obtain a green block.

[0034] The green block was placed in a vacuum furnace and first subjected to low-temperature aging treatment at 240°C for 2 hours, and then subjected to medium-temperature stabilization treatment at 440°C for 2 hours to form a uniform solid solution.

[0035] The solid solution is placed in an argon atmosphere with an oxygen content of 5% and heated to 600°C for pre-oxidation for 1 hour, and then naturally cooled to room temperature to form a NiO-SnO2 mixed oxide film with a thickness of 1-2 μm on the surface, thereby obtaining a copper-nickel-tin alloy with improved oxidation resistance.

[0036] Example 2

[0037] The difference from Example 1 is that the raw materials are weighed: 79 parts of copper powder, 15 parts of nickel powder, 5 parts of tin powder and 1 part of gallium powder.

[0038] Example 3

[0039] The difference from Example 1 is that the raw materials are weighed: 80.5 parts of copper powder, 12 parts of nickel powder, 6 parts of tin powder and 1.5 parts of indium powder.

[0040] Example 4

[0041] The difference from Example 1 is that the raw materials are weighed: 84 parts of copper powder, 15 parts of nickel powder, 6 parts of tin powder and 2 parts of indium powder.

[0042] Example 5

[0043] The difference from Example 2 is that the ball milling time is 20 h.

[0044] Example 6

[0045] The difference from Example 2 is that the ball milling time is 21 h.

[0046] Example 7

[0047] The difference from Example 5 is that the spark plasma sintering temperature is 800°C.

[0048] Example 8

[0049] The difference from Example 2 is that the spark plasma sintering temperature is 850°C.

[0050] Example 9

[0051] The difference from Example 7 is that the solid solution is placed in an argon atmosphere with an oxygen content of 8% and heated to 600° C. for pre-oxidation for 1 hour.

[0052] Example 10

[0053] The difference from Example 7 is that the solid solution is placed in an argon atmosphere with an oxygen content of 10% and heated to 600° C. for pre-oxidation for 1 hour.

[0054] Comparative Example 1 The difference from Example 3 is that the raw materials are weighed: 80.5 parts of copper powder, 12 parts of nickel powder, and 6 parts of tin powder.

[0055] Comparative Example 2 The difference from Example 2 is that the ball milling time is 15 h.

[0056] Comparative Example 3 The difference from Example 2 is that the ball milling time is 25 h.

[0057] Comparative Example 4 The difference from Example 5 is that the spark plasma sintering temperature is 700°C.

[0058] Comparative Example 5 The difference from Example 5 is that the spark plasma sintering temperature is 900°C.

[0059] Comparative Example 6 The difference from Example 7 is that the solid solution is placed in an argon atmosphere with an oxygen content of 12% and heated to 600° C. for pre-oxidation for 1 hour.

[0060] Atomic probe tomography grain boundary segregation analysis was performed on the copper-nickel-tin alloys prepared in Examples 1 to 9 and Comparative Examples 2 to 6, respectively. A focused ion beam (FIB) was used to prepare needle-shaped samples with a tip curvature radius of <50 nm. A pulse voltage was applied at a pulse frequency of 200 kHz and a temperature of 50 K. Atoms were peeled off layer by layer and detected, and the three-dimensional atomic distribution was reconstructed. The concentration of gallium and / or indium at the grain boundaries was counted to obtain the continuous network coverage, as shown in Tables 1 to 4 below.

[0061] The copper-nickel-tin alloys prepared in Examples 1 to 9 and Comparative Examples 2 to 6 were subjected to high-temperature tensile tests. The samples were heated to 600°C in a high-temperature furnace and kept warm for 30 minutes. The samples were subjected to high-temperature tensile tests at the same strain rate of 1×10 -3 s -1 The high temperature yield strength obtained by stretching is shown in Tables 1 to 4 below.

[0062] The copper-nickel-tin alloys prepared in Examples 1 to 9 and Comparative Examples 1 to 6 were oxidized at 800° C. for 100 h, and the weight gains of the alloys were statistically analyzed and shown in Tables 1 to 4 below.

[0063] Table 1

[0064] As shown in Table 1, the copper-nickel-tin alloys prepared by Examples 1-4 have low weight gains after oxidation under high temperature conditions. Adding gallium and / or indium to the alloy can effectively increase the high-temperature oxidation resistance of the copper-nickel-tin alloy, among which Examples 2 and 3 have better high-temperature oxidation resistance. However, the high mass proportion of gallium and / or indium added in Example 4 will lead to a decrease in the mechanical properties of the alloy matrix.

[0065] Table 2

[0066] As shown in Table 2, a ball milling time of 19-20 h can effectively achieve uniform distribution of gallium and / or indium, while a ball milling time that is too low will result in uneven powder mixing, and gallium and / or indium will easily agglomerate to form micron-sized particles. On the other hand, a ball milling time that is too long will cause excessive cold welding and powder agglomeration, which will lead to a decrease in uniformity, thereby resulting in a decrease in the continuous network coverage of gallium and / or indium, resulting in a decrease in the high-temperature oxidation resistance of the alloy. As shown in Example 5, a ball milling time of 20 h is the best embodiment, which has the highest distribution uniformity and the best high-temperature oxidation resistance.

[0067] Table 3

[0068] As shown in Table 3, spark plasma sintering temperatures in the range of 750-850°C can effectively achieve rapid sintering through plastic flow. Short-term sintering reduces the volatilization loss of gallium and / or indium, thereby increasing the continuous network coverage of gallium and / or indium, and further increasing the high-temperature oxidation resistance of the alloy. However, if the sintering temperature is too low, insufficient diffusion of the powder will result, the porosity of the alloy will increase, and the coverage will decrease, affecting the oxidation resistance. On the other hand, if the sintering temperature is too high, tin segregation or the formation of a local liquid phase will occur, which will also lead to a decrease in oxidation resistance. As shown in Example 7, the alloy produced by spark plasma sintering at a temperature of 800°C has the best high-temperature oxidation resistance.

[0069] Table 4

[0070] As shown in Table 4, pre-oxidation of the solid solution at 600°C for 1 hour in an argon atmosphere with an oxygen content of 5-10% can prevent the large-scale consumption of gallium and / or indium during the pre-oxidation stage. During the pre-oxidation process, a 1-2 μm thick NiO-SnO2 mixed oxide film is generated. This serves as an initial protective layer. The microcracks in the pre-oxidation film provide a preferential channel for the subsequent migration of gallium and / or indium, accelerating dynamic repair. However, excessive oxygen content will cause a large amount of gallium and / or indium to be consumed during the pre-oxidation stage, thereby reducing the alloy's resistance to high-temperature oxidation.

[0071] In summary, by uniformly dispersing and adding low-melting-point metal gallium and / or indium through powder metallurgy, the low-melting-point metal can be liquefied at high temperature and migrate to the oxidation cracks, filling the defects and forming a new oxide film, thereby introducing a liquid phase self-repair mechanism and extending the antioxidant life. The copper-nickel-tin alloy is triggered autonomously during the repair process without the need for external intervention. The addition amount of gallium and / or indium is low, and has little effect on the electrical and thermal conductivity of the substrate.

[0072] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

Claims

1. A method for preparing a copper-nickel-tin alloy capable of improving oxidation resistance, characterized in that: The following steps are involved: High-purity copper powder, nickel powder, tin powder and gallium powder and / or indium powder are vacuum dried respectively, then placed in a high-energy ball milling tank, ball milled under argon protection, and then sieved to obtain a uniformly mixed composite powder; The composite powder is placed in a graphite mold, pre-pressed by a cold isostatic press, and densified by spark plasma sintering to obtain a green block; The green block is placed in a vacuum furnace for heat treatment and then subjected to surface pre-oxidation treatment.

2. The method for preparing a copper-nickel-tin alloy capable of improving oxidation resistance according to claim 1, wherein: The heat treatment includes low temperature aging heat treatment and medium temperature stabilization heat treatment: During the low-temperature aging heat treatment, the temperature in the vacuum furnace is adjusted to 240-260°C, and the low-temperature aging treatment time is 2-8 hours; During the medium-temperature stabilization heat treatment, the temperature in the vacuum furnace is adjusted to 440-450° C., and the medium-temperature stabilization treatment time is 2 hours.

3. The method for preparing a copper-nickel-tin alloy capable of improving oxidation resistance according to claim 1, wherein: The surface pre-oxidation treatment comprises: The heat-treated green block was placed in an argon atmosphere with an oxygen content of 5-10%, heated at 600°C for 1 hour, and then naturally cooled.

4. The method for preparing a copper-nickel-tin alloy capable of improving oxidation resistance according to claim 1, wherein: The spark plasma sintering sintering temperature is 750-850°C, the sintering time is 5-10min, the pressure during the sintering process is 30-50MPa, and the vacuum degree is ≤10 -3 Pa.

5. The method for preparing a copper-nickel-tin alloy capable of improving oxidation resistance according to claim 1, wherein: The ball-to-material ratio in the high-energy ball mill is 10:1, the rotation speed in the high-energy ball mill during the ball milling process is 300 rpm, and the ball milling time is 19-21 hours; After ball milling in a high-energy ball mill, the composite powder was passed through a 100-mesh sieve to obtain a uniformly mixed composite powder.

6. The method for preparing a copper-nickel-tin alloy capable of improving oxidation resistance according to claim 1, wherein: The vacuum drying process has a drying temperature of 100-150° C. and a drying time of 2-3 hours.

7. The method for preparing a copper-nickel-tin alloy capable of improving oxidation resistance according to claim 1, wherein: The method comprises providing ingredients, wherein the ingredients include the following raw materials in parts by weight: 78-84 parts copper, 12-15 parts nickel, 4-6 parts tin, 0.5-2 parts gallium and / or indium.

8. The method for preparing a copper-nickel-tin alloy capable of improving oxidation resistance according to claim 7, wherein: The method comprises providing ingredients, wherein the ingredients include the following raw materials in parts by weight: 79-82 parts copper, 13-14 parts nickel, 4-6 parts tin, 0.5-1.5 parts gallium and / or indium.

9. A copper-nickel-tin alloy capable of improving oxidation resistance, characterized in that: A copper-nickel-tin alloy prepared according to the preparation method according to any one of claims 1 to 8.

10. An application of a copper-nickel-tin alloy capable of improving oxidation resistance, characterized in that: Application of the copper-nickel-tin alloy prepared according to the preparation method according to any one of claims 1 to 8 in the fields of electronic components, automobile manufacturing and aerospace materials.

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