High-temperature alloy filler metal and high-temperature alloy welded part

Abstract

The application discloses a brazing filler metal and a high-temperature alloy welded piece. The brazing filler metal comprises a parent brazing filler metal alloy and a binder; the parent brazing filler metal alloy comprises the following components: Cr, 15-21%; Co, 7.5-13%; Fe, 2-11%; Ta, 3.5-7%; Al, 1.5-5.5%; Mo, 1-6%; B, 1.2-3.2%; Y, 0.01-0.12%; and Ni, the balance; the percentages are mass percentages of the components in the parent brazing filler metal alloy. The brazing filler metal can reduce brittle eutectic phases such as borides in the weld, thereby improving the mechanical properties of the weld and the remelting temperature; the brazing temperature and time of the brazing filler metal are consistent with the heat treatment process of the laser selective melting formed alloy, and the brazing is simultaneously performed during the heat treatment; further, the brazing joint formed by the brazing filler metal is not prone to remelting during subsequent hot isostatic pressing.

Description

Technical Field

[0001] This invention belongs to the field of welding, specifically relating to a high-temperature alloy brazing filler metal and a high-temperature alloy welded component. Background Technology

[0002] Metal additive manufacturing technology enables the moldless, rapid, and fully dense near-net-shape forming of high-performance, complex metal parts, making it the best new technology for addressing the technological challenges in the aero-engine field. Selective laser melting (SLM), a typical metal additive manufacturing technology, is gradually being applied to complex, high-precision high-temperature alloy components such as fuel nozzles and pre-swirl nozzles for aero-engines. However, SLM currently struggles to achieve the one-piece forming of complex components with extremely high precision requirements; local precision machining of the additively manufactured parts is still necessary before welding is used for assembly. Taking additively manufactured fuel nozzle assemblies as an example, currently, Hastelloy X alloy powder is mainly used to prepare parts using SLM, which are then joined into assemblies using vacuum brazing.

[0003] However, the composition control of laser selective melting (SLM) alloys differs significantly from that of cast-forged alloys of the same grade. Therefore, SLM superalloys and cast-forged superalloys differ in composition, grain structure, and precipitated phases. This difference alters the interaction between the filler metal and the base material during vacuum brazing, leading to changes in the weld microstructure. Since general filler metals are not designed for SLM alloys, their processability is poor, and the brazed weld is prone to developing large amounts of boride eutectic phases. These eutectic compounds may reduce the weld's mechanical properties and remelting temperature. Furthermore, the brazing temperature of commercial filler metals often differs from the heat treatment temperature of SLM superalloys. SLM superalloy parts require brazing after heat treatment, and the brazing process may adversely affect the microstructure and properties of the SLM superalloy. Summary of the Invention

[0004] The purpose of this invention is to provide a high-temperature alloy brazing filler metal that improves the performance of the brazing microstructure of laser selective melting alloys. This invention also provides a high-temperature alloy welded component.

[0005] According to one aspect of the present invention, a high-temperature alloy solder is provided, the high-temperature alloy solder comprising a solder alloy, wherein the solder alloy comprises, by weight: Cr: 15%–21%, Co: 7.5%–13%, Fe: 2%–11%, Ta: 3.5%–7%, Al: 1.5%–5.5%, Mo: 1%–6%, B: 1.2%–3.2%, Y: 0.01%–0.12%, Ni: balance, and unavoidable impurities.

[0006] Cr is mainly dissolved in the Ni matrix, improving joint strength and high-temperature oxidation resistance; Co is dissolved in the Ni matrix, increasing the joint's service temperature and strength; Fe improves the solder's fluidity and joint toughness; Ta increases the joint's service temperature and strength; Al refines the joint grains and improves oxidation resistance; Mo improves joint strength and resistance to plastic deformation; Bo mainly lowers the solder's melting point and improves wettability; Y refines the grains, improves solder fluidity, and enhances joint toughness. Compared to commercial solders like AMS4777, this solder has increased the content of solid-solution elements such as Cr and Co, improving weld strength and oxidation resistance; the addition of alloying elements such as Ta and Al helps improve weld service temperature and strength; and the reduced content of demelting elements such as Si and B decreases the formation of brittle compounds and increases the weld remelting temperature.

[0007] Furthermore, the brazing alloy is configured as an alloy strip or alloy powder; when the brazing alloy is configured as an alloy powder, the high-temperature alloy brazing alloy further includes a binder, the binder including one or more of polymethyl methacrylate, trichloroethylene, polystyrene, trichloroethylene and water-based binders.

[0008] Further, the solder alloy comprises, by weight: Cr: 15.5%–20.5%, Co: 10%–12.5%, Fe: 2.2%–10.7%, Ta: 5%–6.9%, Al: 1.6%–3.5%, Mo:

[0009] 1.5%–5%, B: 1.5%–2.5%, Y: 0.03%–0.10%, with the balance being Ni and unavoidable impurities. Further optimization of the brazing alloy composition can improve brazing performance.

[0010] Furthermore, the brazing alloy is configured as an alloy powder, wherein the mass ratio of the alloy powder to the binder is 15:1 to 10:1.

[0011] Furthermore, the brazing alloy is configured as alloy powder, which is produced by gas atomization of alloy ingots smelted according to the brazing alloy composition.

[0012] According to another aspect of the present invention, a high-temperature alloy weldment is provided, comprising a base material and a weld structure, wherein the base material is formed by laser selective melting of an alloy, and the weld structure is formed by brazing the base material with the high-temperature alloy brazing filler metal described in any of the foregoing embodiments.

[0013] Furthermore, the base material is Hastelloy X alloy, GH625 alloy, or GH4169 alloy, and welding is simultaneously performed during the heat treatment after laser selective melting forming of the base alloy. Using this brazing filler metal, vacuum brazing can be performed simultaneously with heat treatment of laser selective melting forming of Hastelloy X alloy, GH625 alloy, or GH4169 alloy. Weld inspection shows that the weld quality is good, brittle compounds are significantly reduced, and the high-temperature tensile strength and creep time of the joint exceed the performance indicators of the base material.

[0014] Furthermore, the high-temperature alloy welded parts are manufactured by vacuum brazing.

[0015] Furthermore, the welding parameters for the vacuum brazing are: heating temperature 1100℃-1200℃, and pressure not exceeding 4×10⁻⁶. -2 Pa, heat preservation time 0.5-2h, cooling termination temperature not higher than 80℃.

[0016] Furthermore, the high-temperature tensile strength and creep time of the welded structure are not lower than those of the base material, and no remelting occurs in the welded structure after hot isostatic pressing at 1100℃-1200℃ for at least 2 hours with a pressure of not less than 160MPa. Attached Figure Description

[0017] Figure 1 This is a scanning electron microscope image of a powdered brazing alloy in one embodiment;

[0018] Figure 2 Here is a metallographic photograph of the weld structure in one embodiment;

[0019] Figure 3 Metallographic photograph of the weld structure in another embodiment;

[0020] Figure 4 Here is a metallographic photograph of the weld structure in another embodiment;

[0021] Figure 5 A pair of proportional scanning electron microscope images of weld microstructure;

[0022] Figure 6 Here are scanning electron microscope images of the weld microstructure in another pair of proportions. Detailed Implementation

[0023] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0024] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment herein. The phrase appearing in various places in the specification does not necessarily refer to the same embodiment, nor is it limited to mutually exclusive, independent, or alternative embodiments. Those skilled in the art will understand that the embodiments herein can be combined with other embodiments without causing structural conflicts.

[0025] The deposited alloys prepared by selective laser-area melting (SLM) technology are mainly composed of arched molten pools with anisotropic grain structure, while traditional cast-forged superalloys are mainly composed of isotropic equiaxed grains. Furthermore, to avoid defects such as cracks in SLM alloys, strict control is exercised over solid solution elements such as Cr and trace elements such as C and Si. The composition control of SLM alloys differs significantly from that of cast-forged alloys of the same grade. Therefore, SLM superalloys and cast-forged superalloys differ in composition, grain structure, and precipitates. This difference alters the interaction between the brazing filler metal and the base metal during vacuum brazing, leading to changes in the weld microstructure. Currently, traditional commercial brazing filler metals such as BNi-2 (AMS4777) and BCo-1 (AMS4783) are mainly used for brazing cast-forged Hastelloy X alloys. Because this type of solder is not designed for laser selective melting forming of Hastelloy X alloys, its processability is poor. In a comparative example, the weld microstructure of laser selectively formed Hastelloy X alloys soldered using BNi-2 (AMS4777) solder is as follows: Figure 5 As shown, in another comparative example, the weld microstructure of Hastelloy X alloy soldered using BCo-1 (AMS4783) brazing filler metal is as follows: Figure 6 As shown, a large number of boride eutectic phases appear in the microstructure of the brazed weld. These eutectic compounds may reduce the mechanical properties and remelting temperature of the weld. Furthermore, the brazing temperature of commercial brazing filler metals often differs from the heat treatment temperature of the alloy. Laser selective melting (LSM) high-temperature alloy parts require brazing after heat treatment, and the brazing process may adversely affect the microstructure and properties of the high-temperature alloy. For example, LSM Hastelloy X alloy typically requires heat treatment at 1175℃ for 1 hour, followed by vacuum brazing at 1020–1100℃ using AMS4777 filler metal. To improve the density of LSM parts, some parts require further brazing after heat treatment at 1175℃.

[0026] Hot isostatic pressing (160 MPa) for 2 hours at ℃. However, during subsequent heat treatment, the weld structure using conventional commercial brazing filler metal may experience localized remelting, leading to further degradation of the finished weldment's properties, particularly its high-temperature mechanical properties and creep rupture properties.

[0027] To address the aforementioned problems, one embodiment of the present invention provides a high-temperature alloy brazing filler metal, wherein, by weight, the filler metal alloy comprises Cr: 15%–21%, Co:

[0028] 7.5%–13%, Fe: 2%–11%, Ta: 3.5%–7%, Al: 1.5%–5.5%, Mo: 1%–6%, B: 1.2%–3.2%, Y: 0.01%–0.12%, Ni: balance, and unavoidable impurities; in a preferred embodiment, the solder alloy, by weight, comprises Cr: 15.5%–20.5%, Co: 10%–12.5%, Fe: 2.2%–10.7%, Ta: 5%–6.9%, Al: 1.6%–3.5%, Mo:

[0029] 1.5%–5%, B: 1.5%–2.5%, Y: 0.03%–0.10%, balance being Ni and unavoidable impurities.

[0030] The superior joint performance of this high-temperature alloy brazing filler metal is due to the following: Cr is mainly dissolved in the Ni matrix, improving joint strength and high-temperature oxidation resistance; Co is dissolved in the Ni matrix, increasing the joint's operating temperature and strength; Fe improves the filler metal's fluidity and joint toughness; Ta increases the joint's operating temperature and strength; Al refines the joint grains and improves oxidation resistance; Mo improves joint strength and resistance to plastic deformation; Bo mainly lowers the filler metal's melting point and improves wettability; Y refines the grains, improves filler metal fluidity, and enhances joint toughness. Compared to commercial brazing filler metals such as AMS4777, the increased content of dissolved elements like Cr and Co improves weld strength and oxidation resistance; the addition of alloying elements like Ta and Al helps improve weld operating temperature and strength; and the reduced content of demelting elements like Si and B decreases the formation of brittle compounds and increases weld remelting temperature.

[0031] Depending on the application scenario, the solder can be in the form of rolled alloy strips or prepared as a powder mixed with a binder to form a paste. In some embodiments, the solder alloy powder is mixed with one or more supporting binders selected from polymethyl methacrylate, trichloroethylene, polystyrene, trichloroethylene, and water-based binders to form a paste-like solder. In a preferred embodiment, the mass ratio of solder alloy powder to binder is 15:1 to 10:1. In some embodiments, the solder alloy powder is prepared by gas atomization treatment of an alloy ingot prepared by vacuum melting according to the solder alloy proportions, and the powder morphology of the solder alloy powder is as follows. Figure 1 As shown; in other embodiments, it can also be prepared by processes such as ball milling or ion sputtering.

[0032] In another embodiment of the present invention, a high-temperature alloy welded component is provided.

[0033] In one embodiment, brazing of a Hastelloy X alloy base material formed by high laser selective melting involves the following steps:

[0034] First, the solder is prepared. The elemental composition by weight percentage includes: Cr 15.9%, Co 10.5%, Fe 2.7%, Ta 3.5%, Al 2.9%, Mo 1.5%, B 2.1%, Y 0.03%, with the balance being Ni. The master alloy ingot for the solder is melted in a vacuum induction furnace, and then atomized into alloy powder (its morphology is shown in the figure). Figure 3 (as shown), and add binder to make a paste-like solder.

[0035] Next, the surface of the Hastelloy X sample to be welded was polished and cleaned with alcohol to remove dirt and grease, and the cleanliness of the surface was confirmed to meet the requirements. A paste-like brazing filler metal was applied to the area to be welded, and the sample was assembled. The assembled weldment was then placed in a furnace for vacuum brazing. Heating was initiated under a furnace pressure below 4 × 10⁻² Pa, and the temperature was increased to the alloy's heat treatment temperature of 1175°C, held for 1 hour, and then cooled to below 80°C before being removed from the furnace. Simultaneously with vacuum brazing, the Hastelloy X alloy underwent laser selective melting and forming heat treatment.

[0036] Visual and metallographic analysis were performed on the brazed specimens, and the weld microstructure was as follows: Figure 2 As shown, weld microstructure 1 is well-developed, with no cracks or boride precipitation, and no obvious brittle inclusions, achieving a good bond with the base material 2. Tensile tests were conducted at room temperature and high temperature using a Tinius-Olsen tensile testing machine according to ASTM E8M and ASTM E21 standards, respectively. The room temperature tensile strength and the tensile strength at 815℃ were 615 MPa and 306 MPa, respectively, with the sample fracture within the range of weld microstructure 1. During creep rupture testing at 815℃ / 105 MPa using an RDL50 high-temperature creep testing machine according to ASTM E139 standard, the creep time was 35 hours, and the sample fractured within the range of weld microstructure 1.

[0037] No remelting structure was found in the brazed joint during hot isostatic pressing at (1175℃, 160MPa)×2h.

[0038] In another embodiment, the Hastelloy X alloy base material formed by high laser selective melting is brazed, and the steps are as follows:

[0039] First, the solder is prepared. The elemental composition by weight percentage includes: Cr 20.5%, Co 12.5%, Fe 10.7%, Ta 5.1%, Al 1.6%, Mo 3.5%, B 1.5%, Y 0.12%, with the balance being Ni. The master alloy ingot of the solder is melted in a vacuum induction furnace, and then the master alloy ingot is prepared into alloy powder by gas atomization. A binder is added to form a paste-like solder.

[0040] Next, the surface of the Hastelloy X sample to be welded was polished and cleaned with alcohol to remove dirt and grease, and the cleanliness of the surface was confirmed to meet the requirements. A paste-like brazing filler metal was applied to the area to be welded, and the sample was assembled. The assembled weldment was then placed in a furnace for vacuum brazing. Heating was initiated under a furnace pressure below 4 × 10⁻² Pa, and the temperature was increased to the alloy's heat treatment temperature of 1175°C, held for 1 hour, and then cooled to below 80°C before being removed from the furnace. Simultaneously with vacuum brazing, the Hastelloy X alloy underwent laser selective melting and forming heat treatment.

[0041] Visual and metallographic analysis were performed on the brazed specimens, and the weld microstructure was as follows: Figure 3 As shown, weld microstructure 1 is well-developed, with no cracks or boride precipitation, no obvious brittle inclusions, and a small amount of precipitates with a diameter of approximately 10μm-30μm at the grain boundaries. A good bond is formed between weld microstructure 1 and the base material 2. Tensile tests were conducted at room temperature and high temperature using a Tinius-Olsen tensile testing machine according to ASTM E8M and ASTM E21 standards, respectively. The room temperature tensile strength and the tensile strength at 815℃ were 639MPa (fracture location within weld microstructure 1) and 319MPa (fracture location within base material 2), respectively. During creep rupture testing at 815℃ / 105MPa using an RDL50 high-temperature creep testing machine according to ASTM E139 standard, the creep time was 41 hours (fracture location within weld microstructure 1).

[0042] No remelting structure was found in the brazed joint during hot isostatic pressing at (1175℃, 160MPa)×2h.

[0043] In yet another embodiment, the Hastelloy X alloy base material formed by high laser selective melting is brazed, and the steps are as follows:

[0044] First, the solder is prepared. The elemental composition by weight percentage includes: Cr 17.8%, Co 12.1%, Fe 2.2%, Ta 6.9%, Al 3.2%, Mo 1.0%, B 2.0%, Y 0.08%, with the balance being Ni. The master alloy ingot of the solder is melted in a vacuum induction furnace, and then the master alloy ingot is prepared into alloy powder by gas atomization. A binder is added to form a paste-like solder.

[0045] Next, the surface of the Hastelloy X sample to be welded was polished and cleaned with alcohol to remove surface dirt and grease, and the cleanliness of the surface to be welded was confirmed to meet the requirements. A paste-like brazing filler metal was applied to the area to be welded, and the sample was assembled. The assembled welded parts were then placed in a furnace for vacuum brazing. Heating began under a furnace pressure below 4 × 10⁻² Pa, and the temperature was increased to the alloy's heat treatment temperature of 1175℃. The temperature was held for 1 hour to 2 hours, and then cooled to below 80℃ before being removed from the furnace. Simultaneously with vacuum brazing, the Hastelloy X alloy underwent laser selective melting and forming heat treatment.

[0046] Visual and metallographic analysis were performed on the brazed specimens, and the weld microstructure was as follows: Figure 4 As shown, weld microstructure 1 is well-developed, with no cracks or boride precipitation, no obvious brittle inclusions, and a small number of precipitates with a diameter of less than 10 μm at the grain boundaries. Tensile tests were conducted at room temperature and high temperature on a Tinius-Olsen tensile testing machine according to ASTM E8M and ASTM E21 standards, respectively. The room temperature tensile strength and the tensile strength at 815℃ were 618 MPa and 301 MPa, respectively (both fractured within the range of weld microstructure 1). During creep rupture testing at 815℃ / 105 MPa on an RDL50 high-temperature creep testing machine according to ASTM E139 standard, the creep time was 38 hours (fractured within the range of weld microstructure 1).

[0047] Mechanical properties of the solution-treated Hastelloy X base material were tested. Tensile tests were conducted at room temperature and high temperature using a Tinius-Olsen tensile testing machine according to ASTM E8M and ASTM E21 standards, respectively. The room temperature tensile strength and the tensile strength at 815℃ were 762 MPa and 335 MPa, respectively. Creep testing was performed on an RDL50 high-temperature creep testing machine according to ASTM E139 standard at 815℃ / 105 MPa, with a creep time of 37 hours.

[0048] In contrast, such as Figure 5 The microstructure shown is obtained by welding a solution-treated Hastelloy X base material with BNi-2 commercial solder. The room temperature tensile strength is only 239 MPa, approximately 35% of that of base material 2. Significant boride 3 precipitation is observed in the weld microstructure 1. Figure 6The microstructure obtained by welding solution-treated Hastelloy X base material with BCo-1 commercial brazing filler metal shown in the figure has a room temperature tensile strength of 390 MPa, which is only 57% of that of base material 2. Significant boride 3 precipitation is also observed in the welding apparatus 2. It is evident that the high-temperature alloy welded parts prepared using the high-temperature alloy brazing filler metal provided by this invention have significant advantages in mechanical properties. Furthermore, by combining the brazing and laser selective melting heat treatment processes, processing efficiency is effectively improved and process costs are reduced.

[0049] In other embodiments, the brazing filler metal can also be used for brazing GH625 alloy or GH4169 alloy.

[0050] The purpose of the above embodiments is to provide a more detailed description of the present invention in conjunction with the accompanying drawings, so that those skilled in the art can understand the technical concept of the present invention. Within the scope of the claims of the present invention, optimization or equivalent substitution of the components and processes involved, as well as combination of implementation methods in different embodiments without causing a conflict of principles, all fall within the protection scope of the present invention.

Claims

1. A high temperature alloy weldment comprising a base metal and a weld microstructure, characterized in that, The base material is formed by laser selective melting of Hastelloy X alloy, GH625 alloy or GH4169 alloy, and welding is completed simultaneously in the heat treatment after laser selective melting of the base material alloy; the high-temperature alloy welded part is prepared by vacuum brazing; and the welding structure is formed by brazing of the base material and the high-temperature alloy filler. The high-temperature alloy filler comprises a filler alloy, The filler alloy comprises, by weight ratio: Cr: 15% to 21%, Co: 7.5% to 13%, Fe: 2% to 11%, Ta: 3.5% to 7%, Al: 1.5% to 5.5%, Mo: 1% to 6%, B: 1.2% to 3.2%, Y: 0.01% to 0.12%, Ni: balance, and inevitable impurities; The welding parameters of the vacuum brazing are heating temperature 1100-1200℃, pressure not more than 4×10 -2 Pa, holding time 0.5-2h, and cooling end temperature not higher than 80℃.

2. The high temperature alloy weldment of claim 1, wherein, The filler alloy is configured as an alloy strip or an alloy powder; when the filler alloy is configured as an alloy powder, the high-temperature alloy filler further comprises a binder, and the binder comprises one or more of polymethyl methacrylate, trichloroethylene, polystyrene and a water-based binder.

3. The high temperature alloy weldment of claim 1 or 2, wherein, The filler alloy comprises, by weight ratio: Cr: 15.5% to 20.5%, Co: 10% to 12.5%, Fe: 2.2% to 10.7%, Ta: 5% to 6.9%, Al: 1.6% to 3.5%, Mo: 1.5% to 5%, B: 1.5% to 2.5%, Y: 0.03% to 0.10%, balance of Ni and inevitable impurities.

4. The high temperature alloy weldment of claim 2, wherein, The filler alloy is configured as an alloy powder, and the mass ratio of the alloy powder to the binder is 15:1 to 10:

1.

5. The high temperature alloy weldment of claim 2, wherein, The filler alloy is configured as an alloy powder, and the alloy powder is prepared by gas atomization of an alloy ingot smelted according to the components of the filler alloy.

6. The high temperature alloy weldment of claim 1, wherein, The high-temperature tensile strength and the endurance time of the welding structure are not lower than the performance of the base material, and no remelting occurs in the welding structure after hot isostatic pressing of the welding structure at 1100°C to 1200°C for at least 2h under a pressure not lower than 160MPa.

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