Nb-ti-zr-v filler metal for niobium alloy honeycomb brazing, filler metal coating, and method for manufacturing the same

Abstract

The present application relates to the technical field of welding material, in particular to a Nb-Ti-Zr-V brazing filler metal for Nb alloy honeycomb brazing, a brazing filler metal coating and a preparation method thereof. The Nb-Ti-Zr-V brazing filler metal for Nb alloy honeycomb brazing comprises 10-25% of Nb, 42-52.5% of Ti, 9-11.25% of Zr and 9-11.25% of V in terms of mass percentage. The purpose of the Nb-Ti-Zr-V brazing filler metal for Nb alloy honeycomb brazing, the brazing filler metal coating and the preparation method thereof is to solve the problem of poor welding rate when Ti-Zr-V brazing filler metal is used for honeycomb brazing.

Description

Technical Field

[0001] This invention relates to the field of welding materials technology, specifically to a Nb-Ti-Zr-V brazing filler metal for niobium alloy honeycomb brazing, a brazing filler metal coating, and a method for preparing the same. Background Technology

[0002] As the Mach number of hypersonic vehicles increases, the temperature at the nose tip and wing leading edge reaches 1400℃~1500℃, and the local temperature of the fuselage can reach 1200℃. Currently, the outermost metal honeycomb sandwich structure of the main metal thermal protection system mainly uses high-temperature alloy materials and oxide dispersion reinforced ODS alloys (PM1000, PM2000) and other high-temperature resistant metal materials. However, these materials are difficult to operate at temperatures above 1200℃ and cannot meet the requirements of high Mach number vehicles. Therefore, there is an urgent need to develop refractory high-temperature metal brazed thermal protection honeycomb structures.

[0003] Compared to high-temperature alloys and oxide dispersion strengthened ODS steel, niobium and niobium alloys have excellent properties such as low density, high melting point, high high-temperature specific strength, and good formability. As a refractory metal material, it has high strength in the range of 1150℃ to 1650℃. The development and use of niobium alloy honeycomb can further and effectively improve the service temperature and high-temperature load-bearing capacity of honeycomb sandwich structures.

[0004] Literature review revealed no relevant reports from domestic scholars regarding the brazing process of niobium alloy honeycomb structures; only the United States and Russia conducted related basic research in the last century. American scholars used Pd, Pd-30Cu, Ti, and Ti-11Cr-13V-3Al alloys to study the brazing process of planar and curved niobium alloy honeycomb structures. Pd and Pd-30Cu brazing filler metals showed good filler capacity, full brazing bevels, and good joint toughness; however, the presence of Pd easily led to intergranular infiltration, and the brazing temperature was high, exceeding 1800℃. Pure Ti, due to its good viscosity in the liquid state, is suitable for small-gap brazing, but its high melting point results in brazing temperatures exceeding 1750℃. Compared to pure Ti brazing filler metal, Ti-11Cr-13V-3Al brazing filler metal has a lower melting point, achieving niobium alloy honeycomb brazing at 1620℃. The brazed niobium alloy honeycomb panels can be used at temperatures up to 1316℃, exhibiting good room temperature and high-temperature mechanical properties. In order to eliminate the brittleness of the base material during brazing, Russian scholars studied the brazing filler metal composition system with a melting point of 1400℃~1500℃ and determined two brazing filler metal systems: Ti-20%~30%Zr-3%~30%V and Ti-15%~30%Cr-5%~15%V.

[0005] Therefore, the inventors provide a Nb-Ti-Zr-V brazing filler metal for niobium alloy honeycomb brazing, a brazing filler metal coating, and a method for preparing the same. Summary of the Invention

[0006] (1) Technical problems to be solved

[0007] This invention provides a Nb-Ti-Zr-V brazing filler metal, a brazing filler metal coating, and a method for preparing the same for niobium alloy honeycomb brazing, which solves the technical problem of poor weld rate during Ti-Zr-V honeycomb brazing.

[0008] (2) Technical solution

[0009] The first aspect of the present invention provides an Nb-Ti-Zr-V brazing filler metal for niobium alloy honeycomb, comprising 10-25% Nb, 42-52.5% Ti, 9-11.25% Zr and 9-11.25% V by mass percentage.

[0010] Furthermore, the mass percentages of Nb, Ti, Zr, and V are 25%, 52.5%, 11.25%, and 11.25%, respectively.

[0011] A second aspect of the present invention provides an Nb-Ti-Zr-V brazing filler metal coating for niobium alloy honeycomb brazing, comprising the above-mentioned Nb-Ti-Zr-V brazing filler metal for niobium alloy honeycomb brazing.

[0012] Furthermore, the coating thickness is 40–50 μm.

[0013] A third aspect of the present invention provides a method for preparing an Nb-Ti-Zr-V brazing filler metal coating for niobium alloy honeycomb brazing, comprising the following steps:

[0014] Weigh out the corresponding masses of Nb, Ti, Zr and V elemental powder raw materials according to their mass percentages;

[0015] Each metal element powder is placed in an electric arc melting equipment, vacuumed to the first set value, and then ionized gas is introduced for melting. After cooling in the furnace, a brazing alloy ingot is prepared.

[0016] The solder alloy ingot and the niobium alloy panel are placed in a vapor deposition apparatus, and a vacuum is drawn to a second set value to evaporate the solder alloy ingot and form a solder coating on the surface of the niobium alloy panel.

[0017] Furthermore, the first set value is 10. -3 Pa level.

[0018] Furthermore, the second setting value is 10. -3 Pa level.

[0019] Furthermore, the ionized gas is high-purity Ar.

[0020] (3) Beneficial effects

[0021] In summary, this invention improves the wetting and spreading properties between the brazing filler metal and the honeycomb core by further increasing the Nb element in the Ti-Zr-V brazing filler metal, thereby achieving high-quality welding of Nb521 niobium alloy honeycomb and preventing the production of low-melting-point eutectic phases at the brazing seam interface, thus forming an Nb-Ti-Zr-V brazing filler metal suitable for brazing niobium alloy honeycomb. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1(a) is a secondary electron imaging microstructure of the interface of the brazed sample with 70Ti-15Zr-15V brazing filler metal composition at a brazing temperature of 1600℃.

[0024] Figure 1(b) is a secondary electron imaging microstructure of the interface of the brazed sample with 65Ti-20Zr-15V brazing filler metal composition at a brazing temperature of 1600℃.

[0025] Figure 1(c) shows the secondary electron imaging microstructure of the interface of the brazed sample under the brazing filler metal composition of 60Ti-25Zr-15V at a brazing temperature of 1600℃.

[0026] Figure 1(d) shows the secondary electron imaging microstructure of the interface of the brazed sample with 70Ti-15Cr-15V brazing filler metal composition at a brazing temperature of 1600℃.

[0027] Figure 1(e) shows the secondary electron imaging microstructure of the interface of the brazed sample under the brazing filler metal composition of 65Ti-20Cr-15V at a brazing temperature of 1600℃.

[0028] Figure 1(f) is a secondary electron imaging microstructure of the interface of the brazed sample with 60Ti-25Cr-15V brazing filler metal composition at a brazing temperature of 1600℃.

[0029] Figure 2(a) shows the backscattered microstructure of the interface of the brazed sample with 70Ti-15Zr-15V brazing filler metal composition at a brazing temperature of 1620℃.

[0030] Figure 2(b) shows the backscattered microstructure of the interface of the brazed sample under the brazing filler metal composition of 65Ti-20Zr-15V at a brazing temperature of 1620℃.

[0031] Figure 2(c) shows the backscattered microstructure of the interface of the brazed sample with 60Ti-25Zr-15V brazing filler metal composition at a brazing temperature of 1620℃.

[0032] Figure 3 This is a schematic flowchart of a method for preparing a Nb-Ti-Zr-V brazing filler metal coating for niobium alloy honeycomb brazing, provided in an embodiment of the present invention.

[0033] Figure 4 This is a schematic diagram of a niobium alloy honeycomb sandwich structure brazed with Nb-Ti-Zr-V solder according to an embodiment of the present invention;

[0034] Figure 5(a) is a schematic diagram of the low-magnification metallographic structure of the brazing interface of a niobium alloy honeycomb sandwich layer after brazing with Nb-Ti-Zr-V brazing filler metal according to an embodiment of the present invention.

[0035] Figure 5(b) is a schematic diagram of the high-magnification metallographic structure of the brazing interface of a niobium alloy honeycomb sandwich layer after brazing with Nb-Ti-Zr-V brazing filler metal according to an embodiment of the present invention. Detailed Implementation

[0036] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present invention by way of example, but should not be used to limit the scope of the present invention. That is, the present invention is not limited to the described embodiments, and any modifications, substitutions and improvements to the parts, components and connection methods are covered without departing from the spirit of the present invention.

[0037] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0038] The present invention provides a niobium alloy honeycomb brazing filler metal of Nb-Ti-Zr-V, comprising 10-25% Nb, 42-52.5% Ti, 9-11.25% Zr and 9-11.25% V by mass percentage.

[0039] In the above embodiments, the brazing filler metals used for traditional high-temperature niobium alloy honeycomb brazing are Ti-Zr-V and Ti-Cr-V alloys. These types of brazing filler metals have excessive reactivity with the niobium alloy base material, resulting in a fast melt freezing rate during brazing and poor wetting and spreading performance between the honeycomb core cells.

[0040] Based on the research results of Russian scholars, this invention designs six solder compositions as shown in Table 1.

[0041] Table 1. Niobium alloy brazing filler metal composition design (wt%)

[0042]

[0043]

[0044] The brazing process of niobium alloy was tested using the brazing filler metals shown in Table 1. The process parameters were as follows: the temperature was slowly increased to 1400℃ over 5 hours, held for 30 minutes, then increased again to 1600℃, held for 60 minutes, and then cooled with the furnace. After the brazing test, cross-sectional samples were cut by wire cutting, and metallographic samples were prepared by mounting, polishing, and etching. The microstructure of the brazed sample interface under different filler metal compositions was observed using optical microscopy and scanning electron microscopy. The test results are shown in Figures 1(a) to 1(f).

[0045] As shown in Figures 1(a) to 1(f), for Ti-Zr-V brazing filler metal, the microstructure at the brazing seam interface becomes more complex with the increase of Zr content. Compared with Ti-Zr-V brazing filler metal, Ti-Cr-V brazing filler metal exhibits a more complex microstructure at the brazing seam interface and poorer microstructure uniformity.

[0046] To further investigate the microstructure and composition of the brazed interface, three brazing alloy compositions from the Ti-Zr-V system were selected for further plate-to-plate brazing experiments. This time, the brazing temperature was increased to 1620℃, and the holding time was 1 hour. After the brazing experiment, cross-sectional samples were cut using wire cutting, and metallographic samples were prepared through mounting, polishing, and etching. Analysis was performed using an optical microscope. The resulting microstructure of the brazed interface is shown in the figure. Figures 2(a) to 2(c) As shown.

[0047] As shown in Figure 2(a), the brazing interface of the 70Ti-15Zr-15V brazing filler metal consists of a black blocky structure and a gray matrix. With increasing Zr content, the black blocky structure in the brazing seam increases. When the Zr content in the filler metal increases to 25%, a black layered structure is formed at the brazing seam interface. The elemental composition of the black structure and gray matrix of the three brazing filler metals was tested using the EDS method, as shown in Table 2. The table shows that the main components of the black blocky structure are Ti, Nb, and Zr, while the main elements in the gray matrix are Nb, Ti, V, and W. Based on the binary phase diagram of the elemental relationships, it can be determined that the black blocky structure and the gray matrix are β-(Ti,Zr) and Nb solid solutions, respectively. At high temperatures, Nb has high solubility for Zr, V, and Ti. During cooling, Nb and V are infinitely miscible elements, while the solubility of Ti and Zr decreases. From the binary phase diagrams of Ti-Nb and Zr-Nb, it can be seen that Ti-Nb and Zr-Nb can generate α-Ti and α-Zr at room temperature. Since Ti and Zr are infinitely miscible elements, the reaction β(Nb,Ti,Zr) → β-(Ti,Zr) + Nb of Nb solid solution occurs, thus forming a mixed structure of black blocky Nb solid solution matrix of β-(Ti,Zr) and Nb solid solution.

[0048] Table 2. Elemental composition of different regions at the Ti-Zr-V brazing interface.

[0049]

[0050] Further analysis of the elemental distribution at the brazing interface of the 70Ti-15Zr-15V brazing filler metal revealed that Ti and Zr are enriched in the black blocky structure, with Ti showing a particularly significant enrichment. Nb, Mo, W, and V are enriched in the gray matrix.

[0051] Comparing the experimental results of different compositions in the Ti–Zr–V system, it can be seen that with the increase of Zr element in the solder, the (Ti,Zr) solid solution at the solder joint interface increases. This is mainly because the diffusion coefficient of Zr in Nb is lower than that of Ti. During brazing, the diffusion rate of Zr in the solder is slower, easily forming Zr-rich regions. Subsequently, during the cooling process, when β(Nb,Ti,Zr) transforms into β-(Ti,Zr)+Nb of dissolved Nb, the β-(Ti,Zr) content of dissolved Nb increases, leading to an increase in the black blocky structure. Based on the comprehensive comparison of the experimental results of different compositions in the Ti–Zr–V system, the optimized Nb alloy solder composition is 70Ti-15Zr-15V.

[0052] An experimental study on the brazing process of niobium alloy honeycomb was conducted using an optimized 70Ti-15Zr-15V brazing filler metal. When the Ti-Zr-V brazing filler metal coating thickness was approximately 25 μm, the brazing temperature was 1600℃, and the holding time was 60 min, the brazed niobium alloy honeycomb panel and the honeycomb core remained separated, indicating no welding was achieved and no connection strength was found between the panel and the core.

[0053] When the Ti-Zr-V brazing filler coating thickness was increased to approximately 40 μm, the brazing temperature was 1600℃, and the holding time was 60 min, the panel / core did not separate after brazing, and there was a certain degree of connection strength between the panel and the honeycomb core. The brazing interface weld quality was tested using ultrasonic testing. The brazing interface weld rate was poor after brazing, and welding was not achieved. There was no connection strength between the board and the core.

[0054] When the thickness of the Ti-Zr-V solder coating is increased to about 50 μm, the brazing temperature is 1640℃, and the holding time is 60 min, the brazing panel / core bonding rate is slightly improved, but the bonding quality is still poor.

[0055] To address the issue of poor brazing weld ratio during Ti-Zr-V brazing of honeycomb, Nb element was further added to the Ti-Zr-V brazing filler metal, which improved the wetting and spreading properties between the brazing filler metal and the honeycomb core, achieving high-quality welding of Nb521 niobium alloy honeycomb, and preventing the production of low-melting-point eutectic phases at the brazing interface.

[0056] This invention employs a multi-principal element brazing alloy design method that introduces elements with positive enthalpy of mixing. Metal elements (typically Nb, with pairwise enthalpies of mixing shown in Table 3) with near-zero or slightly positive enthalpies of mixing are introduced into the Ti-Zr-V alloy matrix. This increases the ideal enthalpy of mixing of the alloy (typically greater than 0 kJ / mol) and reduces the reactivity between the brazing filler metal and the base metal. The method for calculating the ideal enthalpy of mixing of the alloy is as follows: Let c be the ideal enthalpy of mixing of the binary element pair consisting of the i-th and j-th elements. i and c j Let represent the atomic concentrations of the i-th and j-th elements in the alloy. Furthermore, by adjusting the multi-element alloy composition to make the ideal mixing configuration entropy of the alloy greater than 1 (as shown in Table 4), the ideal mixing configuration entropy of a multi-principal element medium-entropy alloy with near-zero or positive mixing enthalpy is calculated as follows: (R is the gas constant).

[0057] Table 3. Ideal mixing enthalpy of the two elements in the alloy (kJ / mol)

[0058] Nb Ti Zr V Nb 0 2 4 -1 Ti 2 0 0 -2 Zr 4 0 0 -4 V -1 -2 -4 0

[0059] Table 4. Mass composition of brazing alloy and its ideal enthalpy of mixing and entropy of mixing.

[0060] Ti Zr Cr V Nb <![CDATA[DS mix / R]]> <![CDATA[DH mix ]]> 1 70 15 - 15 - 0.706 -0.986 2 65 20 - 15 - 0.775 -0.987 3 60 30 - 10 - 0.802 -0.704 4 70 - 15 15 - 0.795 -3.973 5 65 - 20 15 - 0.865 -4.734 6 60 - 30 15 - 0.939 -5.742 7 63 13.5 - 13.5 10 0.887 -0.636 8 52.5 11.25 - 11.25 25 1.030 0.096 9 42 9 - 9 40 1.099 0.749

[0061] Based on the above calculation results, three types of Nb-Ti-Zr-V solders were prepared as shown in Table 5.

[0062] Table 5. Nb-Ti-Zr-V solder composition design (wt%)

[0063] Brazing filler number Nb Ti Zr V 7 10 63 13.5 13.5 8 25 52.5 11.25 11.25 9 40 42 9 9

[0064] Wetting tests were conducted on the brazing alloys with the brazing alloy composition shown in Table 5 under the process conditions of heating temperature 1600℃ and holding time 10min. As the Nb element increased, the wetting performance of the brazing alloy gradually decreased. The main reason is that the melting point of the alloy increases with the increase of Nb element.

[0065] As an optional implementation, the mass percentages of Nb, Ti, Zr, and V are 25%, 52.5%, 11.25%, and 11.25%, respectively.

[0066] Specifically, considering the calculated ideal mixing enthalpy and entropy values ​​for different Nb addition amounts, as well as the melting point and wettability of the brazing filler metal, a 25Nb-52.5Ti-11.25Zr-11.25V brazing filler metal was selected for niobium alloy honeycomb brazing. When the Nb-Ti-Zr-V brazing filler metal coating thickness was approximately 40–50 μm, the brazing temperature was 1620℃, and the holding time was 60 min, the structure of the niobium alloy honeycomb sandwich layer after brazing was as follows: Figure 4 As shown, the brazing result in a significantly improved panel / core bonding rate compared to Ti-Zr-V brazing filler metal.

[0067] This invention provides an Nb-Ti-Zr-V brazing filler metal coating for niobium alloy honeycomb brazing, comprising the aforementioned Nb-Ti-Zr-V brazing filler metal for niobium alloy honeycomb brazing. When the Nb-Ti-Zr-V brazing filler metal coating thickness is approximately 40–50 μm, the brazing temperature is 1620°C, and the holding time is 60 min, the brazing panel / core bonding rate is significantly improved compared to that of Ti-Zr-V brazing filler metal.

[0068] Figure 3 This is a schematic flowchart illustrating a method for preparing an Nb-Ti-Zr-V brazing filler metal coating for niobium alloy honeycomb brazing, as provided in an embodiment of the present invention. Figure 3 As shown, the method may include the following steps:

[0069] S100. Weigh out the corresponding mass of Nb, Ti, Zr and V metal elemental powder raw materials according to the mass percentage.

[0070] S200. Place the powders of each elemental metal in an electric arc melting equipment, evacuate to the first set value, then fill with ionized gas for melting, and after cooling in the furnace, prepare a brazing alloy ingot.

[0071] S300: Place the brazing alloy ingot and the niobium alloy panel in a vapor deposition apparatus, evacuate to the second set value, evaporate the brazing alloy ingot, and form a brazing coating on the surface of the niobium alloy panel.

[0072] In the above embodiments, due to the high melting point and poor amorphous forming ability of Nb-Ti-Zr-V solder, it cannot be prepared into foil-shaped solder. In order to obtain a niobium alloy panel with a uniform solder alloy coating, the project uses physical vapor deposition to prepare the solder coating.

[0073] As an optional implementation, the first setting value is 10. -3 The value is on the order of Pa. This value is a standard parameter in the electric arc melting process and will not be elaborated upon here.

[0074] As an optional implementation, the second setting value is 10. -3The value is on the order of Pa. This value is a standard parameter for vapor deposition processes and will not be elaborated upon here.

[0075] As an optional implementation method, the ionized gas is high-purity Ar. High-purity Ar possesses high electrical conductivity and flow properties.

[0076] Example 1

[0077] The composition of the solder (mass percentage): Ti 52.5%, Zr 11.25%, V 11.25%, Nb 25%.

[0078] Method for preparing solder coating:

[0079] (1) Weigh each element: Weigh the corresponding mass of the metal element powder raw material according to the mass percentage ratio, with a purity of 99.99%.

[0080] (2) Melting and preparing alloy ingots: The metal element powder weighed in step (1) is placed in an electric arc melting equipment and evacuated to 100°C. -3 The sample is in the Pa range, and then high-purity Ar is introduced as an ionizing gas. During the melting process, the sample is turned over at least 5 times to ensure the uniformity of the alloy composition. After cooling in the furnace, the prepared alloy ingot is taken out.

[0081] (3) Preparation of brazing filler metal coating: The alloy ingot prepared in step (2) is placed in a vapor deposition apparatus and evacuated to 10 °C. - 3 Pa-level evaporation of solder alloy ingots forms a solder coating on the surface of a niobium alloy panel with a thickness of approximately 40 μm.

[0082] The niobium alloy panel with brazing filler metal coating prepared by the above method was subjected to niobium alloy honeycomb brazing at a brazing temperature of 1650℃ and a brazing holding time of 60min. The microstructure of the brazed niobium alloy honeycomb interface is shown in Figure 5. Figure 5(a) shows the low magnification microstructure and Figure 5(b) shows the high magnification microstructure. After brazing, the panel and core are effectively connected.

[0083] It should be noted that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. The present invention is not limited to the specific steps and structures described above and shown in the figures. Furthermore, for the sake of brevity, detailed descriptions of known methods and techniques are omitted here.

[0084] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art without departing from the scope of the invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of this application should be included within the scope of the claims of this application.

Claims

1. A Nb-Ti-Zr-V filler metal for niobium alloy honeycomb brazing, characterized by, The Nb-Ti-Zr-V brazing filler metal comprises 25% of Nb, 52.5% of Ti, 11.25% of Zr and 11.25% of V by mass percentage, and the Nb is used to improve the wetting and spreading performance between the brazing filler metal and the honeycomb core.

2. A Nb-Ti-Zr-V braze coating for niobium alloy honeycomb brazing, characterized by, The Nb-Ti-Zr-V brazing filler metal for the Nb-alloy honeycomb brazing as claimed in claim 1.

3. The Nb-Ti-Zr-V braze alloy coating for niobium alloy honeycomb brazing according to claim 2, characterized by The coating thickness is 40-50 μm.

4. A method of producing a Nb-Ti-Zr-V braze coating for a niobium alloy honeycomb brazing as claimed in claim 2 or 3, characterized in that, The method comprises the following steps: The Nb, Ti, Zr and V metal element powder raw materials are weighed according to the mass percentage; The metal element powders are placed in an electric arc melting device, vacuumized to a first set value, then ionized gas is filled for melting, and after furnace cooling, the brazing filler metal alloy ingot is prepared; The brazing filler metal alloy ingot and the Nb-alloy panel are placed in a vapor deposition device, vacuumized to a second set value, the brazing filler metal alloy ingot is evaporated, and the brazing filler metal coating is formed on the surface of the Nb-alloy panel.

5. The method for preparing the Nb-Ti-Zr-V brazing filler metal coating for niobium alloy honeycomb brazing according to claim 4, characterized in that, The first set value is 10 -3 Pa order of magnitude.

6. The method for preparing the Nb-Ti-Zr-V brazing filler metal coating for niobium alloy honeycomb brazing according to claim 4, characterized in that, The second set value is 10 -3 Pa order of magnitude.

7. The method of claim 4, wherein the Nb-Ti-Zr-V braze coating for niobium alloy honeycomb brazing is prepared by the steps of: The ionized gas is high-purity Ar.

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