Si-ti combined micro-alloying method for sealing weld of molybdenum and molybdenum alloy ultra-high temperature heat pipe

Abstract

The application discloses a Si-Ti combined micro-alloying method for sealing welds of molybdenum and molybdenum alloy super-high-temperature heat pipes, which comprises the following steps: preparing Si-Ti mixed suspension liquid; filling the Si-Ti mixed suspension liquid into the joint of a workpiece to be welded; placing the workpiece to be welded in an inert gas protection atmosphere or a vacuum environment, and preheating the welding area of the workpiece to be welded by using a heating tool; welding the workpiece to be welded, and keeping the welding area of the workpiece after welding in the inert gas protection atmosphere or the vacuum environment, and then cooling to room temperature, so as to complete the Si-Ti combined micro-alloying of the weld of the workpiece. The application can ensure that the normal-temperature mechanical properties of the fusion welding joint are good, and can also generate Mo3Si phases in the weld, which can improve the high-temperature creep properties of the molybdenum and molybdenum alloy fusion welding joint, so that the high-temperature properties of the molybdenum and molybdenum alloy fusion welding joint are improved.

Description

Technical Field

[0001] This invention belongs to the field of welding technology and relates to a Si-Ti combined microalloying method for sealing welds of molybdenum and molybdenum alloy ultra-high temperature heat pipes. Background Technology

[0002] Molybdenum and its alloys possess excellent high-temperature mechanical properties, a small neutron absorption cross section, a low coefficient of thermal expansion, superior thermal conductivity, and good machinability. Furthermore, they exhibit good stability in air or water at temperatures below 1500℃. These advantages make molybdenum and its alloys crucial in metallurgy, aerospace, nuclear energy, and military fields.

[0003] However, molybdenum and its alloys are inherently hard and brittle materials with extremely poor weldability. The use of pure molybdenum is limited to its recrystallization temperature because after recrystallization, impurity elements tend to accumulate at the grain boundaries, thus losing their excellent high-temperature properties. Molybdenum alloys suffer from similar problems.

[0004] To improve the performance of molybdenum alloy welded joints, researchers often use Ti and Zr as alloying elements, which do indeed significantly improve the static mechanical properties of the joints at both room temperature and high temperature. However, the low melting points of Ti and Zr significantly reduce the weld metal's resistance to high-temperature creep, and can even increase the creep rate of the weld metal by an order of magnitude at high temperatures. These problems severely limit the application of molybdenum and molybdenum alloys in critical equipment such as space nuclear reactor power supplies. Summary of the Invention

[0005] The purpose of this invention is to solve the problems in the prior art and provide a Si-Ti combined microalloying method for ultra-high temperature heat pipe sealing welds of molybdenum and molybdenum alloys, thereby solving the problem of poor high-temperature performance of molybdenum and molybdenum alloy welds.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] A Si-Ti combined microalloying method for sealing welds of molybdenum and molybdenum alloy ultra-high temperature heat pipes includes:

[0008] Preparation of Si-Ti mixed suspension;

[0009] The Si-Ti mixed suspension is filled into the joint of the workpieces to be welded;

[0010] Place the workpiece to be welded in an inert gas protective atmosphere or a vacuum environment, and use a heating fixture to preheat the welding area of ​​the workpiece to be welded.

[0011] The workpiece is welded, and the welded area is kept warm in an inert gas protective atmosphere or vacuum environment after welding, and then cooled to room temperature to complete the Si-Ti combined microalloying of the workpiece weld.

[0012] Furthermore, the workpiece to be welded is a molybdenum alloy containing pure molybdenum and other alloying elements not exceeding 2 wt%, or a molybdenum alloy with a second-phase dopant content not exceeding 2 wt%.

[0013] Furthermore, it also includes pretreatment of the workpieces to be welded, which includes surface cleaning and adjustment of the joint gap.

[0014] Furthermore, the method for preparing the Si-Ti mixed suspension includes:

[0015] A mixture of Si and Ti powders was added to anhydrous ethanol at a mass ratio of 1:0.875 to 1.125, and then ultrasonically stirred until a Si-Ti mixed suspension was formed.

[0016] Furthermore, the purity of both the Si powder and the Ti powder is not less than 99.99%, the Si powder is an irregular powder with a particle size of less than 5 μm, the Ti powder is a spherical powder with a particle size of 5 to 15 μm, and the alcohol concentration in the anhydrous ethanol is not less than 99.5%.

[0017] Furthermore, the process of filling the Si-Ti mixed suspension is as follows:

[0018] The Si-Ti mixed suspension is repeatedly filled into the joint of the workpiece to be welded by dripping or pouring until the anhydrous ethanol in the Si-Ti mixed suspension evaporates and the mixed powder crystallizes and fills the gap at the joint.

[0019] Furthermore, the inert gas is argon with a purity of not less than 99.99%, and the vacuum environment has a vacuum degree of not less than 10. -2 Pa.

[0020] Furthermore, the preheating temperature is 400–600°C.

[0021] Furthermore, the welding is performed using laser welding, laser arc welding, argon arc welding, plasma beam welding, or electron beam welding.

[0022] Furthermore, the weld seam of the workpiece is a butt weld or a fillet weld.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] This invention provides a Si-Ti combined microalloying method for sealing welds of molybdenum and molybdenum alloy ultra-high temperature heat pipes. The method involves cleaning the surface of the "pipe-end plug" fitting area on the workpiece to be welded and adjusting the gap at the joint to an appropriate size. A prepared Si-Ti mixed suspension is then filled into the joint of the assembled workpiece. The workpiece is placed in an inert gas atmosphere or a vacuum environment, and the welding area is preheated. Appropriate welding parameters are selected based on the joint type and weld fusion ratio to complete the welding. The welded area is then held at a temperature of 10°C in an inert gas atmosphere or a vacuum environment and cooled to room temperature, thus completing the combined microalloying of the sealing weld of the molybdenum and molybdenum alloy ultra-high temperature heat pipe. This invention ensures good room-temperature mechanical properties of the welded joint while also generating a Mo3Si phase in the weld to improve the high-temperature creep resistance of the molybdenum alloy welded joint, thereby enhancing the high-temperature performance of the molybdenum and molybdenum alloy weld.

[0025] When a certain amount of Si and Ti are added to the weld zone of the joint, these two elements enter the molten pool along with the melting of the base metal. As the temperature of the molten pool decreases, the Mo matrix begins to solidify. When the temperature drops to 2025℃, the Mo3Si phase begins to form. As the temperature continues to decrease, the Ti5Si3 phase begins to form at 1170℃. The presence of the Mo3Si and Ti5Si3 phases can act as a second-phase strengthening agent at the grain boundaries. Among them, the Mo3Si content is relatively high and is dispersed in the weld. The Mo3Si crystal structure is A15. The hard Mo3Si particles have good high-temperature stability and maintain a coherent crystallographic relationship with the α-Mo matrix. The high elastic distortion energy near the Mo3Si particles has a strong ability to hinder dislocation movement and can also hinder grain boundary movement. Therefore, the dispersed Mo3Si phase formed in the weld zone can significantly improve the high-temperature creep strength of molybdenum and molybdenum alloy welds. As the temperature continues to decrease, MoO2 and TiO2 begin to form. The formation of TiO2 first reduces the O content in the weld, and secondly, it reduces the amount of harmful MoO2 phase. Using the method provided by this invention, the room temperature maximum tensile strength of the fusion-welded joints of molybdenum and molybdenum alloys can reach 300.8 MPa, and XRD analysis revealed the presence of a Mo3Si phase in the weld zone, which improves resistance to high-temperature creep. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a dimensional diagram of the molybdenum tube and end plug of the present invention.

[0028] Figure 2 This is a schematic diagram of the addition of Si-Ti mixed suspension in Embodiment 3 of the present invention.

[0029] Figure 3 The figures show the tensile curves of the Si-Ti alloyed joint and the unalloyed joint in Embodiment 3 of the present invention.

[0030] Figure 4 This is a microscopic image of the fracture location and fracture surface of the welded joint in Embodiment 3 of the present invention.

[0031] Figure 5 This is a cross-sectional view of the Si-Ti alloyed molybdenum tube-end plug laser welding joint in Embodiment 3 of the present invention.

[0032] Figure 6 The image shows the XRD results of the weld zone in the cross-section of the laser-welded joint of Si-Ti alloyed molybdenum tube-end plug in Embodiment 3 of the present invention.

[0033] Figure 7 The tensile strength diagrams are for microalloyed welded joints with different Si:Ti mass ratios according to the present invention.

[0034] Figure 8 This is a tensile stress-displacement curve of the microalloyed welded joints under different Si:Ti mass ratios according to the present invention.

[0035] in, Figure 1 (a) Dimensional diagram of the molybdenum tube in Example 3; (b) Dimensional diagram of the end plug in Example 3; Figure 4 (a) Microscopic image of the fracture location and fracture surface of the laser-welded joint of the unalloyed molybdenum tube-end plug in Example 3; Figure 4 (b) Microscopic images of the fracture location and fracture surface of the laser-welded joint of Si-Ti alloyed molybdenum tube-end plug in Example 3. Detailed Implementation

[0036] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0037] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0038] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0039] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0040] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0041] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0042] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0043] The present invention will now be described in further detail with reference to the accompanying drawings:

[0044] This invention provides a Si-Ti combined microalloying method for sealing welds of molybdenum and molybdenum alloy ultra-high temperature heat pipes, comprising the following steps:

[0045] Si-Ti powder mixtures with different mass ratios were crystallized and spread on a flat plate for powder-based self-fusion welding experiments, followed by tensile property tests. Tensile strength and tensile curves of the welded joints under different Si-Ti powder mass ratios were obtained. Based on these results, the average tensile strength of the joint was highest when the Si-Ti powder mass ratio was 1:0.875–1.125. Therefore, a Si-Ti powder mass ratio of 1:0.875–1.125 was selected as the preparation ratio for the Si-Ti mixed suspension. Si and Ti powders with a mass ratio of 1:0.875–1.125 were added to anhydrous ethanol and stirred to prepare the Si-Ti mixed suspension.

[0046] The purity of Si powder and Ti powder is not less than 99.99%. Si powder is an irregular powder with a particle size of less than 5 μm, and Ti powder is a spherical powder with a particle size of 5 to 15 μm. The alcohol concentration in anhydrous ethanol is not less than 99.5%.

[0047] The workpiece to be welded is made of pure molybdenum and a molybdenum alloy containing no more than 2 wt% of other alloying elements, or a molybdenum alloy with a second-phase dopant content of no more than 2 wt%. The surface of the area to be welded on the workpiece is cleaned as follows: the area is sanded with sandpaper, then rinsed with alkaline wash followed by water wash. Next, the area is ultrasonically cleaned in acetone, then removed and dried. The workpiece is made of molybdenum and a molybdenum alloy.

[0048] The Si-Ti mixed suspension is filled into the joint of the assembled workpiece to be welded. The Si-Ti mixed suspension is repeatedly filled into the joint of the workpiece to be welded by dripping and pouring until the anhydrous ethanol in the Si-Ti mixed suspension at the joint evaporates and the mixed powder crystallizes to fill the gap.

[0049] The workpiece to be welded shall be placed in an argon protective atmosphere with a purity of not less than 99.99% or a vacuum degree of not less than 10. -2 In a vacuum environment of Pa, the welding area of ​​the workpiece to be welded is preheated at 400-600°C using a heating fixture.

[0050] The welding heat source is placed at the welding joint of the workpieces to be welded, and then laser welding, laser arc welding, argon arc welding, plasma beam welding, or electron beam welding are used to complete the fusion welding of the workpieces. After welding, the welded area of ​​the workpiece is protected in an argon atmosphere with a purity of not less than 99.99% or a vacuum degree of not less than 10... -2The process involves heat treatment in a vacuum environment at 100 Pa, followed by cooling to room temperature, to complete the combined microalloying of the sealing weld of ultra-high temperature heat pipes for molybdenum and molybdenum alloys. After welding, the workpiece weld is either a butt weld or a fillet weld. The combined mass percentage of Si and Ti in the final weld is approximately 3.0 wt%, which can generate the Mo3Si phase in the weld, which is expected to improve the high-temperature creep performance of the welded joint of molybdenum and molybdenum alloys.

[0051] The present invention will be further described in detail below with reference to specific embodiments:

[0052] Example 1: Alloying and welding of "molybdenum plate" (Si:Ti = 3:2.6)

[0053] Taking the alloying laser welding of pure molybdenum "molybdenum plate" as an example, its dimensions are: 50mm×50mm×2mm.

[0054] The main welding process is as follows:

[0055] 1) Polish the molybdenum plate in sequence with 400#, 600#, 800# and 1000# sandpaper, then wash it with a low concentration of sodium hydroxide solution, and finally clean it with anhydrous ethanol using ultrasound and blow it dry for later use.

[0056] 2) According to the Si:Ti mass ratio of 3:2.6, 3g of Si powder with a purity of not less than 99.99% and 2.6g of Ti powder with a purity of not less than 99.99% are put into a container containing 3ml of anhydrous ethanol and stirred until a uniform Si-Ti mixed suspension is formed.

[0057] 3) The prepared Si-Ti mixed suspension was evenly coated on the surface of the molybdenum plate. After the anhydrous ethanol evaporated, welding was carried out. To avoid the impact of assembly gaps on joint performance, the self-fusion welding method was used for welding.

[0058] 4) The assembled sample to be welded was placed in a high-purity argon protective atmosphere. Then, the laser beam was irradiated onto the welding area of ​​the molybdenum plate filled with Si-Ti powder crystals. The laser power was p = 2800W, the defocusing amount f = 0, and the welding speed v = 1.2m / min to complete the Si-Ti alloying laser welding of the molybdenum plate. The workpiece was then allowed to cool slowly to room temperature under argon protection. The tensile strength of the joint was tested and found to be 213.2 MPa.

[0059] Example 2: Alloying and welding of "molybdenum plate" (Si:Ti = 3:3.5)

[0060] The difference from Example 1 is that, in the welding process, 3g of Si powder with a purity of not less than 99.99% and 3.5g of Ti powder with a purity of not less than 99.99% were successively added to a container containing 3ml of anhydrous ethanol in a Si:Ti mass ratio of 3:3.5, and stirred until a homogeneous Si-Ti mixed suspension was formed. The tensile strength of the joint was finally measured to be 228.9 MPa.

[0061] Example 3: Alloy laser welding of "molybdenum tube-end plug"

[0062] Taking the alloying laser welding of pure molybdenum "molybdenum tube-end plug" as an example, its dimensions are as follows: Figure 1 As shown, Figure 1 All units indicated are in mm; the main welding process is as follows:

[0063] 1) Grind the mating area of ​​the molybdenum tube and the end plug with 400#, 600#, 800# and 1000# sandpaper in sequence, then wash with a low concentration of sodium hydroxide solution, and finally clean with anhydrous ethanol using ultrasound and blow dry for later use.

[0064] 2) According to the Si:Ti mass ratio of 1:1, 1g of Si powder with a purity of not less than 99.99% and 1g of Ti powder with a purity of not less than 99.99% are put into a container containing 1ml of anhydrous ethanol and stirred until a uniform Si-Ti mixed suspension is formed.

[0065] 3) Assemble the molybdenum tube and the end plug, and use a thickness gauge to control the gap width between the molybdenum tube and the end plug to be within 0.2mm;

[0066] 4) Add the prepared Si-Ti mixed suspension dropwise into the gap between the molybdenum tube and the end plug, repeating the addition until the suspension dries and the mixed powder crystallizes to fill the gap. The addition method is as follows: Figure 2 As shown;

[0067] 5) Place the assembled sample to be welded in a high-purity argon protective atmosphere, and then preheat the area to be welded using a heating fixture. When the joint temperature reaches 600℃, hold it at that temperature for 600s. Then, irradiate the weld area between the molybdenum tube and the end plug, which is filled with Si-Ti powder crystals, with a laser beam. Weld using welding parameters of 2200W laser power, 0 defocusing, 5.4m / min welding speed, and 4.5s welding time to complete the Si-Ti alloy laser welding of the molybdenum tube and end plug. After welding, continue heating with the preheating source under argon protection for 15min, then reduce the preheating source power and hold the workpiece at 400℃ in an argon atmosphere for 5min, then reduce the preheating source power again and hold the workpiece at 200℃ in an argon atmosphere for 5min, then turn off the preheating source and allow the workpiece to cool slowly to room temperature under argon protection.

[0068] The Si-Ti alloyed welded joint was subjected to tensile testing, and the tensile curve is shown below. Figure 3 As shown, the maximum tensile strength of the Si-Ti alloyed laser-welded joint is 300.8 MPa. Half of the Si-Ti alloyed laser-welded joint fractured at the weld seam, and the other half fractured at the base metal. The fracture surface was predominantly cleavage fracture. Molybdenum alloys are intrinsically brittle materials with a ductile-brittle transition temperature higher than room temperature; therefore, cleavage fracture is the optimal result that can be obtained. Figure 4 As shown in (b), the combined mass percentage of Si and Ti alloying elements in the final weld is approximately 3.0 wt%. The cross-sectional morphology of the laser-welded joint after Si-Ti alloying and the XRD results of the weld zone are shown in (b). Figure 5 and Figure 6 As shown, the Mo3Si phase was detected in the weld, and the presence of this phase is expected to improve the high-temperature creep performance of the molybdenum alloy welded joint.

[0069] The above results demonstrate that the present invention can generate a Mo3Si phase that can improve the high-temperature performance of molybdenum and molybdenum alloy fusion welds while ensuring the strength of the molybdenum tube-end plug laser weld joint under room temperature conditions.

[0070] Comparative Example 1: Alloyless Laser Welding of "Molybdenum Tube-End Plug"

[0071] Taking the unalloyed laser welding of pure molybdenum "molybdenum tube-end plug" as an example, the laser welding material for unalloyed pure molybdenum molybdenum tube-end plug is the same as in Example 3, and the main welding process is as follows:

[0072] 1) Grind the mating area of ​​the molybdenum tube and the end plug with 400#, 600#, 800# and 1000# sandpaper in sequence, then wash with a low concentration of sodium hydroxide solution, and finally clean with anhydrous ethanol using ultrasound and blow dry for later use.

[0073] 2) Assemble the molybdenum tube and the end plug, with an assembly gap of less than 0.05 mm;

[0074] 3) Place the assembled sample to be welded in a high-purity argon protective atmosphere, and then use a heating fixture to preheat the area to be welded. When the joint temperature reaches 600℃, hold it at that temperature for 600s. Then, irradiate the molybdenum tube-end plug welding area with a laser beam. Weld with welding parameters of 2200W laser power, 0 defocusing, 5.4m / min welding speed, and 4.5s welding time to complete the alloy-free laser welding of the molybdenum tube-end plug. After welding, continue to heat the preheating source under argon protection for 15min. Then, reduce the preheating source power and keep the workpiece at 400℃ in an argon atmosphere for 5min. Then, reduce the preheating source power and keep the workpiece at 200℃ in an argon atmosphere for 5min. Finally, turn off the preheating source and allow the workpiece to cool slowly to room temperature under argon protection.

[0075] Tensile testing was performed on the unalloyed pure molybdenum laser-welded joint, and the tensile curve is shown below. Figure 3 As shown, the maximum tensile strength of the unalloyed laser-welded joint is 327.5 MPa. The fracture sites of the unalloyed laser-welded joint are mostly located in the center of the weld, and the fracture surface is mainly intergranular fracture, such as... Figure 4 As shown in (a).

[0076] Table 1. Comparison of tensile properties between Example 3 and Comparative Example 1

[0077]

[0078] As shown in Table 1, the maximum tensile strength of the Si-Ti alloyed laser-welded joint is 300.8 MPa, while that of the unalloyed laser-welded joint is 327.5 MPa, with little difference between the two. However, the fracture sites of the unalloyed laser-welded joint are mostly located in the center of the weld, while half of the Si-Ti alloyed laser-welded joints fracture at the weld seam, and the other half fracture in the better-performing base material region. Furthermore, the XRD results of the Si-Ti alloyed laser-welded joint are as follows... Figure 5 As shown, the Mo3Si phase was detected in the weld, and its presence is expected to improve the high-temperature creep performance of the molybdenum alloy welded joint. These results demonstrate that the present invention can generate the Mo3Si phase, which can enhance the high-temperature performance of molybdenum and molybdenum alloy fusion welds, while ensuring the strength of the molybdenum tube-end plug laser welded joint under room temperature conditions.

[0079] Comparative Example 2: Laser welding of pure molybdenum without alloying and with alloys of different Si / Ti mass ratios

[0080] Taking pure molybdenum alloy butt laser welding as an example, the laser welding material is the same as in Example 1, the molybdenum plate size is 50mm×50mm×2mm, and the main welding process is the same as in Example 1.

[0081] Si and Ti were added by using the same volume and solute mass fraction, but different mass ratios (Si:Ti mass ratios were 3:1, 3:2, 3:3, 3:4, 3:5, 3:6, 3:7, and 3:8, with a blank control test conducted without Si and Ti powder) of Si and Ti powder. Anhydrous ethanol was added and thoroughly stirred to form a Si-Ti mixed suspension, which was then uniformly coated onto the surface of a molybdenum plate. Welding was performed after the anhydrous ethanol had evaporated. Welding parameters were: laser power P = 2800W, welding speed v = 1.2m / min, and defocusing amount f = 0mm. To avoid the influence of assembly gaps on joint performance, self-fusion welding was used, with argon gas protection during the welding process. After welding, tensile specimens were cut at each mass ratio. Tensile tests were conducted on the self-fusion welded joints without alloying and with eight different Si:Ti alloying elements. The tensile strength results and tensile curves are shown below. Figure 7 and Figure 8 As shown. From Figure 7 and Figure 8 As can be seen, the tensile strength of alloyed joints with different Si:Ti ratios is higher than that of unalloyed joints. Furthermore, as the proportion of Ti content increases, the tensile strength of the joints first increases and then decreases. The tensile curves indicate that the fracture mode of all joints is brittle fracture. When Si:Ti = 3:3, the combined mass percentage of Si and Ti alloying elements in the final weld is approximately 3.0 wt%, and the average tensile strength reaches its highest value of 231.6 MPa, which is 4.8 times that of the unalloyed joint (48.0 MPa).

[0082] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A Si-Ti combination microalloying method for sealing weld of molybdenum and molybdenum alloy ultra-high temperature heat pipe, characterized in that, include: Preparation of Si-Ti mixed suspension; The Si-Ti mixed suspension is filled into the joint of the workpieces to be welded; Place the workpiece to be welded in an inert gas protective atmosphere or a vacuum environment, and use a heating fixture to preheat the welding area of ​​the workpiece to be welded. Welding is performed on the workpiece to be welded. After welding, the welded area of ​​the workpiece is kept warm in an inert gas protective atmosphere or vacuum environment, and then cooled to room temperature to complete the Si-Ti combined microalloying of the workpiece weld. The method for preparing the Si-Ti mixed suspension includes: Si powder and Ti powder with a mass ratio of 1:0.875~1.125 were added to anhydrous ethanol and then ultrasonically stirred until a Si-Ti mixed suspension was formed. When the temperature drops to 2025°C, the Mo3Si phase begins to form. As the temperature continues to drop, the Ti5Si3 phase begins to form at 1170°C. The presence of the Mo3Si and Ti5Si3 phases can play a second-phase strengthening role at the grain boundaries, with the Mo3Si phase being dispersed in the weld.

2. The Si-Ti combination micro-alloying method for sealing weld of molybdenum and molybdenum alloy ultra-high temperature heat pipe according to claim 1, characterized in that, The workpiece to be welded is a molybdenum alloy containing pure molybdenum and other alloying elements not exceeding 2 wt%, or a molybdenum alloy with a second-phase dopant content not exceeding 2 wt%.

3. The Si-Ti combination micro-alloying method of sealing weld of molybdenum and molybdenum alloy ultra-high temperature heat pipe according to claim 1, characterized in that, It also includes pretreatment of the workpiece to be welded, which includes surface cleaning and adjustment of the joint gap.

4. The Si-Ti combination micro-alloying method of sealing weld of molybdenum and molybdenum alloy ultra-high temperature heat pipe according to claim 1, characterized in that, The purity of both Si powder and Ti powder is not less than 99.99%, the Si powder is an irregular powder with a particle size of less than 5 μm, the Ti powder is a spherical powder with a particle size of 5~15 μm, and the alcohol concentration in the anhydrous ethanol is not less than 99.5%.

5. The Si-Ti combination micro-alloying method of sealing weld of molybdenum and molybdenum alloy ultra-high temperature heat pipe according to claim 1, characterized in that, The process of filling the Si-Ti mixed suspension is as follows: The Si-Ti mixed suspension is repeatedly filled into the joint of the workpiece to be welded by dripping or pouring until the anhydrous ethanol in the Si-Ti mixed suspension evaporates and the mixed powder crystallizes and fills the gap at the joint.

6. The Si-Ti combination micro-alloying method of sealing welds of molybdenum and molybdenum alloys super-high temperature heat pipes according to claim 1, characterized in that, The inert gas is argon with purity not less than 99.99%, and the vacuum environment is vacuum degree not less than 10 -2 Pa.

7. The Si-Ti combination micro-alloying method of sealing welds of molybdenum and molybdenum alloy ultra-high temperature heat pipes according to claim 1, characterized in that, The preheating temperature is 400~600°C.

8. The Si-Ti combination micro-alloying method of sealing welds of molybdenum and molybdenum alloys super-high temperature heat pipes according to claim 1, characterized in that, The welding is performed using laser welding, laser arc welding, argon arc welding, plasma beam welding, or electron beam welding.

9. The Si-Ti combination micro-alloying method of sealing welds of molybdenum and molybdenum alloy ultra-high temperature heat pipes according to claim 1, characterized in that, The weld seam of the workpiece is either a butt weld or a fillet weld.

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