High-niobium alloy gradient functional material based on double-laser melting forging and preparation method of high-niobium alloy gradient functional material

Abstract

The invention belongs to the technical field of laser manufacturing and remanufacturing, and particularly relates to a high-niobium alloy gradient functional material based on double-laser melting forging and a preparation method of the high-niobium alloy gradient functional material. The high-niobium alloy gradient functional alloy material comprises the following components in percentage by mass: 0.03%-0.06% of C, 1.2%-1.8% of Mn, 0.2%-0.3% of Nb, 0.09%-0.15% of Si, 0.2%-0.5% of Cr, 0.1%-0.5% of Ni, 0.1%-0.5% of Ce, 0.2%-0.5% of Ti, 0.02%-0.05% of La and the balance of Fe. Compared with composite processes such as surfacing and spraying, the method is flexible to operate, a metallurgical bonding layer without cracks with the base body is achieved without limitation of types and thicknesses of metal materials and materials of the base body, the metallurgical quality of a cladding layer with a small heat affected zone of the base body is high, pores and inclusions with the sizes larger than 20 micrometers do not exist, and the method is far superior to a surfacing repairing technology commonly used for petroleum pipelines at present; the three-in-one target of high toughness, low risk and long service life of petroleum pipeline repair is further achieved, and the method has remarkable industrial application value.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser manufacturing and remanufacturing, and particularly relates to a high-niobium alloy gradient functional material based on double-laser melt forging and a preparation method thereof. Background Art

[0002] To meet the demand for large oil and gas transportation volume and reduce pipeline construction costs, the current mainstream technologies at home and abroad adopt high steel grades such as X80 and large diameters, which has become the development trend of the world's oil and gas pipelines; China has built 40,000 kilometers of high steel grade and large diameter (outer diameter 1219mm, 1422mm) pipelines and become a leader in high steel grade pipeline construction. Among them, 12,000 kilometers of X80 pipelines account for more than 50% of the world's total mileage. Existing X80 steel has problems such as tissue deterioration and ductility damage during use. Research work has shown that mainly due to the large heat input energy during the welding process of X80 steel, tissue deterioration occurs, and macroscopically, the impact toughness of the X80 tissue drops sharply.

[0003] At present, the welding repair of X80 mainly relies on traditional surfacing repair. The traditional surfacing repair has high heat input, serious coarsening of the heat affected zone (HAZ), and residual stress accumulation leading to safety risks. Moreover, the toughness of the joint drops by 30% - 40% after repair. Not only that, there are safety hazards in this repair method in long-distance natural gas pipelines. Due to the large heat input of surfacing, in order to prevent overheating of the pipe wall during the repair process, it is necessary to reduce the pressure during the repair process, which not only reduces the transportation operation efficiency but also has safety hazards and is prone to serious accidents.

[0004] In the prior art, a single laser cladding or mechanical forging process is difficult to balance low heat input and tissue regulation; niobium elements are very effective in increasing the non-recrystallization temperature of materials. However, under the condition of low carbon content (such as 0.04%) in X80 steel, the solubility of niobium elements in steel has obvious limitations, usually not more than 0.12%. This is mainly due to the heat input mode of traditional welding processes, which have large heat input and slow cooling rates, resulting in the appearance of coarse granular bainite regions in the material structure, and at the same time, the M + A structure also coarsens accordingly. Such adverse changes in the microstructure seriously affect the comprehensive properties of the material, such as strength, toughness, and fatigue resistance.

[0005] In summary, conventional welding processes cannot effectively control the heat input linear energy, are difficult to meet the requirement of increasing the solubility of niobium elements in a low-carbon environment, and thus limit the exertion of the superior properties of high-niobium alloys in steel materials. Therefore, it is of great practical significance to develop a new preparation process to overcome the above problems and prepare a high-niobium alloy gradient functional material with excellent properties. Summary of the Invention

[0006] To solve the problems of high heat input, low niobium solid solubility, and coarse structure in traditional manufacturing and welding repair, the present invention provides a high-niobium alloy gradient functional material based on double-laser forging and its preparation process. By means of a high-energy laser beam, while cladding a cladding layer on the surface of the substrate, laser shock peening is supplemented to achieve the "double strengthening" effect. The metallurgical bonding between the substrate and the strengthening layer does not affect the material of the substrate, and the overall fatigue performance can be improved. By designing the powder material and combining the "double-laser time-sequence coupling" forging technology, a high-performance special forging repair layer is prepared on the service surface of the long-distance oil pipeline. Compared with the X80 pipeline steel material and the traditional repair method, the service life and safety reliability of the material in service are further improved.

[0007] Compared with composite processes such as surfacing and spraying, the method of the present invention is flexible in operation, is not limited by the type, thickness of the metal material and the material of the substrate, and can achieve a crack-free metallurgical bonding layer with the substrate. The heat-affected zone of the substrate is small, the metallurgical quality of the cladding layer is high, and there are no pores and inclusions larger than 20μm, which is far superior to the surfacing repair technology commonly used in oil pipelines at present. Further, the trinity goal of "high strength and toughness, low risk, and long life" for oil pipeline repair is achieved, and it has significant industrial application value.

[0008] To achieve the above object, the present invention adopts the following technical solutions.

[0009] A high-niobium alloy gradient functional alloy material based on double-laser forging, comprising the following components in mass percentages: 0.03%-0.06% C, 1.2%-1.8% Mn, 0.2%-0.3% Nb, 0.09%-0.15% Si, 0.2%-0.5% Cr, 0.1%-0.5% Ni, 0.1%-0.5% Ce, 0.2%-0.5% Ti, 0.02-0.05% La, and the balance is Fe.

[0010] A preparation method of a high-niobium alloy gradient functional material based on double-laser forging, comprising the following steps: Step 1, substrate pretreatment; Step 2, start the double-laser system and perform double-laser time-sequence coupling on the substrate in Step 1 using the above alloy material; Step 3, perform post-treatment on the material processed in Step 2 to obtain a high-niobium alloy gradient functional material based on double-laser forging with X80 as the substrate.

[0011] Further, Step 1 is specifically: surface grinding and cleaning the X80 material to be processed (carbon content 0.04%) to remove impurities such as oil stains and oxide scales on the surface, ensuring the surface cleanliness of the material to facilitate the effective absorption and transmission of energy during the subsequent laser processing.

[0012] Furthermore, in step 2, the dual-laser system includes two lasers with independent control systems. One is the front laser cladding unit: a high-power continuous fiber laser, equipped with a coaxial powder feeding cladding head; the other is the rear laser forging unit: a high-energy short-pulse laser, equipped with a focusing mirror; a high-precision laser optical path adjustment system and a working platform capable of precisely controlling the moving speed are provided to ensure that the laser beam can accurately act on the material surface; a five-axis linkage numerical control machine tool (positioning accuracy ±5μm) is used, carrying a cladding head and a forging head (the included angle is 30°–60°, and the spacing is 5–20mm); an infrared thermal imager is used to monitor the temperature field of the molten pool in real time, and a high-speed CCD camera (10 4 fps) is used to observe the dynamics of the molten pool (size, flow behavior), and an optoelectronic sensor is used to detect the position of the solidification front of the cladding layer.

[0013] Furthermore, in step 2, the power of the front laser cladding is 1.5–3 kW in continuous wave, the spot size is φ2-4mm, the scanning speed is 10-50mm / s, and the protective gas flow rate: argon 15-25L / min; the energy of the rear laser forging is 5–20 J, the pulse frequency is 10–50 kHz, the pulse width is 10-50ns, and the spot size is φ 0.4-2mm (focused spot); the time sequence interval between the front and rear lasers is set to 50-300ns, with the same cladding speed (rigid synchronization), helium (5–10 L / min, to prevent plasma), and the stability of the dual-laser time sequence coupling is ensured through an accurate control system; during the laser melting and forging process, the moving speed of the working platform is controlled to be 5-20mm / s, so that the laser beam forms a continuous action trajectory on the material surface; the scanning method of laser melting and forging adopts spiral scanning, and the scanning spacing is 0.1-0.3mm to ensure that the material surface can be evenly affected by laser melting and forging to form a gradient compressive stress; during the whole processing process, the heat input linear energy is strictly controlled, and the heat input linear energy is controlled within 10-30J / mm to avoid problems such as coarse grains caused by excessive heat input.

[0014] Furthermore, a forging time window is also set in step 2. The existence time of the molten pool needs to be calculated according to the thermal physical properties of the material; 0.5–3 ms before the solidification of the molten pool, the forging timing is triggered, and the time interval Δt: 10 μs–10 ms; a timing synchronization controller—a high-precision digital signal generator is configured to achieve dual-laser trigger delay control (accuracy ±1 μs).

[0015] Furthermore, step 3 is specifically as follows: The material processed in step 2 is naturally cooled to room temperature in the air, and then stress relief annealing treatment is carried out. The annealing temperature is 500-600°C, and the holding time is 1-2h to eliminate the residual stress inside the material and further stabilize the microstructure and properties of the material.

[0016] The mechanism of the present invention is as follows: 1. High niobium solid solution mechanism and its influence on material properties: The dual-laser time-sequential coupling process forms an instantaneously high-temperature and high-energy-density region on the material surface by precisely controlling the energy, pulse parameters, and time interval of the two laser beams. After the first laser beam forms a molten pool, the timely action of the second laser beam enables the atoms in the molten pool to obtain higher energy, greatly enhancing the diffusion ability of niobium atoms in the matrix. Compared with traditional welding processes, this dual-laser synergistic effect allows more niobium elements to break through the solid solution limit and dissolve into the low-carbon steel matrix within an extremely short time. The solid solution of niobium elements in the matrix can produce significant strengthening effects. On the one hand, niobium atoms form a solid solution with iron atoms, resulting in solid solution strengthening, increasing the resistance to dislocation movement, and thus effectively improving the strength of the material. On the other hand, the dissolved niobium elements can refine the grains, further enhancing the strength and toughness of the material through the grain boundary strengthening mechanism. At the same time, due to the solid solution of more niobium elements, the phase composition of the material also undergoes favorable changes, inhibiting the formation of coarse granular bainite and M + A structures, making the microstructure of the material more uniform and fine, and significantly improving the comprehensive properties of the material.

[0017] 2. Dynamic recrystallization and gradient compressive stress formation mechanism: The dual-laser time-sequential coupling technology can trigger the continuous dynamic recrystallization mechanism during the material processing. Under the rapid action of the laser energy, strong temperature gradients and strain gradients are generated inside the material, causing a sharp increase in the dislocation density inside the material. When the dislocation density reaches a certain level, continuous dynamic recrystallization begins to occur inside the material under high-temperature and high-strain conditions, forming a large number of small and equiaxed new grains. This new microstructure formation mechanism further optimizes the mechanical properties of the material, improving the plasticity and toughness of the material. At the same time, during the laser forging process, the impact of the laser energy on the material surface generates dynamic pressure. Due to the uneven distribution of the laser energy on the material surface, the energy gradually decays from the surface to the interior, resulting in a greater degree of deformation on the material surface than inside, thus forming a gradient compressive stress, with a larger compressive stress on the surface and gradually decreasing towards the interior. This gradient compressive stress distribution can effectively offset the tensile stress borne by the material during service, significantly improving the fatigue resistance and service life of the material. In traditional processes, it is difficult to achieve such precise control of dynamic recrystallization and the formation of gradient compressive stress, which is an important innovative advantage of the process method of the present invention.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows.

[0019] 1. Significantly increased the solid solubility of niobium elements in low-carbon steel materials, breaking through the limitation of the niobium solid solubility not exceeding 0.12% under traditional processes, and enabling the solid solubility of niobium elements in the matrix to reach 0.2 - 0.3%, which is 2 - 3 times the niobium content in traditional manufacturing; through various mechanisms such as solid solution strengthening, grain refinement, and phase composition optimization, the strength, toughness, and comprehensive mechanical properties of the material have been greatly improved.

[0020] Among them, in addition to the conventional specific functions, the material components also have some specific synergistic effects: A. The Ti-Ce composite purifies the molten pool, providing an ultra-clean matrix environment for high Nb solid solution; B. The Mn-Si combination optimizes the fluidity of the molten pool, and cooperates with the high-energy beam of the dual laser to achieve precise control of the composition gradient; C. The Cr-Ni combination forms a nanocrystalline / amorphous composite passivation layer under rapid laser non-equilibrium solidification, breaking through the trade-off between corrosion resistance and strength of traditional stainless steels.

[0021] 2. The continuous dynamic recrystallization mechanism triggered by the dual-laser time-sequential coupling technology enables the material to form fine and equiaxed new grains, further improving the plasticity and toughness of the material, and providing better performance guarantee for the application of the material under complex working conditions.

[0022] 3. The gradient compressive stress distribution formed by the coordination of methods and parameters during the laser melt forging effectively offsets the tensile stress during the service of the material, significantly improving the fatigue resistance and service life of the material, and broadening the application range of the material.

[0023] 4. The preparation process method of the present invention has good controllability and repeatability. By precisely setting the laser parameters, processing parameters, and heat input line energy, a high-Nb alloy gradient functional material with excellent performance can be stably prepared, which is suitable for large-scale industrial production applications. Description of the Drawings

[0024] Figure 1 It is the microstructure diagram of Example 1.

[0025] Figure 2 It is the microstructure diagram of Comparative Example 1. Detailed Embodiments

[0026] The technical solutions and drawings in the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0027] A high-Nb alloy gradient functional alloy material based on dual-laser melt forging includes the following components in mass percentages: 0.03%-0.06% C, 1.2%-1.8% Mn, 0.2%-0.3% Nb, 0.09%-0.15% Si, 0.2%-0.5% Cr, 0.1%-0.5% Ni, 0.1%-0.5% Ce, 0.2%-0.5% Ti, 0.02-0.05% La, and the balance is Fe.

[0028] A preparation method of a high-niobium alloy functionally graded material based on dual-laser melting forging, comprising the following steps: Step 1, substrate pretreatment: The X80 material to be processed (carbon content 0.04%) is surface-ground and cleaned to remove impurities such as oil stains and scale on the surface, ensuring the surface cleanliness of the material to facilitate the effective absorption and transmission of energy during subsequent laser processing; Step 2, start the dual-laser system to perform dual-laser time-sequence coupling on the substrate in Step 1 using the above alloy material; the power of the pre-laser cladding is continuous wave 1.5–3 kW, the spot size is φ2-4mm, the scanning speed is 10-50mm / s, the shielding gas flow rate: argon 15-25L / min; the energy of the post-laser forging is 5–20 J, the pulse frequency is 10–50 kHz, the pulse width is 10-50ns, the spot size is φ 0.4-2mm (focused spot); the time-sequence interval between the front and rear lasers is set to 50-300ns, the same cladding speed (rigid synchronization), helium (5–10 L / min, anti-plasma), and the stability of the dual-laser time-sequence coupling is ensured through an accurate control system; during the laser melting forging process, control the moving speed of the working platform to be 5-20mm / s to make the laser beam form a continuous action trajectory on the material surface; the scanning method of the laser melting forging adopts a spiral scanning method, and the scanning pitch is 0.1-0.3mm to ensure that the material surface can be evenly affected by the laser melting forging to form a gradient compressive stress; during the whole processing process, strictly control the heat input linear energy, and the heat input linear energy is controlled within 10-30J / mm to avoid problems such as coarse grains caused by excessive heat input; Step 3, post-treatment of the material processed in Step 2: The material processed in Step 2 is naturally cooled to room temperature in the air, and then stress relief annealing treatment is carried out. The annealing temperature is 500-600°C, and the holding time is 1-2h to eliminate the residual stress inside the material and further stabilize the microstructure and properties of the material; obtain a high-niobium alloy functionally graded material with X80 as the substrate by dual-laser melting forging.

[0029] Furthermore, in Step 2, the dual-laser system includes two lasers with independent control systems. One is a pre-laser cladding unit: a high-power continuous fiber laser, equipped with a coaxial powder feeding cladding head; the other is a post-laser forging unit: a high-energy short-pulse laser, equipped with a focusing mirror; equipped with a high-precision laser optical path adjustment system and a working platform that can accurately control the moving speed to ensure that the laser beam can accurately act on the material surface; adopt a five-axis linkage numerically controlled machine tool (positioning accuracy ±5μm), equipped with a cladding head and a forging head (the included angle is 30°–60°, the spacing is 5–20mm); use an infrared thermal imager to monitor the temperature field of the molten pool in real time, and adopt a high-speed CCD camera (10 4Observe the dynamic state of the molten pool (size, flow behavior) at a frequency of

[0030] Further, in step 2, a forging time window is also set, and the existence time of the molten pool needs to be calculated according to the thermal physical properties of the material; 0.5 - 3 ms before the molten pool solidifies, trigger the forging timing, and the time interval Δt is 10 μs - 10 ms; configure a timing synchronization controller - a high-precision digital signal generator to achieve dual-laser trigger delay control (precision ±1 μs).

[0031] Example 1.

[0032] A high-niobium alloy gradient functional powder based on dual-laser forging is composed of the following components by mass percentage: 0.04% C, 1.2% Mn, 0.2% Nb, 0.09% Si, 0.2% - 0.5% Cr, 0.1% Ni, 0.2% Ce, 0.5% Ti, 0.02% La, and the balance is Fe.

[0033] Equipment and material preparation: Select two high-power lasers produced by IPG. Equip with a high-precision laser optical path adjustment system from Newport and a working platform from Zaber that can precisely control the moving speed. Prepare an X80 pipe material to be repaired with dimensions of 100mm × 50mm × 10mm, and its carbon content is 0.04%.

[0034] A preparation method of a high-niobium alloy gradient functional material based on dual-laser forging includes the following steps: Step 1: Use sandpaper to polish the surface of the low-carbon X80 material to remove the surface oxide scale, then put the material into an acetone solution and ultrasonically clean it for 15 minutes to remove the surface oil stain, take it out and dry it with nitrogen.

[0035] Step 2: Turn on the front laser, use the above functional powder to act on the surface of the X80 material to form a molten pool. The front laser cladding power is 2kW, the spot size is φ2mm, the scanning speed is 20mm / s, and the protective gas volume is 15L / min of argon; turn on the rear laser, the rear laser forging energy is 5J, the pulse frequency is 10kHz, the pulse width is 20ns, and the spot diameter is 0.8mm; the timing interval between the two lasers is set to 100ns; the moving speed of the working platform is set to 10mm / s, and the laser forging scanning method is spiral scanning with a scanning pitch of 0.2mm, and the heat input linear energy is controlled at 15J / mm; the two lasers act on the molten pool synergistically to promote the solid solution of niobium elements. During the laser forging process, the laser energy impacts the material surface to form a gradient compressive stress.

[0036] Step 3: Naturally cool the material processed in Step 2 to room temperature in the air, and then put it into a box-type resistance furnace for stress relief annealing treatment. The annealing temperature is 550 °C, and the holding time is 1.5 h to obtain a high-niobium alloy gradient functional material with X80 as the substrate by double laser melting and forging.

[0037] Performance testing: Detect the solid solubility of niobium element in the material by electron probe microanalysis (EPMA). The results show that the solid solubility of niobium reaches 0.25%. Observe the microstructure of the material using a scanning electron microscope (SEM). Fine and uniform microstructures can be seen, and no coarse granular bainite and coarsened M+A microstructures appear, as Figure 1 shown. Test the toughness of the material using an impact toughness testing machine. The results show that: when performing the impact toughness test on the surface melting and forging zone, the result is 40 J / cm²; when performing the impact toughness test in the middle to transition zone, the result is 31 J / cm²; when performing the impact toughness test near the substrate zone, the result is 22 J / cm²; based on the above test results, a high-niobium alloy gradient function design is realized. Use a Rockwell hardness tester to test the surface layer of the melting and forging microstructure, and the hardness reaches 57 HRC; when testing at different positions in the middle to transition zone and the substrate of the melting and forging, the hardness shows a gradient change gradually decreasing from the surface layer to the substrate. The hardness in the transition zone is about 50 HRC, and the hardness of the substrate is 43 HRC; compared with the material prepared by the traditional process, the fatigue life is increased by 2.5 times.

[0038] Example 2.

[0039] A high-niobium alloy gradient functional powder based on double laser melting and forging is composed of the following components by mass percentage: 0.04% C, 1.2% Mn, 0.2% Nb, 0.09% Si, 0.2% - 0.5% Cr, 0.1% Ni, 0.2% Ce, 0.5% Ti, 0.02% La, and the balance is Fe.

[0040] Equipment and material preparation: Select a high-power laser from Coherent. Equip a high-precision laser optical path adjustment system from Newport and a working platform from Zaber that can precisely control the moving speed. Prepare X80 low-carbon steel to be repaired with dimensions of 120 mm × 60 mm × 12 mm, and its carbon content is 0.04%.

[0041] A preparation method of a high-niobium alloy gradient functional material based on double laser melting and forging includes the following steps: Step 1: Use sandpaper to polish the surface of the low-carbon X80 material to remove the surface oxide scale. Then put the material into an acetone solution for ultrasonic cleaning for 15 min to remove the surface oil stain. After taking it out, dry it with nitrogen.

[0042] Step 2: Turn on the front laser, and make the above-mentioned functional powder act on the surface of X80 material to form a molten pool. The power of the front laser cladding is 2.2 kW, the spot size is φ2.2 mm, the scanning speed is 25 mm / s, and the protective gas volume is 15 L / min of argon; turn on the rear laser, the forging energy of the rear laser is 10 J, the pulse frequency is 15 kHz, the pulse width is 25 ns, and the spot diameter is 1.0 mm; the time sequence interval of the two lasers is set to 150 ns; the moving speed of the working platform is set to 15 mm / s, and the laser melting and forging scanning method is spiral scanning, the scanning pitch is 0.25 mm, and the heat input linear energy is controlled at 20 J / mm; the two lasers act synergistically on the molten pool to promote the solid solution of niobium element. During the laser melting and forging process, the laser energy impacts the material surface to form a gradient compressive stress.

[0043] Step 3: Naturally cool the material processed in Step 2 to room temperature in the air, and then put it into a box-type resistance furnace for stress relief annealing treatment. The annealing temperature is 600 °C, and the holding time is 1.0 h to obtain a high-niobium alloy gradient functional material with double laser melting and forging based on X80 as the substrate.

[0044] Performance testing: The solubility of niobium element in the material is detected by electron probe microanalysis (EPMA), and the result shows that the niobium solubility reaches 0.28%. The toughness of the material is tested by an impact toughness testing machine, and the results show that: the impact toughness test is carried out in the surface layer forging area, and the result is 45 J / cm²; the impact toughness test is carried out in the middle area, and the result is 30 J / cm²; the impact toughness test is carried out in the substrate area, and the result is 19 J / cm²; based on the above test results, the high-niobium alloy gradient function design is realized. The surface layer of the forging structure is tested by a Rockwell hardness tester, and the hardness reaches 56 HRC; different positions in the middle to transition area and the substrate of the forging are tested, and the hardness shows a gradient change gradually decreasing from the surface layer to the substrate. The hardness of the transition area is about 51 HRC, and the hardness of the substrate is 44 HRC. Compared with the materials prepared by traditional processes, the fatigue life is increased by 3 times.

[0045] Comparative Example 1.

[0046] Equipment and material preparation: Use a traditional arc welding equipment with the model of MIG-500. The material is low-carbon steel with the same size and carbon content as that in Example 1.

[0047] Welding process: Weld according to the conventional welding process parameters. The welding current is 180 A, the welding voltage is 22 V, the welding speed is 8 mm / s, and the heat input linear energy is about 50 J / mm.

[0048] Performance testing: The niobium solubility detected by EPMA is only 0.1%. SEM observes obvious coarse granular bainite and coarsened M+A structure, such as Figure 2As shown. The fatigue test shows that the fatigue resistance life of the material is much lower than that of the materials prepared in Example 1 and Example 2.

[0049] By comparing Example 1, Example 2 and Comparative Example 1, it can be clearly seen that the preparation process method of the present invention based on double laser forging has significant advantages in improving the niobium solid solubility, optimizing the microstructure and enhancing the material properties.

[0050] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A high-niobium alloy gradient functional alloy material based on dual laser melting forging, characterized in that It includes the following components by mass percentage: 0.03% - 0.06% C, 1.2% - 1.8% Mn, 0.2% - 0.3% Nb, 0.09% - 0.15% Si, 0.2% - 0.5% Cr, 0.1% - 0.5% Ni, 0.1% - 0.5% Ce, 0.2% - 0.5% Ti, 0.02 - 0.05% La, and the balance is Fe.

2. A preparation method of a high-niobium alloy gradient functional material based on double laser melting forging, characterized in that, It includes the following steps: Step 1, substrate pretreatment; Step 2, start the dual-laser system and perform dual-laser time-sequence coupling on the substrate in Step 1 using the above alloy material; Step 3, post-treat the material processed in Step 2 to obtain a high-niobium alloy gradient functional material with X80 as the substrate by dual-laser melting and forging.

3. The preparation method of the high-niobium alloy gradient functional material based on double laser melting forging according to claim 2, wherein, The specific content of Step 1 is: grind and clean the surface of the X80 material to be processed to remove impurities such as oil stains and oxide scales on the surface.

4. The preparation method of the high-niobium alloy gradient functional material based on dual laser melting and forging according to claim 2, wherein, In Step 2, the dual-laser system includes two lasers with independent control systems. One is a pre-laser cladding unit: a high-power continuous fiber laser equipped with a coaxial powder feeding cladding head; the other is a post-laser forging unit: a high-energy short-pulse laser equipped with a focusing mirror; it is equipped with a high-precision laser optical path adjustment system and a working platform that can accurately control the moving speed to ensure that the laser beam can accurately act on the material surface; a five-axis linkage numerical control machine tool is used, and the included angle between the cladding head and the forging head is 30° - 60°, and the spacing is 5 - 20 mm; an infrared thermal imager is used to monitor the temperature field of the molten pool in real time, a high-speed CCD camera is used to observe the dynamics of the molten pool, and a photoelectric sensor is used to detect the position of the solidification front of the cladding layer.

5. The preparation method of the high-niobium alloy gradient functional material based on dual laser melting forging according to claim 2, characterized in that, In Step 2, the power of the pre-laser cladding is continuous wave 1.5 - 3 kW, the spot size is φ2 - 4 mm, the scanning speed is 10 - 50 mm / s, and the protective gas flow rate: argon 15 - 25 L / min; the energy of the post-laser forging is 5 - 20 J, the pulse frequency is 10 - 50 kHz, the pulse width is 10 - 50 ns, and the spot size is φ0.4 - 2 mm; the time interval between the front and rear lasers is set to 50 - 300 ns, the same as the cladding speed, 5 - 10 L / min helium gas, and the stability of the dual-laser time-sequence coupling is ensured through an accurate control system; during the laser melting and forging process, the moving speed of the working platform is controlled at 5 - 20 mm / s; the scanning method of the laser melting and forging is spiral scanning, and the scanning spacing is 0.1 - 0.3 mm; during the whole processing process, the heat input linear energy is strictly controlled, and the heat input linear energy is controlled at 10 - 30 J / mm.

6. The preparation method of the high-niobium alloy gradient functional material based on double laser melting forging according to claim 2, characterized in that, In Step 2, a forging time window is also set, and the existence time of the molten pool needs to be calculated according to the thermal physical properties of the material; 0.5 - 3 ms before the solidification of the molten pool, the forging timing is triggered, and the time interval Δt: 10 μs - 10 ms; a timing synchronization controller - a high-precision digital signal generator is configured.

7. The preparation method of the high-niobium alloy gradient functional material based on dual laser melting forging according to claim 2, characterized in that The specific content of Step 3 is: naturally cool the material processed in Step 2 to room temperature in the air, and then perform stress relief annealing treatment, the annealing temperature is 500 - 600 °C, and the holding time is 1 - 2 h.

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