Heterogeneous material welding reliability characterization method applied to brush type sealing structure

Abstract

The invention relates to a nanoindentation and reliability characterization technology thereof, in particular to a heterogeneous material welding reliability characterization method applied to a brush type sealing structure. By means of the nanoindentation technology, mechanical properties such as hardness, elasticity modulus and plastic deformation of the welded joint are obtained by analyzing indenter deformation and indentation morphology. Meanwhile, indentation testing is carried out on different positions of the brush type sealing welding joint, and the performance comparison condition of all areas of the welding joint is obtained. Compared with a traditional reliability characterization means, the device and the method have the advantages that various areas of the heterogeneous welding joint including a base material, a heat affected zone and a fusion zone are tested under the nanoscale, various material performance indexes such as hardness, elasticity modulus and plastic deformation are measured at the same time, and the device and the method have high-precision and multifunctional testing capacity and are suitable for popularization and application. And moreover, the joint cannot be damaged or other properties cannot be influenced, and compared with a room-temperature stretching result, the nanoindentation technology has relatively high reliability and repeatability, and an accurate characterization result is obtained.

Description

Technical Field

[0001] This invention relates to nanoindentation and its reliability characterization technology, specifically a method for characterizing the welding reliability of heterogeneous materials in brush seal structures, applicable to the evaluation of welding quality of brush seal structures in turbomachinery such as aero engines, industrial gas turbines, and steam turbines. Background Technology

[0002] Sealing technology has always been a key technology in the development of high-performance aero engines. By reducing the leakage of airflow inside the engine, it can greatly improve the engine's performance and efficiency. Its characteristics have a significant impact on aero engine performance, especially the air passage seal, which directly affects the improvement of engine pressure ratio and turbine efficiency. As one of the key technologies in the development of modern advanced turbine machinery, brush seals have a leakage rate of 1 / 5 to 1 / 10 that of comb labyrinth seals, and can maintain a constant sealing capacity even under severe transient misalignment between moving and stationary components. This improves both unit efficiency and rotor stability, and has been applied to turbomachinery such as aero engines, industrial gas turbines, and steam turbines.

[0003] The brush seal structure consists of front and rear back plates and brush filaments sandwiched between them, all welded together. However, the brush filaments are prone to detachment and incomplete welds during welding and use, making the weld seam a weak point in the entire seal structure. Currently, tensile and impact tests are widely used to evaluate the reliability of welded joints. However, for brush seals, the weld size and base material condition significantly limit sampling and characterization for reliability evaluation. Therefore, this invention proposes a micro-area characterization method, nanoindentation technology. This method uses a nanoindenter to create tiny indentations in the material and measures its deformation and mechanical properties. By applying a micro-Newton level load to the sample surface, micro- and nano-level displacement responses are obtained. Data on the penetration depth as the load increases to the maximum force and then decreases is recorded, thus obtaining a load-displacement curve. Using mature mechanical models and calculation methods, the yield strength, strain hardening index, and other performance indicators of different micro-areas of the material are obtained. Furthermore, the constitutive equation and stress-strain curve of the material are derived to evaluate the reliability of the welded joint. This method is currently widely used in materials science for material design, manufacturing, and application.

[0004] Patent CN116460466A discloses a bonding and sealing composite welding method, welding system, and welding performance evaluation method, applied to rail vehicle body welding. It evaluates welding quality solely through airtightness testing, failing to reflect core mechanical indicators such as hardness and elastic modulus of the weld joint, and macroscopic testing cannot distinguish micro-area performance differences. Patent CN105562885A discloses a brush-type sealing welding method based on cobalt powder filling and 3D printing technology. It focuses solely on optimizing the welding process to solve welding uniformity and high-temperature resistance issues, judging welding quality only through dimensional measurements, lacking quantitative evaluation of mechanical properties. Patent CN102581486A discloses a brush-type sealing laser penetration spot welding method, only standardizing welding operation steps to improve welding efficiency and surface quality, unable to verify whether there are potential problems such as incomplete welds or detachment after welding. Patent CN103406677A discloses a dedicated brush ring welding machine, only optimizing the structure of the welding equipment to ensure welding operation accuracy, unable to reflect the mechanical performance state of the weld joint.

[0005] Therefore, it is necessary to develop a reliability characterization method specifically adapted to the welding characteristics of dissimilar materials for brush seals, to break through the limitations of traditional testing methods and ensure the reliability of brush seals under harsh working conditions. Summary of the Invention

[0006] To address the problem that the reliability of welding dissimilar materials in brush seals is difficult to accurately characterize in existing technologies, the purpose of this invention is to provide a method for characterizing the reliability of welding dissimilar materials in brush seal structures, enabling a comprehensive and accurate evaluation of the mechanical properties of each micro-zone of the welded joint, and providing a scientific basis for welding quality control.

[0007] The technical solution of this invention is:

[0008] A method for characterizing the welding reliability of heterogeneous materials applied to brush seal structures includes the following steps:

[0009] Step 1, Electron Beam Welding: A 2mm groove is cut inside the backplate using wire cutting technology. After grinding and polishing, cleaning with water, and cleaning with anhydrous ethanol and acetone, the groove is dried. The brush bristles are inserted longitudinally into the groove, and a vacuum electron beam welder is used for welding. The welding parameters are: accelerating voltage V=110kV, electron beam current A=12mA~14.5mA, and welding speed v=800mm / min.

[0010] Step 2, Nanoindentation Test: After the welded sample is ground and polished, the test is conducted on an Agilent G200 nanoindenter equipped with a Berkovich diamond indenter, using static load control mode, with a maximum load P. max=100mN, loading and unloading rate v=5mN / s, loading, holding and unloading time are all 20s, points are taken in the base material, heat-affected zone and fusion zone of the welded joint respectively, with no less than 5 points in each area, and the spacing between adjacent indentations is three times the indentation depth, to obtain load and indentation depth data.

[0011] Step 3: Constructing the stress-strain constitutive equation: During the nanoindentation test, the dynamic relationship between the load P applied by the diamond indenter and the indentation depth h is the Ph response. Based on the Ph response during the loading, holding, and unloading stages of the indentation, the loading curvature C is obtained by fitting the loading curve using Kick's Law, combined with the composite material modulus. The calculation results are used to extract the representative strain σ using the dimensionless function ∏1. 0.033 Fit the unloading curve, determine the slope S of the unloading curve at the maximum load, and solve for the strain hardening exponent n using the dimensionless function π²; then calculate the yield strength σ using the constitutive equation. y Stress-strain curves are obtained to characterize welding reliability.

[0012] In the method for characterizing the welding reliability of heterogeneous materials applied to brush-type sealing structures, in step one, the back plate material is AISI 410L ferritic stainless steel, and the brush bristle material is NS163 cobalt-based high-temperature alloy.

[0013] In the aforementioned method for characterizing the reliability of heterogeneous material welding applied to brush-type sealing structures, step two requires that the welding vacuum degree of the nanoindenter be no less than 10. -3 Pa.

[0014] In the aforementioned method for characterizing the welding reliability of heterogeneous materials applied to brush-type sealing structures, step three involves determining the composite material modulus. The elastic modulus E of the diamond indenter was calculated using the elastic modulus and Poisson's ratio of the indented material and the diamond indenter. i =1141 GPa, Poisson's ratio ν i =0.07.

[0015] In the method for characterizing the welding reliability of heterogeneous materials applied to brush-type sealing structures, in step three, when constructing the stress-strain constitutive equation, the material properties are considered, and the elastoplastic characteristics are accurately extracted from the Ph response through a dimensionless function.

[0016] In the aforementioned method for characterizing the welding reliability of heterogeneous materials applied to brush-type sealing structures, step three involves constructing the stress-strain constitutive equation as follows:

[0017] (a) Solving σ during the loading process 0.033

[0018] The Ph response of elastoplastic materials to sharp instrument indentations consists of three stages: loading, holding load, and unloading. The loading stage response is described by Kick's Law as Equation (1):

[0019] (1)

[0020] In the formula, C is the loading curvature, and the load P during the loading process is determined by the mechanical properties of the material itself and the indentation depth h, and is expressed as formula (2):

[0021] (2)

[0022] In the formula, σ 0.033 The stress used in the experiment is representative, and π1 is a dimensionless function. The modulus of the composite material is calculated using the elastic modulus and Poisson's ratio of the indenter material and the indenter material, as shown in equation (3):

[0023] (3)

[0024] In the formula, E is the elastic modulus of the indented material, ν is the Poisson's ratio of the indented material, and E i ν is the elastic modulus of the diamond indenter. i Let Poisson's ratio be the ratio of the diamond indenter. Combining equations (1) and (3), we have:

[0025] (4)

[0026] In the formula, σ 0.033 The stress used in the experiment is representative; ∏1 is a dimensionless function with the following specific form:

[0027] (5)

[0028] Based on formulas (1)-(5), σ is calculated. 0.033 ;

[0029] (b) Solving for the strain hardening exponent n during the unloading process

[0030] During the unloading process, the loaded load P satisfies equation (6):

[0031] (6)

[0032] In the formula, S is the slope of the unloading curve at the maximum load, which is determined by fitting the unloading curve under the maximum load, and h max is the maximum indentation depth of the indenter, and n is the hardening exponent; π², like π¹, is a dimensionless function, with the following specific form:

[0033] (7)

[0034] Solving formulas (6) and (7) yields the hardening index n;

[0035] (c) Solve for the yield strength σ using the constitutive equation. y

[0036] The elastoplastic behavior with true stress-strain relationship is represented by equation (8):

[0037] (8)

[0038] In the formula, σ is the true stress, ε is the true strain, R is the strength coefficient, and σ y ε y These are the initial yield strength and the corresponding yield strain, ε. p For plastic strain:

[0039] (9)

[0040] (10)

[0041] Combining equations (9) and (10), when the material enters the plastic strain stage, equation (8) becomes:

[0042] (11)

[0043] Where, σ 0.033 E and n are obtained through calculation, thus determining the yield strength σ. y Substituting into equation (8), we obtain the constitutive relation and stress-strain curve of the material.

[0044] The method for characterizing the welding reliability of heterogeneous materials applied to brush-type sealing structures verifies the reliability of the nanoindentation characterization results by comparing them with the results of room temperature tensile tests.

[0045] The design principle of this invention is:

[0046] Based on the relationship between the mechanical properties of materials and the deformation of the indenter, nanoindentation technology is used to analyze the deformation of the indenter and the morphology of the indentation. Micro-Newton-level loads are applied to the welded joint at the micro-nano scale to obtain micro-nano-level displacement responses, forming load-displacement curves. From these curves, mechanical indicators such as hardness, elastic modulus, plastic deformation, yield strength, and strain hardening index are obtained, and a stress-strain constitutive equation is constructed. When constructing the stress-strain constitutive equation, the inherent properties of the material are fully considered. A set of dimensionless functions is used to accurately extract the elastoplastic characteristics of the material from the Ph response of the indentation. The reliability of the characterization results is verified by comparing them with room temperature tensile results. Furthermore, by conducting differentiated point tests in the base material, heat-affected zone, and fusion zone, the performance comparison of each region is obtained, comprehensively reflecting the reliability status of the dissimilar material welded joint. Simultaneously, by performing indentation tests at different locations, the gradient performance distribution of the material is obtained.

[0047] Compared with traditional reliability characterization methods, the advantages and beneficial effects of this invention are as follows:

[0048] 1. High precision: Nanoindentation technology can be used for characterization at the nanoscale, and has high-precision measurement capabilities. It can measure the hardness, elastic modulus, plastic deformation and other performance indicators of materials. It can accurately distinguish the differences in mechanical properties between the base material, the heat-affected zone and the fusion zone, and effectively identify potential problems such as poor welding and poor fusion.

[0049] 2. Non-destructive: Nanoindentation technology is a non-destructive reliability characterization method. The testing process only produces micro- and nano-scale indentations, which will not damage the material or affect other properties. It does not affect the subsequent assembly and use of brush seals, and solves the problem that traditional destructive testing cannot be used for the characterization of finished products or key components.

[0050] 3. Multifunctional: Nanoindentation technology can simultaneously characterize multiple material properties, such as hardness, elastic modulus, and plastic deformation, and has multifunctional testing capabilities. By constructing stress-strain constitutive equations, it can achieve a comprehensive and quantitative evaluation of welding reliability.

[0051] 4. Flexibility: Nanoindentation technology is applicable to various materials, including metals, ceramics, and polymers, and has high flexibility.

[0052] 5. Reliability: Nanoindentation technology has high reliability and repeatability, and can obtain accurate and reliable characterization results, providing reliable data for the formulation of material performance standards. Attached Figure Description

[0053] Figure 1 This is a schematic diagram of the Ph curve of the elastoplastic material obtained by nanoindentation technology in this invention.

[0054] Figure 2 A schematic diagram of the elastoplastic stress-strain curve exhibited by the nanoindentation indentation material. Detailed Implementation

[0055] In its implementation, this invention utilizes nanoindentation technology to analyze the deformation of the indenter and the morphology of the indentation, thereby obtaining the mechanical properties of the welded joint, such as hardness, elastic modulus, and plastic deformation. Simultaneously, by performing indentation tests at different locations on the brush-sealed welded joint, the performance comparison of different regions of the welded joint is obtained. Compared to traditional reliability characterization methods, this invention can test various regions of heterogeneous welded joints, including the base material, heat-affected zone, and fusion zone, at the nanoscale. It can simultaneously measure multiple material properties such as hardness, elastic modulus, and plastic deformation, offering high precision and multifunctional testing capabilities without damaging the joint itself or affecting other properties. Most importantly, the characterization results have high reliability and repeatability, providing accurate and reliable test results.

[0056] To make the technical problems, technical solutions, and advantages of this invention clearer, a detailed description will be provided below in conjunction with specific embodiments. It should be noted that the descriptions of these embodiments are intended to aid in understanding the invention but do not constitute a limitation thereof. Unless otherwise specified, the experimental and detection methods described in the following embodiments are conventional methods; the reagents and materials described are commercially available unless otherwise specified.

[0057] This invention addresses the problems existing in current brush seal structure characterization techniques by proposing a method for characterizing the welding reliability of dissimilar materials in brush seal structures, comprising the following steps:

[0058] 1. Electron beam welding

[0059] A 2mm groove was cut inside the backplate using wire cutting technology. Oil, scale, and other impurities on the material surface were removed by grinding and polishing. The sample was then cleaned with water, followed by thorough cleaning with anhydrous ethanol and acetone to remove further impurities. Finally, the sample was dried with a hair dryer. During welding, the brush bristles were inserted longitudinally into the groove in the backplate. A high-energy electron beam was emitted from a vacuum electron beam welder to bombard the surface of the backplate. Under high energy density, the brush bristles and the backplate were melted through by the electron beam and welded together, achieving the welding objective. The specific welding parameters for electron beam welding were as follows: accelerating voltage V = 110kV, electron beam current A = 12mA~14.5mA, and welding speed v = 800mm / min.

[0060] 2. Nanoindentation test

[0061] After welding and polishing, the samples were subjected to nanoindentation tests on an Agilent G200 nanoindenter equipped with a Berkovich diamond indenter. The experiment was conducted in static load control mode, and the specific test parameters are as follows: maximum load setting P max =100mN, loading and unloading rate V=5mN / s, loading, holding and unloading time are all 20s, the total time for each nano-indentation is 60s, indentation points are taken in three regions of the weld joint: base material, heat-affected zone and fusion zone, with no less than 5 points in each region, and the distance between two adjacent indentations is three times the depth of a single indentation to reduce error, and a series of load and indentation depth data are obtained.

[0062] 3. Construct the stress-strain constitutive equations for the welded joint.

[0063] The Ph response of elastoplastic materials to sharp instrument indentations typically includes three stages: loading, holding load, and unloading. The representative strain σ is calculated based on the loading and unloading processes, respectively. 0.033 And the strain hardening exponent n, and then the yield strength σ is obtained by combining the constitutive equation. y The constitutive relation and stress-strain curve of the material are obtained to characterize the welding reliability. When constructing the stress-strain constitutive equation, the material properties are fully considered, and a set of dimensionless functions are used to accurately extract the elastoplastic properties of the material from the Ph response of the indentation.

[0064] 3.1 Solving σ during the loading process 0.033

[0065] like Figure 1 As shown, the Ph response of elastoplastic materials to sharp instrument indentations typically consists of three stages: loading, holding load, and unloading. Generally, Kick's Law can be used to describe the loading stage response as Equation (1):

[0066] (1)

[0067] In the formula, C is the loading curvature (mN / nm) 2 The load P (mN) during the loading process can be obtained by software fitting the curve of the loading stage. Based on the nature of the material, the load P (mN) during the loading process should be determined by the mechanical properties of the material itself, the indentation depth h (nm), etc., and can be expressed as equation (2):

[0068] (2)

[0069] In the formula, σ 0.033 The stress used in the experiment is the representative stress (MPa), and π1 is a dimensionless function. The composite material modulus (GPa) can be calculated using the elastic modulus and Poisson's ratio of the indenter material and the indenter material, as shown in equation (3):

[0070] (3)

[0071] In the formula, E is the elastic modulus (GPa) of the pressed-in material (brush seal heterogeneous material), and ν is the Poisson's ratio of the pressed-in material. i =1141 GPa and ν i =0.07 represents the elastic modulus and Poisson's ratio of the diamond indenter, respectively. Combining equations (1) and (3), we can obtain:

[0072] (4)

[0073] In the formula, σ 0.033 The representative stress used in the experiment (MPa, i.e., the stress with a strain of 0.033) fits the experimental data well within the error range. ∏1 is a dimensionless function, with the following specific form:

[0074] (5)

[0075] Based on formulas (1)-(5), σ can be calculated. 0.033 .

[0076] 3.2 Solving for the strain hardening exponent n during the unloading process

[0077] Similar to the loading process, during the unloading process, the loaded load P satisfies equation (6):

[0078] (6)

[0079] In the formula, S is the slope of the unloading curve at the maximum load (the derivative of the load with respect to the indentation depth), which can be determined by fitting the unloading curve under the maximum load, h max is the maximum indentation depth of the indenter (nm), and n is the hardening exponent; π², like π¹, is a dimensionless function, with the following specific form:

[0080] (7)

[0081] Therefore, by solving formulas (6) and (7), the hardening index n is obtained.

[0082] 3.3 Solving for the yield strength σ using the constitutive equation y

[0083] like Figure 2 As shown, the elastoplastic behavior with true stress-strain relationship is expressed by equation (8):

[0084] (8)

[0085] In the formula, σ is the true stress (MPa), ε is the true strain, R is the strength coefficient, and σ y ε y These represent the initial yield strength (MPa) and the corresponding yield strain, ε. p For plastic strain:

[0086] (9)

[0087] (10)

[0088] Combining equations (9) and (10), when the material enters the plastic strain stage, equation (8) becomes:

[0089] (11)

[0090] Where, σ 0.033 E and n are obtained through calculation, thus determining the yield strength σ. y (MPa). Substituting into equation (8), the constitutive relation and stress-strain curve of the material are obtained.

[0091] Following the steps of the above method, the following specific embodiments of the welded brush sealing structure are provided. By comparing with the room temperature tensile results, the nanoindentation characterization results have high reliability.

[0092] The equipment used in this invention is an EB4C-150-15-W electron beam welder with a power of 15KW, an accelerating voltage between 100kV and 160kV, a beam current between 0 and 100mA, and a welding vacuum degree of not less than 10. -3 Pa.

[0093] The backplate material used in this invention is an AISI 410L ferritic stainless steel plate with a diameter of 50mm × 20mm × 8mm, and the bristle material is NS163 cobalt-based high-temperature alloy wire with a diameter of 0.5mm. Both workpieces are in the rolled annealed state. The chemical composition of the backplate material and the bristle material is shown in Table 1.

[0094] Table 1. Chemical composition (mass percentage) of AISI 410L and NS163

[0095]

[0096] Example 1

[0097] The first step is to prepare a 50mm × 20mm × 8mm AISI 410L ferritic stainless steel plate and 0.5mm diameter NS163 cobalt-based superalloy bristles. Using a wire EDM machine, cut a 50mm × 15mm × 2mm groove 2mm from the top surface of the AISI 410L ferritic stainless steel plate to fill with the NS163 bristles. Insert the NS163 cobalt-based superalloy bristles into the groove on the back plate, ensuring a tight arrangement.

[0098] The second step involves grinding and polishing the sample to remove surface oil, oxide scale, and other impurities. The sample is then cleaned sequentially with water, anhydrous ethanol, and acetone, and subsequently dried. A vacuum electron beam welding experiment is conducted using welding parameters of A=12mA electron beam current, V=110kV accelerating voltage, and v=800mm / min welding speed. After welding, the vacuum atmosphere is maintained for 3-5 minutes, and then the electron beam vacuum chamber is opened to allow the weldment to air cool. The weldment is then removed, and its surface is wiped with alcohol.

[0099] The third step involves grinding and polishing the longitudinal section of the welded sample, followed by nanoindentation testing on an Agilent G200 nanoindenter equipped with a Berkovich diamond indenter. The experiment was conducted in static load control mode, with the specific test parameters being: maximum load P... max =100mN, loading and unloading rate V=5mN / s, holding time t=20s. Indentation points were taken in 6 areas, including the base material, heat-affected zone and fusion zone of the back plate and brush bristles. At least 5 points were taken in each area, and the distance between two adjacent indentations was three times the depth of a single indentation to reduce errors. A series of load and indentation depth data were obtained.

[0100] The fourth step is to obtain the loading curvature C by fitting the loading curve, and then combine it with the elastic modulus E of the diamond indenter. i =1141 GPa and Poisson's ratio ν i =0.07, calculate the modulus of the composite material. Representative strain σ is extracted using the dimensionless function ∏1. 0.033 Fit the unloading curve, determine the slope S of the unloading curve at the maximum load, and solve for the strain hardening exponent n using the dimensionless function π²; then calculate the yield strength σ using the constitutive equation. y Stress-strain constitutive equations were constructed. Using dimensionless functions, the yield strengths of the base material, heat-affected zone, and fusion zone of the backing plate and the base material, heat-affected zone, and fusion zone of the brush bristles were calculated to be 273.11 MPa, 395.94 MPa, and 400.88 MPa, and 1067.49 MPa, 750.15 MPa, and 367.06 MPa, respectively.

[0101] The fifth step is to conduct a room temperature tensile test on the backing material. The tensile results show that the yield strength of the material is 269.95 MPa, which is in good agreement with the strength results of the backing material obtained by nanoindentation.

[0102] Example 2

[0103] The first step is to prepare a 50mm × 20mm × 8mm AISI 410L ferritic stainless steel plate and 0.5mm diameter NS163 cobalt-based superalloy bristles. Using a wire EDM machine, cut a 50mm × 15mm × 2mm groove 2mm from the top surface of the AISI 410L ferritic stainless steel plate to fill with the NS163 bristles. Insert the NS163 cobalt-based superalloy bristles into the groove on the back plate, ensuring a tight arrangement.

[0104] The second step involves grinding and polishing the sample to remove surface oil, oxide scale, and other impurities. The sample is then cleaned sequentially with water, anhydrous ethanol, and acetone, and subsequently dried. A vacuum electron beam welding experiment is conducted using welding parameters of A=13.5mA electron beam current, V=110kV accelerating voltage, and v=800mm / min welding speed. After welding, the vacuum atmosphere is maintained for 3-5 minutes, and then the electron beam vacuum chamber is opened to allow the weldment to air cool. The weldment is then removed, and its surface is wiped with alcohol.

[0105] The third step involved grinding and polishing the longitudinal section of the welded sample, followed by nanoindentation testing on an Agilent G200 nanoindenter equipped with a Berkovich diamond indenter. The experiment was conducted in static load control mode, with the following parameters: maximum load Pmax = 100 mN, loading / unloading rate V = 5 mN / s, and holding time t = 20 s. Indentation points were taken in six areas: the base material of the backplate and brush bristles, the heat-affected zone, and the fusion zone. At least five points were taken in each area, ensuring that the distance between two adjacent indentations was three times the depth of a single indentation to minimize error. This yielded a series of load and indentation depth data.

[0106] The fourth step is to obtain the loading curvature C by fitting the loading curve, and then combine it with the elastic modulus E of the diamond indenter. i =1141 GPa and Poisson's ratio ν i =0.07, calculate the modulus of the composite material. Representative strain σ is extracted using the dimensionless function ∏1. 0.033 Fit the unloading curve, determine the slope S of the unloading curve at the maximum load, and solve for the strain hardening exponent n using the dimensionless function π²; then calculate the yield strength σ using the constitutive equation. yStress-strain constitutive equations were constructed. Using dimensionless functions, the yield strengths of the base material, heat-affected zone, and fusion zone of the backing plate and the base material, heat-affected zone, and fusion zone of the brush bristles were calculated to be 273.11 MPa, 364.84 MPa, and 772.18 MPa, and 1067.49 MPa, 530.0 MPa, and 760.66 MPa, respectively.

[0107] The fifth step is to conduct a room temperature tensile test on the backing material. The tensile results show that the yield strength of the backing is 269.95 MPa, which is in good agreement with the strength results of the backing base material obtained by nanoindentation.

[0108] Example 3

[0109] The first step is to prepare a 50mm × 20mm × 8mm AISI 410L ferritic stainless steel plate and 0.5mm diameter NS163 cobalt-based superalloy bristles. Using a wire EDM machine, cut a 50mm × 15mm × 2mm groove 2mm from the top surface of the AISI 410L ferritic stainless steel plate to fill with the NS163 bristles. Insert the NS163 cobalt-based superalloy bristles into the groove on the back plate, ensuring a tight arrangement.

[0110] The second step involves grinding and polishing the sample to remove surface oil, oxide scale, and other impurities. The sample is then cleaned sequentially with water, anhydrous ethanol, and acetone, and subsequently dried. A vacuum electron beam welding experiment is conducted using welding parameters of A=14.5mA electron beam current, V=110kV accelerating voltage, and v=800mm / min welding speed. After welding, the vacuum atmosphere is maintained for 3-5 minutes, and then the electron beam vacuum chamber is opened to allow the weldment to air cool. The weldment is then removed, and its surface is wiped with alcohol.

[0111] The third step involved grinding and polishing the longitudinal section of the welded sample, followed by nanoindentation testing on an Agilent G200 nanoindenter equipped with a Berkovich diamond indenter. The experiment was conducted in static load control mode, with the following parameters: maximum load Pmax = 100 mN, loading / unloading rate V = 5 mN / s, and holding time t = 20 s. Indentation points were taken in six areas: the base material of the backplate and brush bristles, the heat-affected zone, and the fusion zone. At least five points were taken in each area, ensuring that the distance between two adjacent indentations was three times the depth of a single indentation to minimize error. This yielded a series of load and indentation depth data.

[0112] The fourth step is to obtain the loading curvature C by fitting the loading curve, and then combine it with the elastic modulus E of the diamond indenter. i =1141 GPa and Poisson's ratio ν i =0.07, calculate the modulus of the composite material. Representative strain σ is extracted using the dimensionless function ∏1.0.033 Fit the unloading curve, determine the slope S of the unloading curve at the maximum load, and solve for the strain hardening exponent n using the dimensionless function π²; then calculate the yield strength σ using the constitutive equation. y Stress-strain constitutive equations were constructed. Using dimensionless functions, the yield strengths of the base material, heat-affected zone, and fusion zone of the backing plate and the base material, heat-affected zone, and fusion zone of the brush bristles were calculated to be 273.11 MPa, 372.21 MPa, and 780.73 MPa, and 1067.49 MPa, 674.12 MPa, and 804.65 MPa, respectively.

[0113] The fifth step is to conduct a room temperature tensile test on the backing material. The tensile results show that the yield strength of the material is 269.95 MPa, which is in good agreement with the strength results of the backing material obtained by nanoindentation.

[0114] The comparative analysis of the above embodiments shows that this invention utilizes nanoindentation technology to characterize the reliability of electron beam welding of dissimilar materials in brush-type sealing structures. The results indicate that welding parameters (electron beam current) have a significant impact on the strength of the welded joint. Room temperature tensile tests were conducted on the AISI 410L backplate, and the performance indicators obtained from nanoindentation were compared, confirming the accuracy of nanoindentation in characterizing the reliability of welded joints.

[0115] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for characterizing the welding reliability of dissimilar materials applied to brush-type sealing structures, characterized in that, Includes the following steps: Step 1, Electron Beam Welding: A 2mm groove is cut inside the backplate using wire cutting technology. After grinding and polishing, cleaning with water, and cleaning with anhydrous ethanol and acetone, the groove is dried. The brush bristles are inserted longitudinally into the groove, and a vacuum electron beam welder is used for welding. The welding parameters are: accelerating voltage V=110kV, electron beam current A=12mA~14.5mA, and welding speed v=800mm / min. Step 2, Nanoindentation Test: After the welded sample is ground and polished, the test is conducted on an Agilent G200 nanoindenter equipped with a Berkovich diamond indenter, using static load control mode, with a maximum load P. max =100mN, loading and unloading rate v=5mN / s, loading, holding and unloading time are all 20s, points are taken in the base material, heat-affected zone and fusion zone of the welded joint respectively, with no less than 5 points in each area, and the spacing between adjacent indentations is three times the indentation depth, to obtain load and indentation depth data. Step 3: Constructing the stress-strain constitutive equation: During the nanoindentation test, the dynamic relationship between the load P applied by the diamond indenter and the indentation depth h is the Ph response. Based on the Ph response during the loading, holding, and unloading stages of the indentation, the loading curvature C is obtained by fitting the loading curve using Kick's Law, combined with the composite material modulus. The calculation results are used to extract the representative strain σ using the dimensionless function ∏1. 0.033 Fit the unloading curve, determine the slope S of the unloading curve at the maximum load, and solve for the strain hardening exponent n using the dimensionless function π²; then calculate the yield strength σ using the constitutive equation. y Stress-strain curves are obtained to characterize welding reliability.

2. The method for characterizing the reliability of welding dissimilar materials applied to brush-type sealing structures according to claim 1, characterized in that, In step one, the backplate material is AISI 410L ferritic stainless steel, and the brush bristle material is NS163 cobalt-based high-temperature alloy.

3. The method for characterizing the reliability of welding dissimilar materials applied to brush-type sealing structures according to claim 1, characterized in that, In step two, the welding vacuum degree of the nanoindenter shall not be less than 10. -3 Pa.

4. The method for characterizing the reliability of welding dissimilar materials applied to brush-type sealing structures according to claim 1, characterized in that, In step three, the composite material modulus The elastic modulus E of the diamond indenter was calculated using the elastic modulus and Poisson's ratio of the indented material and the diamond indenter. i =1141 GPa, Poisson's ratio ν i =0.

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5. The method for characterizing the reliability of welding dissimilar materials applied to brush seal structures according to claim 1, characterized in that, In step three, when constructing the stress-strain constitutive equation, the material properties are considered, and the elastoplastic characteristics are accurately extracted from the Ph response using a dimensionless function.

6. The method for characterizing the welding reliability of dissimilar materials applied to brush seal structures according to claim 1, characterized in that, In step three, the stress-strain constitutive equations are constructed as follows: (a) Solving σ during the loading process 0.033 The Ph response of elastoplastic materials to sharp instrument indentations consists of three stages: loading, holding load, and unloading. The loading stage response is described by Kick's Law as Equation (1): （1） In the formula, C is the loading curvature, and the load P during the loading process is determined by the mechanical properties of the material itself and the indentation depth h, and is expressed as formula (2): （2） In the formula, σ 0.033 The stress used in the experiment is the representative stress, and π1 is a dimensionless function. The modulus of the composite material is calculated using the elastic modulus and Poisson's ratio of the indenter material and the indenter material, as shown in equation (3): （3） In the formula, E is the elastic modulus of the indented material, ν is the Poisson's ratio of the indented material, and E i ν is the elastic modulus of the diamond indenter. i Let Poisson's ratio be the ratio of the diamond indenter. Combining equations (1) and (3), we have: （4） In the formula, σ 0.033 The stress used in the experiment is representative; ∏1 is a dimensionless function with the following specific form: （5） Based on formulas (1)-(5), σ is calculated. 0.033 ; (b) Solving for the strain hardening exponent n during the unloading process During the unloading process, the loaded load P satisfies equation (6): （6） In the formula, S is the slope of the unloading curve at the maximum load, which is determined by fitting the unloading curve under the maximum load, and h max is the maximum indentation depth of the indenter, and n is the hardening exponent; π², like π¹, is a dimensionless function, with the following specific form: （7） Solving formulas (6) and (7) yields the hardening index n; (c) Solve for the yield strength σ using the constitutive equation. y The elastoplastic behavior with true stress-strain relationship is represented by equation (8): （8） In the formula, σ is the true stress, ε is the true strain, R is the strength coefficient, and σ y ε y These are the initial yield strength and the corresponding yield strain, ε. p For plastic strain: （9） （10） Combining equations (9) and (10), when the material enters the plastic strain stage, equation (8) becomes: （11） Where, σ 0.033 E and n are obtained through calculation, thus determining the yield strength σ. y Substituting into equation (8), we obtain the constitutive relation and stress-strain curve of the material.

7. The method for characterizing the reliability of welding dissimilar materials applied to brush-type sealing structures according to claim 1, characterized in that, The reliability of the nanoindentation characterization results was verified by comparing them with the results of room temperature tensile tests.

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