Metal material creep property test method and test piece

Abstract

The invention relates to the technical field of material performance testing, and discloses a metal material creep performance testing method and a test piece. The test piece is provided with a first uniform-section section, a second uniform-section section and a third uniform-section section of which the diameters are sequentially decreased, and high-temperature corrosion dynamic data of the metal material under multiple stress levels can be obtained at the same time by analyzing the high-temperature corrosion creep morphology of the three uniform-section sections with different diameters. Due to the fact that the first annular V-shaped groove, the second annular V-shaped groove and the third annular V-shaped groove which are different in configuration are formed in the fourth uniform-section section with the minimum section diameter, data support is provided for analyzing the interaction mechanism of high-temperature corrosion and creep loads by analyzing the high-temperature corrosion creep morphology of the three annular V-shaped grooves. By adopting the method for testing the creep property of the metal material, the influence of the machining precision, the material consistency, the test load and the environmental individual difference between the parallel pieces on the test result is reduced, the test efficiency is improved, and the test cost is saved.

Description

Technical Field

[0001] The present application relates to the technical field of material performance testing, and in particular to a creep performance testing method and test piece for a metal material. Background Art

[0002] In high-temperature service environments such as aircraft engines and gas turbines, metal materials (such as nickel-based superalloy GH4169, nickel-based single-crystal superalloy DD6, and titanium alloy Ti-6Al-4V) often experience performance degradation due to the coupled effects of high-temperature corrosion and creep, seriously impacting the lifespan and safety of the equipment. Especially in marine climates, mixed salts containing chloride ions (NaCl) and sulfate ions (Na2SO4) are easily deposited on the surfaces of engine hot-end components (such as turbine blades). These salts, reacting with high-temperature combustion gases, form a highly corrosive medium, accelerating material failure.

[0003] In the prior art, the high temperature corrosion-creep performance test of metal materials mainly adopts the following methods:

[0004] The group test method involves conducting tests on multiple sets of parallel specimens at different stress levels to obtain corrosion kinetics data and creep life. However, this method is limited by specimen processing accuracy, material batch differences, and fluctuations in the test environment, resulting in large data dispersion and difficulty in accurately characterizing the material's coupled corrosion-creep behavior.

[0005] Single configuration notch specimen testing: Research on notched specimens (such as film cooling holes and slot structures) requires the separate preparation of specimens with different configurations. This results in long test cycles and high costs, and it is impossible to compare the effect of the notch root radius (R parameter) on the corrosion-creep interaction on the same specimen.

[0006] Limitations of standardized testing standards: Existing standards (such as ASTM E139 and ISO 204) mainly focus on the evaluation of creep performance under single stress or uniform corrosion environment, and lack a systematic research method for the coupling of multiple stress gradients, localized corrosion and notch stress concentration.

[0007] Studies have shown that the coupling effect of high-temperature corrosion and creep is manifested as follows: the corrosive medium preferentially causes defects such as pits and grain boundary cracks in stress concentration areas such as notches, while the creep load further accelerates crack propagation, forming a vicious cycle of "corrosion-creep-crack".

[0008] It can be seen that the existing technology is difficult to achieve simultaneous testing of multiple stress levels in a single sample, and it is also impossible to quantitatively analyze the influence of notch configuration on corrosion-creep life. An efficient and accurate testing method is urgently needed to guide engineering design and material optimization. Summary of the Invention

[0009] The present invention provides a method and specimen for testing the creep properties of metal materials. This method can solve the technical problems in the prior art of high-temperature corrosion-creep properties testing of metal materials, such as low efficiency of simultaneous testing at multiple stress levels, difficulty in quantifying the influence of notch configuration gradients, and unclear coupling mechanisms between localized corrosion and stress concentration, caused by a large number of specimens, differences in material batches, and fluctuations in the test environment. The technical solution is as follows:

[0010] In one aspect, a method for testing creep properties of a metal material is provided, comprising the following steps:

[0011] Step 1: Processing a specimen, wherein both ends of the specimen are loading sections, and a first constant cross-section section, a second constant cross-section section, a third constant cross-section section, and a fourth constant cross-section section of equal length are sequentially arranged between the two loading sections, and the diameters of the first constant cross-section section, the second constant cross-section section, and the third constant cross-section section decrease in sequence, and the diameter of the fourth constant cross-section section is equal to the diameter of the third constant cross-section section. A first annular V-shaped groove, a second annular V-shaped groove, and a third annular V-shaped groove are evenly spaced on the fourth constant cross-section section, and the groove depths of the first annular V-shaped groove, the second annular V-shaped groove, and the third annular V-shaped groove are all equal, and the groove tip radiuses are all unequal;

[0012] Step 2: cleaning and drying the test piece, and then performing an initial quality inspection on the test piece;

[0013] Step 3: Prepare the corrosive medium salt solution;

[0014] Step 4: using the corrosive medium salt solution prepared in step 3, uniformly depositing the corrosive medium salt on the outer surfaces of the first uniform cross-sectional segment, the second uniform cross-sectional segment, and the third uniform cross-sectional segment, respectively, so that the corrosive medium salt deposited per unit area of each uniform cross-sectional segment is a preset deposition amount per unit area C0;

[0015] Step 5: Install the specimen in a creep testing machine, apply a constant preload to the specimen, heat it to the target temperature, and keep it warm;

[0016] Step 6: Apply creep load to the specimen at a constant rate to the target load and start the hot salt corrosion-creep coupled test;

[0017] Step 7: After the specimen breaks, turn off the high-temperature furnace of the creep testing machine, terminate the test, save the test data, wait for the specimen to cool down to room temperature, and then remove the specimen;

[0018] Step 8: Cut the specimen along its central axis and analyze the surface microstructures of the three equal-section sections and the microstructures of the three annular V-grooves. Combined with the corrosion kinetics data, the corrosion-creep coupling performance of the specimen is evaluated.

[0019] Furthermore, in step 3, the corrosive medium salt solution is a NaCl solution, a Na2SO4 solution, or a solution with a mixture of NaCl and Na2SO4 as a solute.

[0020] Furthermore, step 4 includes the following sub-steps:

[0021] Sub-step 4.1: Obtain the initial weight M0 of the specimen;

[0022] Sub-step 4.2: Calculate the surface area S1 of the first constant cross-sectional segment, the surface area S2 of the second constant cross-sectional segment, and the surface area S3 of the third constant cross-sectional segment based on the diameters of the three constant cross-sectional segments;

[0023] Sub-step 4.3: Deposit corrosive medium salt on the first, second, and third uniform cross-sectional segments, respectively, so that ΔM1 / S1=ΔM2 / S2=ΔM3 / S3=C0, where ΔM1, ΔM2, and ΔM3 are the mass increments of the first, second, and third uniform cross-sectional segments after the deposition of the corrosive medium salt.

[0024] Furthermore, in step 4, atomization method is used to deposit corrosive medium salt on the outer surfaces of the first uniform cross-sectional segment, the second uniform cross-sectional segment and the third uniform cross-sectional segment.

[0025] Furthermore, in step 2, performing an initial quality inspection on the test piece includes:

[0026] Conduct diameter accuracy testing on each section of equal cross section, and the machining diameter of each section of equal cross section shall not exceed ±4% of the design diameter of each section of equal cross section;

[0027] The radius of the groove tip of each annular V-shaped groove was tested, and the error between the processed groove tip radius and the designed groove tip radius of each annular V-shaped groove was ±0.015mm.

[0028] Furthermore, in step 1, the diameters of the first, second and third uniform cross-section segments are D1 = 12-14 mm, D2 = 9-11 mm and D3 = 6-8 mm, respectively;

[0029] The groove depths of the first annular V-groove, the second annular V-groove, and the third annular V-groove are all H=0.8-1.2 mm; the groove tip radius of the first annular V-groove is R1=0.65-0.85 mm, the groove tip radius of the second annular V-groove is R2=0.15-0.35 mm, and the groove tip radius of the third annular V-groove is R3=0.05-0.25 mm;

[0030] In step 4, C0 = 3 ± 0.5 mg / cm 2 ;

[0031] In step 5, the constant preload size is 50N to 200N, the target temperature is 650℃-950℃, and the holding time is half an hour;

[0032] In step 6, the creep load is applied at a speed of 50 N / s, and the target load range is 10000 N-14000 N.

[0033] Furthermore, step 8 includes the following sub-steps:

[0034] Sub-step 8.1: Select a first observation position on the first uniform cross-sectional segment, select a second observation position on the second uniform cross-sectional segment, and select a third observation position on the third uniform cross-sectional segment;

[0035] Sub-step 8.2: Record and analyze the first observation position, the second observation position, and the third observation position using an optical instrument, and analyze the types of corrosion products at the first observation position, the second observation position, and the third observation position using a chemical analysis device;

[0036] Sub-step 8.3: Study the effect of stress level on the high-temperature corrosion-creep failure behavior of metallic materials;

[0037] Sub-step 8.4: Selecting a fourth observation position at the root of the first annular V-shaped groove, selecting a fifth observation position at the root of the second annular V-shaped groove, and selecting a sixth observation position at the root of the third annular V-shaped groove;

[0038] Sub-step 8.5: Record and analyze the corrosion products at the fourth, fifth, and sixth observation locations using an optical instrument, and analyze the corrosion products at the fourth, fifth, and sixth observation locations using a chemical analysis device.

[0039] Sub-step 8.6: Study the effect of the slot tip radius on the high-temperature corrosion-creep failure behavior of metallic materials.

[0040] Furthermore, in sub-step 8.2, optical instruments are used to record and analyze the first observation position, the second observation position, and the third observation position, respectively, including: counting the corrosion pits at the first observation position, the second observation position, and the third observation position, and measuring the depth of each corrosion pit, respectively, and drawing a corrosion pit depth and number distribution table for the first equal-section segment, a corrosion pit depth and number distribution table for the second equal-section segment, and a corrosion pit depth and number distribution table for the third equal-section segment, respectively.

[0041] Furthermore, in sub-step 8.5, optical instruments are used to record and analyze the fourth observation position, the fifth observation position, and the sixth observation position, respectively, including: counting the corrosion pits at the fourth observation position, the fifth observation position, and the sixth observation position and measuring the depth of each corrosion pit, respectively, and drawing a corrosion pit depth and number distribution table at the root of the first annular V-shaped groove, a corrosion pit depth and number distribution table at the root of the second annular V-shaped groove, and a corrosion pit depth and number distribution table at the root of the third annular V-shaped groove, respectively.

[0042] Compared with the prior art, the technical solution provided by the embodiment of the present application of a method for testing creep properties of metal materials has the following beneficial effects:

[0043] On the one hand, since the specimen is provided with a first, second and third equal-section sections with decreasing diameters, after the target load is applied to the specimen, the creep load of each equal-section section is equal to the quotient of the target load and the cross-sectional area. Then, the creep stress of the first, second and third equal-section sections increases in sequence. By analyzing the high-temperature corrosion creep morphology of the three equal-section sections with different diameters, the high-temperature corrosion dynamics data of the metal material under multiple stress levels can be obtained simultaneously. On the other hand, since the first, second and third annular V-grooves with three different configurations are provided on the fourth equal-section section with the same diameter as the third equal-section section, the high-temperature corrosion creep morphology of the three different configurations of the annular V-grooves provides data support for analyzing the interaction mechanism between high-temperature corrosion and creep load. At the same time, the test method of the present application can also measure the high-temperature corrosion-creep life of the notch configuration with the weakest stress concentration on the fourth cross-section section with the smallest diameter, reducing the number of parallel parts used and shortening the test cycle. The metal material creep performance testing method of the present application reduces the impact of individual differences in processing accuracy, material consistency, test load and environment between parallel parts on the test results, improves test efficiency and saves test costs.

[0044] In the second aspect, the present application also provides a test piece for the creep performance of metal materials, which is applied to the above-mentioned metal material creep performance testing method, and the test piece includes: two loading sections; a first equal cross-section section, a second equal cross-section section, a third equal cross-section section and a fourth equal cross-section section, which are equal in length and connected in sequence and are arranged between the two loading sections, and the diameters of the first equal cross-section section, the second equal cross-section section and the third equal cross-section section decrease in sequence, and the diameter of the fourth equal cross-section section is equal to the diameter of the third equal cross-section section. The fourth equal cross-section section is provided with a first annular V-shaped groove, a second annular V-shaped groove and a third annular V-shaped groove at equal intervals, and the groove depths of the first annular V-shaped groove, the second annular V-shaped groove and the third annular V-shaped groove are equal, and the groove tip radii are different.

[0045] The beneficial effects of the embodiments of the test specimens of the present application include at least: a test specimen is provided with a first, second, and third uniform cross-sectional segments of successively decreasing diameters, and a fourth uniform cross-sectional segment having the same diameter as the third cross-sectional segment is provided with a first annular V-groove, a second annular V-groove, and a third annular V-groove of three different configurations. Using such a test specimen for high-temperature corrosion-creep testing of metal materials reduces the number of parallel components used, shortens the test cycle, and reduces the impact of individual differences in machining accuracy, material consistency, test load, and environment on the test results between parallel components, thereby improving test efficiency and saving test costs.

[0046] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0048] Figure 1 This is a flow chart of a method for testing creep properties of metal materials provided in an embodiment of the present application;

[0049] Figure 2 It is a schematic structural diagram of the test piece provided in the embodiment of the present application;

[0050] Figure 3 yes Figure 2 A partial enlarged view of point A in the middle;

[0051] Figure 4 is the surface corrosion pit morphology at the first observation position on the first uniform cross-section segment;

[0052] Figure 5 The morphology of the corrosion pit in the longitudinal section at the first observation position on the first uniform cross-section segment;

[0053] Figure 6 The surface corrosion pit morphology at the second observation position on the second equal cross-section segment;

[0054] Figure 7 is the corrosion pit morphology of the longitudinal section at the second observation position on the second equal cross-section segment;

[0055] Figure 8 The surface corrosion pit morphology at the third observation position on the third equal cross-section segment;

[0056] Figure 9 The morphology of the corrosion pit in the longitudinal section at the third observation position on the third equal-section segment;

[0057] Figure 10 The table below shows the distribution of corrosion pit depth and number in the first uniform cross-section segment.

[0058] Figure 11 The table below shows the distribution of corrosion pit depth and number in the second uniform cross-section segment.

[0059] Figure 12 This is the distribution table of corrosion pit depth and number in the third equal cross-section segment;

[0060] Figure 13 This is a table showing the depth and number distribution of corrosion pits at the root of the first annular V-groove;

[0061] Figure 14 This is a table showing the depth and number distribution of corrosion pits at the root of the second annular V-groove;

[0062] Figure 15 This is a table showing the distribution of corrosion pit depth and number at the root of the third annular V-groove.

[0063] Description of Reference Numerals

[0064] 1-loading section; 2-first uniform cross-section section; 3-second uniform cross-section section; 4-third uniform cross-section section; 5-fourth uniform cross-section section; 5-first annular V-shaped groove; 6-second annular V-shaped groove; 7-third annular V-shaped groove. DETAILED DESCRIPTION

[0065] The following describes the specific embodiments of the present disclosure in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure and are not intended to limit the present disclosure.

[0066] In this disclosure, unless otherwise indicated, directional terms such as "upper" and "lower" generally refer to the relative positions of the corresponding components in the direction of gravity when in use. "Inside" and "outside" refer to the relative positions of the corresponding components themselves. Furthermore, the terms "first" and "second" used in this disclosure are intended to distinguish one element from another and do not convey sequential or significant meanings. In the following description, when referring to the drawings, unless otherwise indicated, identical reference numerals in different drawings indicate identical or similar elements.

[0067] In a first aspect, a method for testing creep properties of a metal material comprises the following steps:

[0068] Step 1: Processing a specimen, wherein both ends of the specimen are loading sections, and a first constant cross-section section, a second constant cross-section section, a third constant cross-section section, and a fourth constant cross-section section of equal length are sequentially arranged between the two loading sections, and the diameters of the first constant cross-section section, the second constant cross-section section, and the third constant cross-section section decrease in sequence, and the diameter of the fourth constant cross-section section is equal to the diameter of the third constant cross-section section. A first annular V-shaped groove, a second annular V-shaped groove, and a third annular V-shaped groove are evenly spaced on the fourth constant cross-section section, and the groove depths of the first annular V-shaped groove, the second annular V-shaped groove, and the third annular V-shaped groove are all equal, and the groove tip radiuses are all unequal;

[0069] Step 2: cleaning and drying the test piece, and then performing an initial quality inspection on the test piece;

[0070] Step 3: Prepare the corrosive medium salt solution;

[0071] Step 4: using the corrosive medium salt solution prepared in step 3, uniformly depositing the corrosive medium salt on the outer surfaces of the first uniform cross-sectional segment, the second uniform cross-sectional segment, and the third uniform cross-sectional segment, respectively, so that the corrosive medium salt deposited per unit area of each uniform cross-sectional segment is a preset deposition amount per unit area C0;

[0072] Step 5: Install the specimen in a creep testing machine, apply a constant preload to the specimen, heat it to the target temperature, and keep it warm;

[0073] Step 6: Apply creep load to the specimen at a constant rate to the target load and start the hot salt corrosion-creep coupled test;

[0074] Step 7: After the specimen breaks, turn off the high-temperature furnace of the creep testing machine, terminate the test, save the test data, wait for the specimen to cool down to room temperature, and then remove the specimen;

[0075] Step 8: Cut the specimen along its central axis and analyze the surface microstructures of the three equal-section sections and the microstructures of the three annular V-grooves. Combined with the corrosion kinetics data, the corrosion-creep coupling performance of the specimen is evaluated.

[0076] In the above method, on the one hand, since the specimen is provided with a first, second and third equal cross-sectional sections with decreasing diameters, after the target load is applied to the specimen, the creep load of each equal cross-sectional section is equal to the quotient of the target load and the cross-sectional area, then the creep stress of the first, second and third equal cross-sectional sections increases in sequence. By analyzing the high-temperature corrosion creep deformation morphology of the three equal cross-sectional sections with different diameters, the high-temperature corrosion dynamics data of the metal material under multiple stress levels can be obtained simultaneously. On the other hand, since three different configurations of the first annular V-groove, the second annular V-groove and the third annular V-groove are provided on the fourth equal cross-sectional section with the same diameter as the third equal cross-sectional section, by analyzing the high-temperature corrosion creep deformation morphology of the three different configurations of the annular V-groove, data support is provided for analyzing the interaction mechanism between high-temperature corrosion and creep load. At the same time, the test method of the present application can also measure the high-temperature corrosion-creep life of the notch configuration with the weakest stress concentration on the fourth cross-sectional section with the smallest diameter, thereby reducing the number of parallel parts used and shortening the test cycle. The metal material creep performance testing method of the present application reduces the impact of individual differences in processing accuracy, material consistency, test load and environment between parallel parts on the test results, improves test efficiency and saves test costs.

[0077] Furthermore, in step 3, the corrosive medium salt solution is a NaCl solution, a Na2SO4 solution, or a solution containing a mixture of NaCl and Na2SO4 as a solute. The concentration of the corrosive medium salt solution can be set according to specific test requirements. According to an embodiment of the present application, the solute of the corrosive medium salt solution includes a mixed salt of 5% by mass of NaCl and 95% by mass of Na2SO4, and the mixed salt is used to prepare a mixed salt solution with a concentration of 0.025g / ml.

[0078] In order to ensure that the corrosion salt deposited per unit area of the first, second and third equal cross-sectional sections of the specimen is equal, step 4 may further include the following sub-steps:

[0079] Sub-step 4.1: Obtain the initial weight m0 of the specimen;

[0080] Sub-step 4.2: Calculate the surface area S1 of the first constant cross-sectional segment, the surface area S2 of the second constant cross-sectional segment, and the surface area S3 of the third constant cross-sectional segment based on the diameters of the three constant cross-sectional segments;

[0081] Sub-step 4.3: Deposit corrosive medium salt on the first, second, and third uniform cross-sectional segments, respectively, so that ΔM1 / S1=ΔM2 / S2=ΔM3 / S3=C0, where ΔM1, ΔM2, and ΔM3 are the mass increments of the first, second, and third uniform cross-sectional segments after the deposition of the corrosive medium salt.

[0082] Furthermore, in step 4, atomization method is used to deposit corrosive medium salt on the outer surfaces of the first uniform cross-sectional segment, the second uniform cross-sectional segment and the third uniform cross-sectional segment.

[0083] Furthermore, in step 2, performing an initial quality inspection on the test piece includes:

[0084] Conduct diameter accuracy testing on each section of equal cross section, and the machining diameter of each section of equal cross section shall not exceed ±4% of the design diameter of each section of equal cross section;

[0085] The radius of the groove tip of each annular V-shaped groove was tested, and the error between the processed groove tip radius and the designed groove tip radius of each annular V-shaped groove was ±0.015mm.

[0086] Furthermore, in step 1, the diameters of the first uniform cross-section segment, the second uniform cross-section segment, and the third uniform cross-section segment are D1 = 12-14 mm, D2 = 9-11 mm, and D3 = 6-8 mm, respectively; the groove depths of the first annular V-shaped groove, the second annular V-shaped groove, and the third annular V-shaped groove are all 0.8-1.2 mm; the groove tip radius of the first annular V-shaped groove is R1 = 0.65-0.85 mm, the groove tip radius of the second annular V-shaped groove is R2 = 0.15-0.35 mm, and the groove tip radius of the third annular V-shaped groove is R3 = 0.05-0.25 mm; in step 4, C0 = 3 ± 0.5 mg / cm 2 ; In step 5, the constant preload size is 50N~200N, the target temperature is 650℃-950℃, and the holding time is half an hour; in step 6, the creep load is loaded at a speed of 50N / s, and the target load range is 10000N-14000N.

[0087] Furthermore, step 8 includes the following sub-steps:

[0088] Sub-step 8.1: Select a first observation position on the first uniform cross-sectional segment, select a second observation position on the second uniform cross-sectional segment, and select a third observation position on the third uniform cross-sectional segment;

[0089] Sub-step 8.2: Record and analyze the first observation position, the second observation position, and the third observation position using an optical instrument, and analyze the types of corrosion products at the first observation position, the second observation position, and the third observation position using a chemical analysis device;

[0090] Sub-step 8.3: Study the effect of stress level on the high-temperature corrosion-creep failure behavior of metallic materials;

[0091] Sub-step 8.4: Selecting a fourth observation position at the root of the first annular V-shaped groove, selecting a fifth observation position at the root of the second annular V-shaped groove, and selecting a sixth observation position at the root of the third annular V-shaped groove;

[0092] Sub-step 8.5: Record and analyze the corrosion products at the fourth, fifth, and sixth observation locations using an optical instrument, and analyze the corrosion products at the fourth, fifth, and sixth observation locations using a chemical analysis device.

[0093] Sub-step 8.6: Study the effect of the slot tip radius on the high-temperature corrosion-creep failure behavior of metallic materials.

[0094] Furthermore, in sub-step 8.2, optical instruments are used to record and analyze the first observation position, the second observation position, and the third observation position, respectively, including: counting the corrosion pits at the first observation position, the second observation position, and the third observation position, and measuring the depth of each corrosion pit, respectively, and drawing a corrosion pit depth and number distribution table for the first equal-section segment, a corrosion pit depth and number distribution table for the second equal-section segment, and a corrosion pit depth and number distribution table for the third equal-section segment, respectively.

[0095] Furthermore, in sub-step 8.5, optical instruments are used to record and analyze the fourth observation position, the fifth observation position, and the sixth observation position, respectively, including: counting the corrosion pits at the fourth observation position, the fifth observation position, and the sixth observation position and measuring the depth of each corrosion pit, respectively, and drawing a corrosion pit depth and number distribution table at the root of the first annular V-shaped groove, a corrosion pit depth and number distribution table at the root of the second annular V-shaped groove, and a corrosion pit depth and number distribution table at the root of the third annular V-shaped groove, respectively.

[0096] The following describes the contents involved in the above embodiment in conjunction with an optional embodiment.

[0097] Step 1: Processing the specimen, selecting a GH-4169 alloy round rod as the test material, processing the two ends of the GH-4169 alloy round rod into loading sections, and processing the first, second, third, and fourth equal-section sections with a length of L = 20 mm along the axial direction between the two loading sections. The diameters of the first, second, and third equal-section sections are D1 = 13, D2 = 10, D3 = 7, and D4 = 7, respectively; the first, second, and third annular V-grooves with a groove depth H of 1 mm are processed at equal intervals on the fourth equal-section section, and the groove tip radius of the first, second, and third annular V-grooves are R1 = 0.75, R2 = 0.25, and R3 = 0.13, respectively;

[0098] Step 2: Clean the specimen. Use clean water and anhydrous ethanol ultrasonic cleaning to clean the surface of the specimen. Use a hair dryer to keep the surface dry and clean.

[0099] Step 3: Use a mixed salt of 5% by mass of NaCl and 95% by mass of Na2SO4 as solutes, and prepare a mixed salt solution with a concentration of 0.025g / ml as a corrosive medium salt solution.

[0100] Step 4: Deposit the corrosive medium salt

[0101] Sub-step 4.1: Measure the initial mass of the specimen using an electronic balance, denoted as M0;

[0102] Sub-step 4.2: Calculate the surface area S1 of the first uniform cross-sectional segment, the surface area S2 of the first uniform cross-sectional segment, and the surface area S3 of the third uniform cross-sectional segment according to S=πDL;

[0103] Sub-step 4.3: Calculate the weight of corrosion salt that needs to be deposited on the first uniform cross-section segment ΔM 1＝ C0S1. Calculate the weight of corrosion salt ΔM that needs to be deposited in the second section of equal cross section 2＝ C0 S2, calculate the weight of corrosion salt that needs to be deposited in the third equal cross-section section ΔM 3＝ C0S3;

[0104] Sub-step 4.4: Preheat the specimen to 150°C in a heating furnace, then use an atomizer filled with salt solution to spray salt mist onto the first uniform cross-sectional section of the specimen, so that the specimen has a weight increase of ΔM1 after the corrosion salt is uniformly deposited on the first uniform cross-sectional section;

[0105] Sub-step 4.5: Spray salt spray on the second uniform cross-section of the specimen so that the specimen has a weight increase of ΔM2 after the corrosion salt is uniformly deposited on the second uniform cross-section;

[0106] Sub-step 4.6: Spray salt mist on the third section of the specimen so that the specimen evenly deposits corrosion salt on the third section of the specimen and the weight gain is ΔM3;

[0107] Step 5: Install the specimen on the RD-100 electronic creep endurance tester and apply a constant pre-tensile load of 200N to the specimen. Then, turn on the high-temperature furnace, set the target temperature to 650℃, and start heating. During the heating process, the specimen is always subjected to a tensile load of 200N.

[0108] Step 6: When the actual temperature reaches the target temperature of 650°C, keep it at this temperature for 30 minutes, and then apply a creep load at a rate of 50N / s, with a target load of 13737.5N.

[0109] According to the stress calculation formula: σ = F / A, where σ represents stress, F represents the force acting on the object, and A represents the area over which the force acts. It can be found that under this load level, the creep stress of the first uniform cross-section segment is approximately 103.56 MPa, the creep stress of the second uniform cross-section segment is approximately 175 MPa, the creep stress of the third uniform cross-section segment is approximately 260 MPa-364 MPa, and the nominal creep stress at the root of all notches in the fourth uniform cross-section segment is 357.14 MPa.

[0110] Step 7: After the specimen fractures, turn off the high-temperature furnace, terminate the test, and save the test data. When the specimen cools down to room temperature, remove the specimen. During this process, pay attention to protecting the specimen fracture morphology.

[0111] Step 8: Analyze and summarize the conclusions

[0112] Sub-step 8.1: Cut the specimen along its central axis, select a first observation position on a first uniform cross-sectional segment of the specimen, select a second observation position on a second uniform cross-sectional segment of the specimen, and select a third observation position on a third uniform cross-sectional segment of the specimen;

[0113] Substep 8.2: Reference Figures 4 to 9 , Figure 4 is the surface corrosion pit morphology at the first observation position on the first equal cross-section segment, Figure 5 The morphology of the corrosion pit in the longitudinal section at the first observation position on the first uniform cross-section segment; Figure 6 is the surface corrosion pit morphology at the second observation position on the second equal cross-section segment, Figure 7 is the corrosion pit morphology of the longitudinal section at the second observation position on the second equal cross-section segment; Figure 8 The surface corrosion pit morphology at the third observation position on the third equal cross-section segment is shown in Figure 1. Figure 9 The morphology of the corrosion pit in the longitudinal section at the third observation position on the third equal-section segment; Figure 4 、 Figure 6 and Figure 8 Used to count the number of corrosion pits, Figure 5 、 Figure 7 and Figure 9 Used to observe the depth of corrosion pits.

[0114] Substep 8.3: Reference Figures 10 to 12 As shown, the depth and number of corrosion pits of the above three equal-section segments were statistically analyzed, and a distribution table of the corrosion pit depth and number of the first equal-section segment, a distribution table of the corrosion pit depth and number of the second equal-section segment, and a distribution table of the corrosion pit depth and number of the third equal-section segment were drawn.

[0115] from Figures 4 to 12 It can be seen that under the action of high-temperature corrosion-creep coupling, pits and microcracks are generated on the surface of the specimen, and the higher the creep stress level, the larger the pit size and the lower the density of the alloy surface.

[0116] The results show that the higher the creep stress level, the greater the overall corrosion pit depth, indicating more severe high-temperature corrosion. Combining the surface and cross-sectional micromorphology and the pit depth distribution results, it is concluded that high-temperature corrosion and creep loading promote each other.

[0117] Sub-step 8.4: Selecting a fourth observation position at the root of the first annular V-shaped groove, selecting a fifth observation position at the root of the second annular V-shaped groove, and selecting a sixth observation position at the root of the third annular V-shaped groove;

[0118] Sub-step 8.5: Using an optical instrument to record and analyze the fourth observation position, the fifth observation position, and the sixth observation position;

[0119] Substep 8.6: Reference Figures 13 to 15 As shown, the corrosion pit depth and number distribution table of the first annular V-shaped groove root, the corrosion pit depth and number distribution table of the second annular V-shaped groove root, and the corrosion pit depth and number distribution table of the third annular V-shaped groove root are drawn respectively.

[0120] from Figures 13 to 15 It can be seen that the smaller the groove tip radius, the greater the overall pit depth. Since the smaller the radius, the stronger the notch stress concentration effect, the following conclusion can be drawn: the greater the stress concentration factor, the higher the stress level near the root of the annular V-shaped groove, and the more obvious the effect of promoting hot corrosion. Therefore, on the fourth section, the smaller the groove tip radius, the greater the pit depth.

[0121] In the second aspect, the embodiment of the present application also provides a test piece for the creep performance of metal materials, including: two loading sections 11, a first uniform cross-section section 2, a second uniform cross-section section 3, a third uniform cross-section section 4 and a fourth uniform cross-section section 5 arranged between the two loading sections 1, and the diameters of the first uniform cross-section section 2, the second uniform cross-section section 3 and the third uniform cross-section section 4 decrease in sequence, the diameter of the fourth uniform cross-section section 5 is equal to the diameter of the third uniform cross-section section 4, and the fourth uniform cross-section section 5 is evenly spaced and provided with a first annular V-shaped groove 5, a second annular V-shaped groove 6 and a third annular V-shaped groove 7, the groove depths of the first annular V-shaped groove 5, the second annular V-shaped groove 6 and the third annular V-shaped groove 7 are all equal, and the groove tip radius is all unequal. In order to avoid stress concentration due to diameter difference, the first uniform cross-section section 2, the second uniform cross-section section 3 and the third uniform cross-section section 4 are rounded, the first uniform cross-section section 2 and a loading section 1 are rounded, and the fourth uniform cross-section section 5 and another loading section 1 are rounded.

[0122] In the above embodiment, a specimen is provided with a first uniform cross-sectional segment 2, a second uniform cross-sectional segment 3, and a third uniform cross-sectional segment 4, each of decreasing diameters. Furthermore, a fourth uniform cross-sectional segment 5, which has the same diameter as the third uniform cross-sectional segment 4, is provided with three differently configured first annular V-grooves 5, second annular V-grooves 6, and third annular V-grooves 7. Using such specimens for high-temperature corrosion-creep testing of metallic materials reduces the number of parallel specimens used, shortens the test cycle, and mitigates the impact of individual differences in machining accuracy, material consistency, test load, and environmental conditions on the test results, thereby improving test efficiency and saving test costs.

[0123] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings. However, the present disclosure is not limited to the specific details of the above embodiments. Within the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the scope of protection of the present disclosure.

[0124] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0125] In addition, the various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A method for testing creep properties of metal materials, characterized in that: The following steps are involved: Step 1: Processing a specimen, wherein both ends of the specimen are loading sections, and a first constant cross-section section, a second constant cross-section section, a third constant cross-section section, and a fourth constant cross-section section of equal length are sequentially arranged between the two loading sections, and the diameters of the first constant cross-section section, the second constant cross-section section, and the third constant cross-section section decrease in sequence, and the diameter of the fourth constant cross-section section is equal to the diameter of the third constant cross-section section. A first annular V-shaped groove, a second annular V-shaped groove, and a third annular V-shaped groove are evenly spaced on the fourth constant cross-section section, and the groove depths of the first annular V-shaped groove, the second annular V-shaped groove, and the third annular V-shaped groove are all equal, and the groove tip radiuses are all unequal; Step 2: cleaning and drying the test piece, and then performing an initial quality inspection on the test piece; Step 3: Prepare the corrosive medium salt solution; Step 4: using the corrosive medium salt solution prepared in step 3, uniformly depositing the corrosive medium salt on the outer surfaces of the first uniform cross-sectional segment, the second uniform cross-sectional segment, and the third uniform cross-sectional segment, respectively, so that the corrosive medium salt deposited per unit area of each uniform cross-sectional segment is a preset deposition amount per unit area C0; Step 5: Install the specimen in a creep testing machine, apply a constant preload to the specimen, heat it to the target temperature, and keep it warm; Step 6: Apply creep load to the specimen at a constant speed to the target load and start the hot salt corrosion-creep coupled test; Step 7: After the specimen breaks, turn off the high-temperature furnace of the creep testing machine, terminate the test, save the test data, wait for the specimen to cool down to room temperature, and then remove the specimen; Step 8: Cut the specimen along its central axis and analyze the surface microstructures of the three equal-section sections and the microstructures of the three annular V-grooves. Combined with the corrosion kinetics data, the corrosion-creep coupling performance of the specimen is evaluated.

2. The method for testing creep properties of metal materials according to claim 1, characterized in that: In step 3, the corrosive medium salt solution is a NaCl solution, a Na2SO4 solution, or a solution with a mixture of NaCl and Na2SO4 as a solute.

3. The method for testing creep properties of metal materials according to claim 1, wherein: Step 4 includes the following sub-steps: Sub-step 4.1: Obtain the initial weight M0 of the specimen; Sub-step 4.2: Calculate the surface area S1 of the first constant cross-sectional segment, the surface area S2 of the second constant cross-sectional segment, and the surface area S3 of the third constant cross-sectional segment based on the diameters of the three constant cross-sectional segments; Sub-step 4.3: Deposit corrosive medium salt on the first, second, and third uniform cross-sectional segments, respectively, so that ΔM1 / S1=ΔM2 / S2=ΔM3 / S3=C0, where ΔM1, ΔM2, and ΔM3 are the mass increments of the first, second, and third uniform cross-sectional segments after the deposition of the corrosive medium salt.

4. The method for testing creep properties of metal materials according to claim 1, wherein: In the step 4, atomization is used to deposit corrosive medium salt on the outer surfaces of the first uniform cross-sectional segment, the second uniform cross-sectional segment, and the third uniform cross-sectional segment.

5. The method for testing creep properties of metal materials according to claim 1, wherein: In step 2, performing initial quality inspection on the test piece includes: Conduct diameter accuracy testing on each section of equal cross section, and the machining diameter of each section of equal cross section shall not exceed ±4% of the design diameter of each section of equal cross section; The radius of the groove tip of each annular V-shaped groove was tested, and the error between the processed groove tip radius and the designed groove tip radius of each annular V-shaped groove was ±0.015mm.

6. The method for testing creep properties of metal materials according to claim 1, wherein: In step 1, the diameters of the first, second and third uniform cross-section segments are D1 = 12-14 mm, D2 = 9-11 mm and D3 = 6-8 mm, respectively; The groove depths of the first annular V-groove, the second annular V-groove, and the third annular V-groove are all H=0.8-1.2 mm; the groove tip radius of the first annular V-groove is R1=0.65-0.85 mm, the groove tip radius of the second annular V-groove is R2=0.15-0.35 mm, and the groove tip radius of the third annular V-groove is R3=0.05-0.25 mm; In step 4, C0 = 3 ± 0.5 mg / cm 2 ; In step 5, the constant preload size is 50N to 200N, the target temperature is 650℃-950℃, and the holding time is half an hour; In step 6, the creep load is applied at a speed of 50 N / s, and the target load range is 10000 N-14000 N.

7. The method for testing creep properties of metal materials according to claim 1, wherein: Step 8 contains the following sub-steps: Sub-step 8.1: Select a first observation position on the first uniform cross-sectional segment, select a second observation position on the second uniform cross-sectional segment, and select a third observation position on the third uniform cross-sectional segment; Sub-step 8.2: Record and analyze the first observation position, the second observation position, and the third observation position using an optical instrument, and analyze the types of corrosion products at the first observation position, the second observation position, and the third observation position using a chemical analysis device; Sub-step 8.3: Study the effect of stress level on the high-temperature corrosion-creep failure behavior of metallic materials; Sub-step 8.4: Selecting a fourth observation position at the root of the first annular V-shaped groove, selecting a fifth observation position at the root of the second annular V-shaped groove, and selecting a sixth observation position at the root of the third annular V-shaped groove; Sub-step 8.5: Record and analyze the corrosion products at the fourth, fifth, and sixth observation locations using an optical instrument, and analyze the corrosion products at the fourth, fifth, and sixth observation locations using a chemical analysis device. Sub-step 8.6: Study the effect of the slot tip radius on the high-temperature corrosion-creep failure behavior of metallic materials.

8. The method for testing creep properties of metal materials according to claim 7, characterized in that: In sub-step 8.2, optical instruments are used to record and analyze the first observation position, the second observation position, and the third observation position, respectively, including: counting the corrosion pits at the first observation position, the second observation position, and the third observation position and measuring the depth of each corrosion pit, respectively, and drawing a corrosion pit depth and number distribution table for the first equal-section segment, a corrosion pit depth and number distribution table for the second equal-section segment, and a corrosion pit depth and number distribution table for the third equal-section segment, respectively.

9. The method for testing creep properties of metal materials according to claim 7, characterized in that: In sub-step 8.5, optical instruments are used to record and analyze the fourth observation position, the fifth observation position, and the sixth observation position, respectively, including: counting the corrosion pits at the fourth observation position, the fifth observation position, and the sixth observation position and measuring the depth of each corrosion pit, respectively, and drawing a corrosion pit depth and number distribution table for the root of the first annular V-shaped groove, a corrosion pit depth and number distribution table for the root of the second annular V-shaped groove, and a corrosion pit depth and number distribution table for the root of the third annular V-shaped groove, respectively.

10. A test piece for testing creep properties of metal materials, applied to the creep properties testing method of metal materials according to any one of claims 1 to 9, characterized in that: The test piece includes: Two loading segments (1); A first uniform cross-section section (2), a second uniform cross-section section (3), a third uniform cross-section section (4) and a fourth uniform cross-section section (5) are arranged between two loading sections (1), are of equal length and are connected in sequence, and the diameters of the first uniform cross-section section (2), the second uniform cross-section section (3) and the third uniform cross-section section (4) decrease in sequence, the diameter of the fourth uniform cross-section section (5) is equal to the diameter of the third uniform cross-section section (4), and a first annular V-shaped groove (5), a second annular V-shaped groove (6) and a third annular V-shaped groove (7) are arranged at equal intervals on the fourth uniform cross-section section (5), the groove depths of the first annular V-shaped groove (5), the second annular V-shaped groove (6) and the third annular V-shaped groove (7) are all equal, and the groove tip radiuses are all unequal.

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