Preparation method of high-temperature-creep-resistant nano-composite pressure vessel steel

Abstract

The preparation method of the high-temperature-creep-resistant nano-composite pressure vessel steel comprises the following steps that a lead sulfide precursor is dissolved in an organic solvent, and heating reaction is conducted under the inert gas condition to generate lead sulfide quantum dots; mixing quantum dots with amphiphilic molecules, and performing ultrasonic emulsification to form a quantum dot colloidal solution; mixing the quantum dot colloidal solution with supercritical carbon dioxide to form a homogeneous fluid phase; the steel matrix is placed in a high-pressure reaction kettle, the homogeneous fluid phase is introduced, permeation is conducted for 2-4 h under the conditions that the pressure is 10-15 MPa and the temperature is 50-70 DEG C, and a steel billet is obtained; the steel billet is placed in hot isostatic pressing equipment, heat preservation and pressure maintaining are conducted for 1-2 h in the inert gas environment under the conditions that the pressure ranges from 150 MPa to 200 MPa and the temperature ranges from 800 DEG C to 900 DEG C, and then the steel billet is cooled to the room temperature; semiconductor quantum dots are introduced into a metal matrix, atomic-scale interface strengthening is achieved through the quantum effect and the supercritical fluid permeation technology, and the steady-state creep rate of the material at the temperature of 600 DEG C can be reduced to 1 / 10 of that of a traditional process by combining the microcosmic strengthening advantage of the quantum dots and the macroscopic permeation advantage of supercritical fluid.

Description

Technical Field

[0001] This invention belongs to the field of alloy preparation technology, specifically referring to a method for preparing high-temperature creep-resistant nanocomposite pressure vessel steel. Background Technology

[0002] High-temperature creep resistance in pressure vessel steel refers to the slow plastic deformation caused by stress during long-term high-temperature service, which eventually leads to fracture failure. Traditional pressure vessel steels (such as low-alloy steel and austenitic stainless steel) have the following problems at high temperatures: 1. Grain boundary slip dominates: At high temperatures, the strength of grain boundaries decreases, dislocation movement intensifies, and grain boundary slip becomes the main mechanism of creep; 2. Carbide coarsening: Carbides precipitated in traditional heat treatment processes (such as M23C6) are prone to coarsening at high temperatures (size >100 nm), losing their pinning effect on dislocations; 3. Sensitivity to welding defects: Due to differences in thermophysical properties, welds in composite steel plates are prone to defects such as cracks and inclusions, becoming weak areas for creep fracture.

[0003] Traditional pressure vessel steel faces bottlenecks in high-temperature creep performance, such as grain boundary weakening and precipitate coarsening. While emerging technologies such as nanocomposite materials, additive manufacturing, and surface engineering have made breakthroughs, issues such as cost, process stability, and multi-scale synergistic optimization still need to be addressed. Summary of the Invention

[0004] In order to overcome some of the problems mentioned in the background above, the present invention provides a method for preparing high-temperature creep-resistant nanocomposite pressure vessel steel, so as to at least partially solve the above problems.

[0005] According to the technical solution of the present invention, a method for preparing high-temperature creep-resistant nanocomposite pressure vessel steel is provided, comprising the following steps: Lead sulfide precursors are dissolved in an organic solvent and heated under inert gas conditions to generate lead sulfide quantum dots. Quantum dots are mixed with amphiphilic molecules and then emulsified by ultrasound to form a colloidal solution of quantum dots; Quantum dot colloidal solution is mixed with supercritical carbon dioxide to form a homogeneous fluid phase; The steel matrix is ​​placed in a high-pressure reactor, and a homogeneous fluid phase is introduced. The mixture is then permeated for 2-4 hours at a pressure of 10-15 MPa and a temperature of 50-70℃ to obtain a steel billet. The steel billet is placed in a hot isostatic pressing apparatus and held under inert gas conditions at a pressure of 150-200 MPa and a temperature of 800-900℃ for 1-2 hours before being cooled to room temperature.

[0006] Furthermore, the lead sulfide precursor includes a sulfur source precursor and a lead source precursor, and the organic solvent includes oleylamine or octadecene. The sulfur source precursor includes one or more of sodium sulfide, hydrogen sulfide, thiourea, dialkyl dithiophosphate, and trioctylphosphine; The lead source precursor includes one or more of lead nitrate, lead acetate, lead chloride, and lead oleate.

[0007] Furthermore, the mixture is heated to 180-220℃ under inert gas conditions to generate lead sulfide quantum dots, and then cooled to 100-150℃ for annealing.

[0008] Furthermore, the steel matrix is ​​prepared by plasma-assisted sintering of raw materials, with the sintering temperature adjusted to 1100-1300℃ and the pressure to 50-100MPa.

[0009] Furthermore, it also includes surface treatment, in which the cooled steel billet is bombarded with low-temperature nitrogen plasma to remove residual organic matter and activate the interface.

[0010] Furthermore, the bombardment power of the low-temperature nitrogen plasma is 200-300W.

[0011] Furthermore, the steel billet after surface bombardment is annealed at 500-600℃ for 1-3 hours to induce the precipitation of nano-carbide around the quantum dots.

[0012] Furthermore, the amphiphilic molecule is selected as a distearate phosphatidylethanolamine-polyethylene glycol amphiphilic molecule, and the mass ratio of the amphiphilic molecule to the lead sulfide quantum dots is (10-20):1.

[0013] Furthermore, the present invention also provides a high-temperature creep-resistant nanocomposite pressure vessel steel, which is prepared according to the above preparation method.

[0014] Furthermore, the present invention also provides an application of high-temperature creep-resistant nanocomposite pressure vessel steel, which is prepared according to the above preparation method and applied in the field of pressure vessels.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention introduces semiconductor quantum dots into a metal matrix and utilizes quantum effects and supercritical fluid infiltration technology to achieve atomic-level interface strengthening. By combining the microscopic strengthening of quantum dots with the macroscopic infiltration advantages of supercritical fluids, the steady-state creep rate of the material at 700°C can be reduced to 1 / 10 of that of traditional processes. Detailed Implementation

[0016] The technical solutions in the embodiments will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection.

[0017] This invention provides a method for preparing high-temperature creep-resistant nanocomposite pressure vessel steel, comprising the following steps: Lead sulfide precursors are dissolved in organic solvents and heated under inert gas conditions to generate lead sulfide quantum dots. The size effect of quantum dots (such as quantum confinement effect) enables them to effectively pin dislocations at high temperatures. The surface-modified chains are compatible with supercritical fluids through their hydrophilic ends and adsorb quantum dots through their hydrophobic ends, thereby improving the permeation efficiency.

[0018] Quantum dots are mixed with amphiphilic molecules and emulsified by ultrasound to form a quantum dot colloidal solution; the quantum dot colloidal solution is then mixed with supercritical carbon dioxide to form a homogeneous fluid phase; A steel matrix is ​​placed in a high-pressure reactor, and a homogeneous fluid phase is introduced. The mixture is allowed to permeate for 2-4 hours at a pressure of 10-15 MPa and a temperature of 50-70℃ to obtain a steel billet. Supercritical CO2, with its low viscosity, high diffusivity, and strong dissolving ability, can carry quantum dots into the pores of the steel billet. Simultaneously, its near-liquid density ensures the uniform distribution of the quantum dots. The quantum dots embed themselves into the pore walls through physical adsorption and capillary action.

[0019] The steel billet is placed in a hot isostatic pressing equipment and held under inert gas at a pressure of 150-200 MPa and a temperature of 800-900℃ for 1-2 hours before being cooled to room temperature. Under high temperature and high pressure, quantum dots undergo interfacial diffusion reaction with the steel matrix. At the same time, the pores close to achieve densification, and the quantum dots are locked in the grain boundary or intragranular region, forming a "quantum dot-dislocation" interlocking structure, which significantly improves the creep resistance.

[0020] In a further embodiment of this example, the lead sulfide precursor includes a sulfur source precursor and a lead source precursor, and the organic solvent includes oleylamine or octadecene. The sulfur source precursor includes one or more of sodium sulfide, hydrogen sulfide, thiourea, dialkyl dithiophosphate, and trioctylphosphine; The lead source precursor includes one or more of lead nitrate, lead acetate, lead chloride, and lead oleate.

[0021] In a further embodiment of this example, lead sulfide quantum dots are generated by heating to 180-220°C under inert gas conditions, and then annealed at 100-150°C. The size of the lead sulfide quantum dots generated by heating and then annealing is controlled to be within the range of 3-5 nm. Quantum dots of 3-5 nm enhance dislocation pinning ability through quantum confinement effect; if the size is too large, the pinning efficiency decreases; if the size is too small, they are prone to aggregation, forming stress concentration points.

[0022] In a further embodiment of this invention, the steel matrix is ​​prepared by plasma-assisted sintering of raw materials, with the sintering temperature adjusted to 1100-1300℃ and the pressure to 50-100MPa. At 1100-1300℃, plasma activation forms a uniform microporous structure. Insufficient temperature leads to incomplete powder fusion, while excessive temperature may cause grain coarsening and reduce high-temperature stability. Sintering at 50-100 MPa can suppress pore collapse; too low pressure leads to uneven pore distribution, while too high pressure may prematurely close pores, hindering subsequent permeation. It should be noted that the porosity of the steel matrix is ​​15-20%, which ensures the mechanical strength of the matrix while providing quantum dot permeation channels.

[0023] In a further embodiment of this invention, a surface treatment is also included, in which the cooled steel billet is bombarded with low-temperature nitrogen plasma to remove residual organic matter and activate the interface.

[0024] In a further embodiment of this example, the bombardment power of the low-temperature nitrogen plasma is 200-300W. 200-300W nitrogen plasma removes surface organic matter and activates the interface; too low a power will result in incomplete cleaning, while too high a power will lead to the ablation of the surface nanolayer.

[0025] In a further embodiment of this invention, the steel billet after surface bombardment is annealed at 500-600°C for 1-3 hours to induce the precipitation of nano-carbides around the quantum dots. The temperature of 500-600°C is crucial for inducing the precipitation of nano-carbides along the quantum dots; too low a temperature will result in incomplete precipitation, while too high a temperature will cause the carbides to coarsen, reducing the strengthening effect.

[0026] In a further embodiment of this example, the amphiphilic molecule is selected as distearylphosphatidylethanolamine-polyethylene glycol (DSPE-PEG), and the mass ratio of the amphiphilic molecule to lead sulfide quantum dots is (10-20):1. DSPE-PEG is a block copolymer of distearylphosphatidylethanolamine (DSPE) and polyethylene glycol (PEG). Its hydrophobic end (DSPE) is adsorbed onto the surface of the quantum dots through van der Waals forces, while the hydrophilic end (PEG) forms a hydration layer to prevent quantum dot aggregation. When the mass ratio of DSPE-PEG is ≥5% (i.e., the mass ratio of lead sulfide quantum dots to the mass ratio of DSPE-PEG amphiphilic molecules), it can cover approximately 80% of the surface area of ​​the quantum dots, significantly improving colloidal stability. However, when it exceeds 10%, the quantum dots will be over-encapsulated, affecting their performance.

[0027] On the other hand, embodiments of the present invention also provide a high-temperature creep-resistant nanocomposite pressure vessel steel, which is prepared according to the above preparation method.

[0028] On the other hand, embodiments of the present invention also provide an application of high-temperature creep-resistant nanocomposite pressure vessel steel, which is applied in the field of pressure vessels.

[0029] Example 1:

[0030] Using Fe-Cr-Mo-W high-temperature alloy as raw material, porous steel was prepared by plasma-assisted sintering technology. The sintering temperature was adjusted to 1200℃ and the pressure to 80MPa, and the porosity of the steel matrix obtained was 18%.

[0031] Dialkyl dithiophosphate and lead nitrate were sequentially dissolved in oleylamine and heated to 200°C for complete reaction. The mixture was then cooled to 100°C for annealing to obtain lead sulfide quantum dots. Distearate phosphatidylethanolamine-polyethylene glycol amphiphilic molecules were mixed with quantum dots at a mass ratio of 10:1 and then ultrasonically emulsified to form a quantum dot colloidal solution.

[0032] A quantum dot colloidal solution was mixed with supercritical carbon dioxide to form a homogeneous fluid phase, wherein the mixing conditions were temperature > 31 °C and pressure > 7.4 MPa.

[0033] The steel matrix is ​​placed in a high-pressure reactor, and a homogeneous fluid phase is introduced. The mixture is permeated for 2 hours at a pressure of 10 MPa and a temperature of 50 °C to obtain a steel billet.

[0034] The steel billet is placed in a hot isostatic pressing apparatus and held at 150 MPa and 800℃ for 1 hour in an inert gas environment before being cooled to room temperature.

[0035] Example 2:

[0036] Using Fe-Cr-Mo-W high-temperature alloy as raw material, porous steel was prepared by plasma-assisted sintering technology. The sintering temperature was adjusted to 1200℃ and the pressure to 80MPa, and the porosity of the steel matrix obtained was 18%.

[0037] Dialkyl dithiophosphate and lead nitrate were sequentially dissolved in oleylamine and heated to 200°C for complete reaction. The mixture was then cooled to 100°C for annealing to obtain lead sulfide quantum dots. Distearate phosphatidylethanolamine-polyethylene glycol amphiphilic molecules were mixed with quantum dots at a mass ratio of 10:1 and then ultrasonically emulsified to form a quantum dot colloidal solution.

[0038] A quantum dot colloidal solution was mixed with supercritical carbon dioxide to form a homogeneous fluid phase, wherein the mixing conditions were temperature > 31 °C and pressure > 7.4 MPa.

[0039] The steel matrix is ​​placed in a high-pressure reactor, and a homogeneous fluid phase is introduced. The mixture is permeated for 2 hours at a pressure of 10 MPa and a temperature of 50 °C to obtain a steel billet.

[0040] The steel billet is placed in a hot isostatic pressing apparatus and held at 150 MPa and 800℃ for 1 hour in an inert gas environment before being cooled to room temperature.

[0041] Low-temperature nitrogen plasma with a power of 200W was used to bombard the material surface to remove residual organic matter and activate the interface. Then, the material was annealed at 500°C for 1 hour to induce the precipitation of nano-carbide around the quantum dots, forming a biphase reinforced structure.

[0042] Example 3:

[0043] Using Fe-Cr-Mo-W high-temperature alloy as raw material, porous steel was prepared by plasma-assisted sintering technology. The sintering temperature was adjusted to 1200℃ and the pressure to 80MPa, and the porosity of the steel matrix obtained was 18%.

[0044] Dialkyl dithiophosphate and lead nitrate were sequentially dissolved in oleylamine and heated to 200°C for complete reaction. The mixture was then cooled to 100°C for annealing to obtain lead sulfide quantum dots. Distearate phosphatidylethanolamine-polyethylene glycol amphiphilic molecules were mixed with quantum dots at a mass ratio of 10:1 and then ultrasonically emulsified to form a quantum dot colloidal solution.

[0045] A quantum dot colloidal solution was mixed with supercritical carbon dioxide to form a homogeneous fluid phase, wherein the mixing conditions were temperature > 31 °C and pressure > 7.4 MPa.

[0046] The steel matrix is ​​placed in a high-pressure reactor, and a homogeneous fluid phase is introduced. The mixture is permeated for 3 hours at a pressure of 10 MPa and a temperature of 50 °C to obtain a steel billet.

[0047] The steel billet is placed in a hot isostatic pressing apparatus and held at 150 MPa and 800℃ for 1 hour in an inert gas environment before being cooled to room temperature.

[0048] Low-temperature nitrogen plasma with a power of 200W was used to bombard the material surface to remove residual organic matter and activate the interface. Then, the material was annealed at 500°C for 1 hour to induce the precipitation of nano-carbide around the quantum dots, forming a biphase reinforced structure.

[0049] Example 4:

[0050] Using Fe-Cr-Mo-W high-temperature alloy as raw material, porous steel was prepared by plasma-assisted sintering technology. The sintering temperature was adjusted to 1200℃ and the pressure to 80MPa, and the porosity of the steel matrix obtained was 18%.

[0051] Dialkyl dithiophosphate and lead nitrate were sequentially dissolved in oleylamine and heated to 200°C for complete reaction. The mixture was then cooled to 100°C for annealing to obtain lead sulfide quantum dots. Distearate phosphatidylethanolamine-polyethylene glycol amphiphilic molecules were mixed with quantum dots at a mass ratio of 10:1 and then ultrasonically emulsified to form a quantum dot colloidal solution.

[0052] A quantum dot colloidal solution was mixed with supercritical carbon dioxide to form a homogeneous fluid phase, wherein the mixing conditions were temperature > 31 °C and pressure > 7.4 MPa.

[0053] The steel matrix is ​​placed in a high-pressure reactor, and a homogeneous fluid phase is introduced. The mixture is permeated for 4 hours at a pressure of 10 MPa and a temperature of 50 °C to obtain a steel billet.

[0054] The steel billet is placed in a hot isostatic pressing apparatus and held at 150 MPa and 800℃ for 1 hour in an inert gas environment before being cooled to room temperature.

[0055] Low-temperature nitrogen plasma with a power of 200W was used to bombard the material surface to remove residual organic matter and activate the interface. Then, the material was annealed at 500°C for 1 hour to induce the precipitation of nano-carbide around the quantum dots, forming a biphase reinforced structure.

[0056] Example 5:

[0057] Using Fe-Cr-Mo-W high-temperature alloy as raw material, porous steel was prepared by plasma-assisted sintering technology. The sintering temperature was adjusted to 1200℃ and the pressure to 80MPa, and the porosity of the steel matrix obtained was 18%.

[0058] Dialkyl dithiophosphate and lead nitrate were sequentially dissolved in oleylamine and heated to 200°C for complete reaction. The mixture was then cooled to 100°C for annealing to obtain lead sulfide quantum dots. Distearate phosphatidylethanolamine-polyethylene glycol amphiphilic molecules were mixed with quantum dots at a mass ratio of 15:1 and then ultrasonically emulsified to form a quantum dot colloidal solution.

[0059] A quantum dot colloidal solution was mixed with supercritical carbon dioxide to form a homogeneous fluid phase, wherein the mixing conditions were temperature > 31 °C and pressure > 7.4 MPa.

[0060] The steel matrix is ​​placed in a high-pressure reactor, and a homogeneous fluid phase is introduced. The mixture is permeated for 3 hours at a pressure of 10 MPa and a temperature of 50 °C to obtain a steel billet.

[0061] The steel billet is placed in a hot isostatic pressing apparatus and held at 150 MPa and 800℃ for 1 hour in an inert gas environment before being cooled to room temperature.

[0062] Low-temperature nitrogen plasma with a power of 200W was used to bombard the material surface to remove residual organic matter and activate the interface. Then, the material was annealed at 500°C for 1 hour to induce the precipitation of nano-carbide around the quantum dots, forming a biphase reinforced structure.

[0063] Example 6:

[0064] Using Fe-Cr-Mo-W high-temperature alloy as raw material, porous steel was prepared by plasma-assisted sintering technology. The sintering temperature was adjusted to 1200℃ and the pressure to 80MPa, and the porosity of the steel matrix obtained was 18%.

[0065] Dialkyl dithiophosphate and lead nitrate were sequentially dissolved in oleylamine and heated to 200°C for complete reaction. The mixture was then cooled to 100°C for annealing to obtain lead sulfide quantum dots. Distearate phosphatidylethanolamine-polyethylene glycol amphiphilic molecules were mixed with quantum dots at a mass ratio of 20:1 and then ultrasonically emulsified to form a quantum dot colloidal solution.

[0066] A quantum dot colloidal solution was mixed with supercritical carbon dioxide to form a homogeneous fluid phase, wherein the mixing conditions were temperature > 31 °C and pressure > 7.4 MPa.

[0067] The steel matrix is ​​placed in a high-pressure reactor, and a homogeneous fluid phase is introduced. The mixture is permeated for 3 hours at a pressure of 10 MPa and a temperature of 50 °C to obtain a steel billet.

[0068] The steel billet is placed in a hot isostatic pressing apparatus and held at 150 MPa and 800℃ for 1 hour in an inert gas environment before being cooled to room temperature.

[0069] Low-temperature nitrogen plasma with a power of 200W was used to bombard the material surface to remove residual organic matter and activate the interface. Then, the material was annealed at 500°C for 1 hour to induce the precipitation of nano-carbide around the quantum dots, forming a biphase reinforced structure.

[0070] Comparative Example 1 Using Fe-Cr-Mo-W high-temperature alloy as raw material, porous steel was prepared by plasma-assisted sintering technology. The sintering temperature was adjusted to 1200℃ and the pressure to 80MPa, and the porosity of the steel matrix obtained was 18%.

[0071] Dialkyl dithiophosphate and lead nitrate were dissolved sequentially in oleylamine and heated to 200°C to complete the reaction. The mixture was then cooled to 100°C for annealing to obtain lead sulfide quantum dots.

[0072] Lead sulfide quantum dots were mixed with supercritical carbon dioxide to form a homogeneous fluid phase, wherein the mixing conditions were temperature >31℃ and pressure >7.4 MPa.

[0073] The steel matrix is ​​placed in a high-pressure reactor, and a homogeneous fluid phase is introduced. The mixture is permeated for 3 hours at a pressure of 10 MPa and a temperature of 50 °C to obtain a steel billet.

[0074] The steel billet is placed in a hot isostatic pressing apparatus and held at 150 MPa and 800℃ for 1 hour in an inert gas environment before being cooled to room temperature.

[0075] Low-temperature nitrogen plasma with a power of 200W was used to bombard the material surface to remove residual organic matter and activate the interface. Then, the material was annealed at 500°C for 1 hour to induce the precipitation of nano-carbide around the quantum dots, forming a biphase reinforced structure.

[0076] Comparative Example 2 Using Fe-Cr-Mo-W high-temperature alloy as raw material, porous steel was prepared by plasma-assisted sintering technology. The sintering temperature was adjusted to 1200℃ and the pressure to 80MPa, and the porosity of the steel matrix obtained was 18%.

[0077] Dialkyl dithiophosphate and lead nitrate were sequentially dissolved in oleylamine and heated to 200°C for complete reaction. The mixture was then cooled to 100°C for annealing to obtain lead sulfide quantum dots. Distearate phosphatidylethanolamine-polyethylene glycol amphiphilic molecules were mixed with quantum dots at a mass ratio of 10:1 and then ultrasonically emulsified to form a quantum dot colloidal solution.

[0078] A quantum dot colloidal solution was mixed with supercritical carbon dioxide to form a homogeneous fluid phase, wherein the mixing conditions were temperature > 31 °C and pressure > 7.4 MPa.

[0079] The steel matrix is ​​placed in a high-pressure reactor, and a homogeneous fluid phase is introduced. The mixture is permeated for 6 hours at a pressure of 10 MPa and a temperature of 50 °C to obtain a steel billet.

[0080] The steel billet is placed in a hot isostatic pressing apparatus and held at 150 MPa and 800℃ for 1 hour in an inert gas environment before being cooled to room temperature.

[0081] Low-temperature nitrogen plasma with a power of 200W was used to bombard the material surface to remove residual organic matter and activate the interface. Then, the material was annealed at 500°C for 1 hour to induce the precipitation of nano-carbide around the quantum dots, forming a biphase reinforced structure.

[0082] Comparative Example 3 Using Fe-Cr-Mo-W high-temperature alloy as raw material, porous steel was prepared by plasma-assisted sintering technology. The sintering temperature was adjusted to 1200℃ and the pressure to 80MPa, and the porosity of the steel matrix obtained was 18%.

[0083] Dialkyl dithiophosphate and lead nitrate were sequentially dissolved in oleylamine and heated to 200°C for complete reaction. The mixture was then cooled to 100°C for annealing to obtain lead sulfide quantum dots. Distearate phosphatidylethanolamine-polyethylene glycol amphiphilic molecules were mixed with quantum dots at a mass ratio of 25:1 and then ultrasonically emulsified to form a quantum dot colloidal solution.

[0084] A quantum dot colloidal solution was mixed with supercritical carbon dioxide to form a homogeneous fluid phase, wherein the mixing conditions were temperature > 31 °C and pressure > 7.4 MPa.

[0085] The steel matrix is ​​placed in a high-pressure reactor, and a homogeneous fluid phase is introduced. The mixture is permeated for 3 hours at a pressure of 10 MPa and a temperature of 50 °C to obtain a steel billet.

[0086] The steel billet is placed in a hot isostatic pressing apparatus and held at 150 MPa and 800℃ for 1 hour in an inert gas environment before being cooled to room temperature.

[0087] Low-temperature nitrogen plasma with a power of 200W was used to bombard the material surface to remove residual organic matter and activate the interface. Then, the material was annealed at 500°C for 1 hour to induce the precipitation of nano-carbide around the quantum dots, forming a biphase reinforced structure.

[0088] The steels prepared in Examples 1-6 and Comparative Examples 1-3 were sampled and tested for their high-temperature creep resistance. The high-temperature creep resistance was evaluated by the high-temperature creep rupture time, and the standard was GB / T2039-2024. The test temperature was 700℃ and the test load was 2 / 3 of the material's room temperature yield strength ReL. The test results are shown in Table 1 below.

[0089] Table 1

[0090] As shown in Table 1 above, comparing Example 1 and Example 2, plasma treatment with high-energy particle bombardment to remove surface impurities can enhance the interfacial bonding strength between quantum dots and the matrix; aging heat treatment promotes the precipitation of the second phase, which, together with quantum dots, hinders dislocation movement at high temperatures, further improving the material's high-temperature creep resistance; comparing the results of Example 3 and Comparative Example 1, it can be seen that mixing quantum dots with amphiphilic molecules (such as DSPE-PEG) and then ultrasonically emulsifying to form a stable and dispersed quantum dot colloidal solution can effectively prevent aggregation and enhance compatibility with the metal matrix. The surface-modified PEG chains are compatible with supercritical fluids through their hydrophilic ends and adsorb quantum dots through their hydrophobic ends, improving penetration efficiency and effectively enhancing the material's high-temperature creep resistance; comparing the results of Example 3 and Comparative Example 2, it can be seen that the penetration time is 6 hours. This can lead to a thickening of the oxide layer on the substrate surface, resulting in poor bonding at the subsequent HIP interface, and thus affecting the material's high-temperature creep resistance. A comparison of the results of Example 5 and Comparative Example 3 shows that a low mass ratio of distearylphosphatidylethanolamine-polyethylene glycol amphiphilic molecules leads to insufficient surface coverage, resulting in poor colloidal stability and a tendency to precipitate or aggregate, thereby affecting the material's high-temperature creep resistance. A comparison of Examples 1-6 shows that Example 5 is the optimal example. Specifically, the steel obtained by placing the steel substrate in a high-pressure reactor with lead sulfide distearylphosphatidylethanolamine-polyethylene glycol amphiphilic molecules and quantum dots at a mass ratio of 15:1, introducing a homogeneous fluid phase, and permeating for 3 hours at a pressure of 10 MPa and a temperature of 50°C exhibits the best high-temperature creep resistance, and its yield strength and tensile strength also meet the requirements.

[0091] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a high-temperature creep-resistant nanocomposite pressure vessel steel, characterized in that, Includes the following steps: Lead sulfide precursors are dissolved in an organic solvent and heated under inert gas conditions to generate lead sulfide quantum dots. Quantum dots are mixed with amphiphilic molecules and then emulsified by ultrasound to form a colloidal solution of quantum dots; Quantum dot colloidal solution is mixed with supercritical carbon dioxide to form a homogeneous fluid phase; The steel matrix is ​​placed in a high-pressure reactor, and a homogeneous fluid phase is introduced. The mixture is then permeated for 2-4 hours at a pressure of 10-15 MPa and a temperature of 50-70℃ to obtain a steel billet. The steel billet is placed in a hot isostatic pressing apparatus and held under inert gas conditions at a pressure of 150-200 MPa and a temperature of 800-900℃ for 1-2 hours before being cooled to room temperature.

2. The method for preparing high-temperature creep-resistant nanocomposite pressure vessel steel according to claim 1, characterized in that, The lead sulfide precursor includes a sulfur source precursor and a lead source precursor, and the organic solvent includes oleylamine or octadecene. The sulfur source precursor includes one or more of sodium sulfide, hydrogen sulfide, thiourea, dialkyl dithiophosphate, and trioctylphosphine; The lead source precursor includes one or more of lead nitrate, lead acetate, lead chloride, and lead oleate.

3. The method for preparing high-temperature creep-resistant nanocomposite pressure vessel steel according to claim 2, characterized in that, Lead sulfide quantum dots are generated by heating to 180-220℃ under inert gas conditions, and then annealed at 100-150℃.

4. The method for preparing high-temperature creep-resistant nanocomposite pressure vessel steel according to claim 1, characterized in that, The steel matrix is ​​prepared by plasma-assisted sintering of raw materials, with the sintering temperature adjusted to 1100-1300℃ and the pressure to 50-100MPa.

5. The method for preparing high-temperature creep-resistant nanocomposite pressure vessel steel according to claim 1, characterized in that, It also includes surface treatment, in which the cooled steel billet is bombarded with low-temperature nitrogen plasma to remove residual organic matter and activate the interface.

6. The method for preparing high-temperature creep-resistant nanocomposite pressure vessel steel according to claim 5, characterized in that, The bombardment power of the low-temperature nitrogen plasma is 200-300W.

7. The method for preparing high-temperature creep-resistant nanocomposite pressure vessel steel according to any one of claims 5 or 6, characterized in that, The steel billet after surface bombardment is annealed at 500-600℃ for 1-3 hours to induce the precipitation of nano-carbide around the quantum dots.

8. The method for preparing high-temperature creep-resistant nanocomposite pressure vessel steel according to claim 1, characterized in that, The amphiphilic molecule is selected as distearate phosphatidylethanolamine-polyethylene glycol amphiphilic molecule, and the mass ratio of the amphiphilic molecule to lead sulfide quantum dots is (10-20):

1.

9. A high-temperature creep-resistant nanocomposite pressure vessel steel, characterized in that, The high-temperature creep-resistant nanocomposite pressure vessel steel prepared according to any one of claims 1-8.

10. An application of a high-temperature creep-resistant nanocomposite pressure vessel steel, characterized in that, Application of high-temperature creep-resistant nanocomposite pressure vessel steel prepared according to any one of claims 1-8 in the field of pressure vessels.

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