CN116275011B - Powder for additive manufacturing, ultra-high strength and toughness steel, and preparation method and application thereof - Google Patents
Powder for additive manufacturing, ultra-high strength and toughness steel, and preparation method and application thereof Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/09—Mixtures of metallic powders
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
- B22F10/20—Direct sintering or melting
- B22F10/28—Powder bed fusion, e.g. selective laser melting [SLM] or electron beam melting [EBM]
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F5/00—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product
- B22F5/007—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product of moulds
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y10/00—Processes of additive manufacturing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y70/00—Materials specially adapted for additive manufacturing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y80/00—Products made by additive manufacturing
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/52—Ferrous alloys, e.g. steel alloys containing chromium with nickel with cobalt
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/25—Process efficiency
Abstract
The application relates to the technical field of ultra-high strength and toughness steel, in particular to powder for additive manufacturing, ultra-high strength and toughness steel, and a preparation method and application thereof. The additive manufacturing powder includes an 18Ni alloy powder and an aeromet 100 alloy powder. The ultra-high strength and toughness steel prepared by the additive manufacturing powder provided by the application has high yield strength and fracture toughness.
Description
Technical Field
The application relates to the technical field of ultra-high strength and toughness steel, in particular to powder for additive manufacturing, ultra-high strength and toughness steel, and a preparation method and application thereof.
Background
The ultra-high strength and toughness steel has high strength and high fracture toughness, and is an indispensable key material for tip manufacturing industries such as aerospace, ocean engineering and the like. Additive manufacturing is an important technological means for realizing low-cost and high-degree-of-freedom forming of complex components of ultra-high-strength and high-toughness steel. Therefore, developing ultra-high strength and toughness steel suitable for additive manufacturing is an urgent need for upgrading of pushing equipment.
The microstructure of most conventional ultra-high strength and toughness steels is martensitic, a precipitated phase, and a small amount (typically less than 5% by volume) of austenite. In the ultra-high strength and toughness steel, excellent fracture toughness of the material is ensured by various means such as improving the nickel content of a martensitic matrix (nickel is an important toughening element), introducing a fine dispersed precipitated phase, forming a small amount of austenite with toughening effect and the like. However, when preparing an additive manufactured ultra-high strength and toughness steel part, the additive manufacturing process inevitably introduces metallurgical defects such as holes, inclusions and the like in the material, and the defects may significantly reduce the fracture toughness of the material, so that the industrial application of the material is severely restricted.
Disclosure of Invention
Based on this, it is necessary to provide a powder for additive manufacturing having a higher yield strength and fracture toughness, an ultra-high strength and toughness steel, and a preparation method and application thereof. Therefore, microstructure different from that of the traditional ultra-high-strength and tough steel is obtained in the process of manufacturing the ultra-high-strength and tough steel by additive, so that the microstructure has more excellent intrinsic toughness, and adverse effects of metallurgical defects on the comprehensive mechanical properties of the material for manufacturing the additive are overcome.
In a first aspect, the present application provides a powder for additive manufacturing comprising an 18Ni alloy powder and an aero met100 alloy powder.
In some embodiments, the 18Ni alloy powder is 20% -80% by mass of the additive manufacturing powder, with the balance being aeromet 100 alloy powder.
In some embodiments, the 18Ni alloy powder is 60% -80% in content, and the balance is AerMet100 alloy powder.
In some embodiments, the particle size of the 18Ni alloy powder and the aeromet 100 alloy powder are each independently 15-53 μm.
In a second aspect, the application also provides a method for preparing the ultra-high strength and toughness steel, which comprises the following steps:
preparing a premix powder comprising an 18Ni alloy powder and an aeromet 100 alloy powder;
forming the premixed powder into a steel billet by adopting a selective laser melting technology; and
and heat treatment is carried out on the steel billet by adopting a direct aging process or a deep cooling aging process.
In some embodiments, the direct aging process comprises the steps of: placing the steel billet at 450-500 ℃ for heat preservation for 3-10 hours, and cooling to room temperature;
the cryogenic aging process comprises the following steps: firstly, preserving the temperature of the steel billet below-77 ℃ for 0.5-5 h; then heating to room temperature; and then heating to 450-500 ℃, preserving heat for 3-10 hours, and cooling to room temperature.
In some embodiments, the process parameters of the selective laser melting technique include:
the layering thickness is 15-35 mu m, the scanning line distance is 80-120 mu m, the laser power is 150-250W, and the scanning speed is 700 mm/s-1500 mm/s.
In some embodiments, the method employed to prepare the pre-mix powder is dry blending.
In a third aspect, the present application further provides an ultra-high strength and toughness steel produced by the production method according to the second aspect.
In some embodiments, the ultra-high strength and toughness steel has a yield strength of 1600 MPa or more and a fracture toughness of 70 MPa-m or more 1/2 。
In a fourth aspect, the application also provides an application of the ultra-high strength and toughness steel in manufacturing mechanical parts or forming dies.
The application takes 18Ni alloy powder and AerMet100 alloy powder as raw materials to prepare the ultra-high strength and toughness steel with high yield strength, high fracture toughness and low alloy cost. The ultra-high strength and toughness steel of the application takes martensite as a matrix, and elements such as Ni, ti, cr, mo, C and the like in the matrix can form Ni 3 (Ti, mo), fe-Mo intermetallic compound, M 2 C alloy carbideWherein M is mainly Mo and Cr, and the like, thereby playing the role of improving the strength and fracture toughness of the matrix. The ultra-high strength and toughness steel provided by the application can form a submicron-scale cellular structure and a fine martensitic transformation in the selective laser melting (Selective Laser Melting, SLM) process. Under the induction of Ti and Mo segregation at the cell structure wall (hereinafter referred to as "cell wall"), the steel can generate obvious austenite reverse transformation in the subsequent heat treatment, and the volume fraction of the reverse transformation austenite can reach more than 15 percent, which is far superior to the traditional ultra-high-strength and tough steel. On one hand, the shape of the part of reverse transformed austenite is similar to that of cell walls, the thickness is less than 100 a nm a, the reverse transformed austenite has obvious fine grain strengthening effect, and the yield strength is obviously higher than that of common micron-sized/submicron-sized austenite; on the other hand, under the coordination of elements such as Ni, co, mo, cr, ti, C, the mechanical stability of the reverse transformed austenite is moderate, and the reverse transformed austenite can not only generate plastic deformation, but also generate deformation under a certain stress level to induce martensitic transformation (Deformation Induced Martensite Transformation, DIMT) to be transformed into new martensite which contains a small amount of carbon elements and is relatively hard, thereby contributing to additional work hardening. In conclusion, the ultra-high-strength and high-toughness steel prepared by the method has a microstructure (comprising a plurality of precipitation strengthening phases such as intermetallic compounds and carbides and a large amount of cellular reverse transformation austenite) which is remarkably different from that of the conventional ultra-high-toughness steel, and has excellent yield strength and higher fracture toughness than that of the ultra-high-strength and high-toughness steel manufactured by additive material subjected to conventional heat treatment.
In addition, the application adopts an in-situ alloying technical route, namely: the premixed powder prepared from the two kinds of powder is used as an additive manufacturing raw material, and the two kinds of powder are fused in situ in the additive manufacturing process to obtain a billet with a component between the two kinds of powder, and the powder with a target component is not directly smelted to be used as the additive manufacturing raw material. On one hand, the technical route can avoid carbide liquation caused by coexistence of Ti and C in a melt in the smelting process, and prevent coarse carbide which damages the material performance from being formed; on the other hand, the components of the target steel can be customized by regulating and controlling the proportion of the alloy powder on the basis of ensuring compact molding, thereby meeting the diversified mechanical property requirements in different application scenes. The preparation process provided by the application does not need solid solution and quenching treatment, and can simplify the process, reduce energy consumption and avoid size distortion caused by quenching.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present application, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is a scanning electron microscope image of the ultra-high strength and toughness steel (before heat treatment) prepared in example 1;
FIG. 2 is a transmission electron microscope image of the ultra-high strength and toughness steel (after heat treatment) prepared in example 1;
FIG. 3 is a scanning electron microscope image of the ultra-high strength and toughness steel (after heat treatment) obtained in example 1.
Detailed Description
In order that the application may be readily understood, a more complete description of the application will be rendered by reference to the appended drawings. Preferred embodiments of the present application are shown in the drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.
The term "room temperature" is also referred to as normal temperature or general temperature. In the present application, room temperature is defined as 18 ℃ to 35 ℃.
Using additive manufacturingDefects such as inclusions and holes cannot be avoided when ultrahigh-strength steel is prepared, and meanwhile, the prepared material has too large original austenite and martensite variant sizes. If the materials are treated by the traditional heat treatment system, the toughness of the ultra-high-strength and tough steel is obviously deteriorated by the characteristics, so that a large gap exists between the toughness and the toughness of the ultra-high-strength and tough steel prepared by the traditional process (smelting-casting-forging), and the requirements of practical application cannot be met. Therefore, the application provides the ultra-high strength and toughness steel suitable for additive manufacturing process, which has higher yield strength (more than 2 GPa) and fracture toughness (more than 70 MPa m) 1/2 Above) and is low in cost.
In a first aspect, the present application provides a powder for additive manufacturing comprising an 18Ni alloy powder and an aero met100 alloy powder.
The application takes 18Ni alloy powder and AerMet100 alloy powder as raw materials to prepare the ultra-high strength and toughness steel with high yield strength, high fracture toughness and low alloy cost. The ultra-high strength and toughness steel of the application takes martensite as a matrix, and elements such as Ni, ti, cr, mo, C and the like in the matrix can form Ni 3 (Ti, mo), fe-Mo intermetallic compound, M 2 The C alloy carbide (M is mainly Mo, cr) and other fine dispersed precipitated phases, thereby playing the role of improving the strength and fracture toughness of the matrix. The ultra-high strength and toughness steel provided by the application can form a submicron-scale cellular structure and a fine martensitic transformation in the selective laser melting (Selective Laser Melting, SLM) process. Under the induction of segregation of Ti and Mo at the cell wall, the steel can generate obvious austenite reverse transformation in the subsequent heat treatment, and the volume fraction of the reverse transformation austenite can reach more than 15 percent, which is far superior to the traditional ultra-high-strength and tough steel. On one hand, the shape of the part of reverse transformed austenite is similar to that of cell walls, the thickness is less than 100 a nm a, the reverse transformed austenite has obvious fine grain strengthening effect, and the yield strength is obviously higher than that of common micron-sized/submicron-sized austenite; on the other hand, under the coordination of Ni, co, mo, cr, ti, C and other elements, the mechanical stability of the reverse transformed austenite is moderate, and the reverse transformed austenite can generate plastic deformation and deformation under a certain stress level to induce martensitic transformation (Deformation Induced Martensite Transfor)Information, DIMT), to a relatively hard neo-martensitic phase containing a small amount of carbon elements, contributing to additional work hardening. Under the action of the factors, the ultra-high-strength and tough steel prepared by the method has a microstructure (multiple precipitation strengthening phases such as intermetallic compounds and carbides and a large amount of cellular reverse transformation austenite) which is obviously different from that of the traditional ultra-high-toughness steel, and has excellent yield strength and higher fracture toughness than that of the traditional ultra-high-strength and tough steel manufactured by additive.
The 18Ni alloy powder is made of 18Ni series steel belonging to maraging steel; the AerMet100 alloy powder is prepared from AerMet100 steel which belongs to secondary hardening steel. The secondary hardening is a phenomenon in which the hardness of alloy steel containing a carbide forming element such as Cr, mo, V, ti, nb is not lowered but raised to a level close to that of quenched steel when quenched and tempered at 400 to 550 ℃. Steels that are partially heat treated to produce a secondary hardening effect are known as secondary hardened steels.
It is understood that the 18Ni series steel includes one or more of 18Ni (200) steel, 18Ni (250) steel, 18Ni (300) steel, and 18Ni (350) steel, and preferably the 18Ni series steel is 18Ni (300) steel.
In some embodiments, the 18Ni (300) steel comprises the following elements in mass percent: ni:17% -19%; co:8% -10%; mo:4% -6%; ti:0.5% -1.5% and the balance of Fe. It is understood that 18Ni (300) steel may also contain unavoidable impurities (e.g., si, al, mn, O and S, etc.).
In some embodiments, the aeromet 100 steel comprises the following elements in mass percent: ni:11% -13%; co:13% -15%; cr:2% -4%; mo:0.5% -1.5%; c:0.2% -0.3% and the balance of Fe. It will be appreciated that aeromet 100 steel may also contain unavoidable impurities (e.g. Si, al, mn, O and S etc.).
In some embodiments, the 18Ni alloy powder is 20% -80% by mass of the additive manufacturing powder, with the balance being aeromet 100 alloy powder. For example, the 18Ni alloy powder may also be 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%. The mass percentages of the 18Ni alloy powder and the AerMet100 alloy powder are regulated and controlled within the above ranges, so that the ultrahigh-strength high-toughness steel has good processability, yield strength and fracture toughness.
Preferably, the content of the 18Ni alloy powder is 60% -80%, and the balance is AerMet100 alloy powder. The mass percentages of the 18Ni alloy powder and the AerMet100 alloy powder are regulated and controlled within the above ranges, so that the processing performance, the yield strength and the fracture toughness of the ultra-high strength and toughness steel can be further improved.
In some embodiments, the particle size of the 18Ni alloy powder and the aeromet 100 alloy powder are each independently 15 μm to 53 μm. The median particle size of the 18Ni alloy powder and the AerMet100 alloy powder is regulated and controlled within the range, so that the alloy powder is more suitable for the selective laser melting technology.
In a second aspect, the application also provides a preparation method of the ultra-high strength and toughness steel, which comprises the steps S100-S300. The preparation process provided by the application adopts a process route of 'in-situ alloying', namely: the premixed powder prepared by mixing 18Ni alloy powder and AerMet100 alloy powder is used as an additive manufacturing raw material, and the two materials are fused in situ in the additive manufacturing process to obtain a billet with the components between the 18Ni alloy and the AerMet100 alloy, rather than directly smelting the powder with the target components to be used as the additive manufacturing raw material. On one hand, the process route can avoid that Ti and C coexist in a melt in the smelting process to induce carbide liquid separation, and prevent coarse carbide which damages the material performance from being formed; on the other hand, the components of the target steel can be customized by regulating and controlling the proportion of the alloy powder on the basis of ensuring compact molding, so that the diversified mechanical property requirements under different application scenes are met. In addition, the preparation process provided by the application does not need solid solution and quenching treatment, and can simplify the process, reduce energy consumption and avoid size distortion caused by quenching.
Step S100: a premix powder was prepared, comprising an 18Ni alloy powder and an aeromet 100 alloy powder.
In some embodiments, the mixing method employed to prepare the pre-mixed powder is mechanical mixing, e.g., dry blending, i.e., mixing using a dry powder blender. Compared with the ball milling process, the impact force applied to the powder is smaller when the dry powder mixer is used for mixing, so that the problem that the powder cannot maintain the spherical shape due to plastic deformation or splitting/fusing can be avoided, and the powder fluidity is ensured not to be obviously deteriorated.
In the present application, the 18Ni alloy powder and the aeromet 100 alloy powder may be commercially available, or may be prepared by an alloy powder preparation process commonly used in the art. In some embodiments, the method employed to prepare the 18Ni alloy powder and the aeromet 100 alloy powder are each independently selected from gas atomization or rotary electrode atomization. By adopting the two atomization methods, 18Ni alloy powder and AerMet100 alloy powder with average particle sizes suitable for SLM technology can be prepared.
Step S200: and (5) forming the premixed powder prepared in the step S100 into a steel billet by adopting a selective laser melting technology.
In the present application, the technological conditions and parameters of the selective laser melting technique are not limited, and the densified steel can be obtained. As an exemplary illustration, the process of the selective laser melting technique may include the steps of:
the process parameters of the selective laser melting technique may include:
the layering thickness is 15-35 mu m, the scanning line distance is 80-120 mu m, the laser power is 120-250W, the scanning speed is 700-1500 mm/s, and the scanning strategy is as follows: stripe shape (stripe width: 10 mm). The gas atmosphere used in the molding process is an inert gas, such as argon, and the oxygen content in the molding chamber is controlled to be 500 ppm or less.
The equipment adopted by the selective laser melting technology is not limited, and any known equipment can be selected, for example, the equipment can be platinum S210, and the substrate is 316L stainless steel.
It will be appreciated that the shape and size of the billet may be set as desired, and may be a billet of regular shape or a billet of irregular shape.
In some embodiments, after forming the pre-mixed powder into a billet using the selective laser melting technique, a step of cutting is further included to remove the billet from the substrate of the selective laser melting apparatus. The method used for cutting may be wire-cut electric discharge machining.
It will be appreciated that after cutting, the billet may also be subjected to the necessary machining operations, such as turning, milling, abrasive particle stream surface treatments, etc.
Step S300: and (5) performing heat treatment on the steel billet prepared in the step S200 by adopting a direct aging process or a deep cooling aging process. It will be appreciated that the primary purpose of the heat treatment is to: on the premise of not changing the shape and the size of the billet basically, the microstructure is changed, so that the performance of the billet is regulated and controlled, and the mechanical property of the billet meets the requirements of service conditions.
Compared with the traditional heat treatment process of 18Ni (300) steel and AerMet100 steel, the heat treatment process of the ultra-high strength and toughness steel provided by the application is relatively simple, and solution-quenching is not needed. Not only simplifies the heat treatment flow, saves time and energy, but also avoids the oxidation and the size distortion of the steel in the high-temperature heat treatment process.
The steel billet can be obtained through direct aging treatment or cryogenic aging treatment, and the steel product with fine martensitic variants, dispersed nano precipitation in a matrix and a large amount of reverse transformation austenite formed along the cell wall can be obtained. The reverse transformation austenite has proper mechanical stability, and can generate the DIMT at the initial stage of deformation, thereby playing an effective toughening role.
The direct aging process comprises the following steps: and (3) placing the steel billet at 450-500 ℃ for heat preservation for 3-10 hours, and cooling to room temperature.
The cryogenic aging process comprises the following steps: firstly, placing the steel billet at the temperature below-77 ℃ for heat preservation for 0.5-5 h; then heating to room temperature; and then heating to 450-500 ℃, preserving heat for 3-10 hours, and cooling to room temperature. In addition, compared with a direct aging process, the yield strength and fracture toughness of the ultra-high strength and toughness steel can be further improved by adopting a deep cooling aging process.
Preferably, when the mass percentage of the aeromet 100 alloy powder is 25% and the mass percentage of the 18Ni alloy powder is 75%, the heat treatment adopts a cryogenic aging process, wherein the conditions of the cryogenic aging process include:
firstly, placing a steel billet in liquid nitrogen for heat preservation 1 h; then heating to room temperature; then the temperature is raised to 480 ℃, and the mixture is cooled to room temperature after heat preservation of 5 h.
The method of cooling to room temperature is not limited, and a process method commonly used in the art, for example, water quenching, oil quenching, air cooling and the like, may be selected.
According to a specific embodiment, the preparation method of the ultra-high strength and toughness steel comprises the following steps:
1) Preparing 18Ni alloy powder and AerMet100 alloy powder by adopting gas atomization or rotary electrode atomization;
2) Mixing 18Ni alloy powder and AerMet100 alloy powder to prepare premixed powder;
3) Forming the premixed powder into a steel billet by adopting a selective laser melting technology;
4) Separating the billet manufactured in the step 3) from the substrate, and performing heat treatment on the billet by adopting a direct aging process or a cryogenic aging process.
It will be appreciated that depending on the process design of the component, the billet may be machined as necessary before and after the heat treatment.
In a third aspect, the present application further provides an ultra-high strength and toughness steel produced by the production method according to the second aspect.
In some embodiments, the ultra-high strength steel has a yield strength of 1600 MPa, e.g., 1625 MPa, 1640 MPa, 1650 MPa, 1657 MPa, 1700 MPa, 1750 MPa, 1793 MPa, 1800 MPa, 1850 MPa, 1900 MPa, 1920 MPa, 1930 MPa, 1942 MPa, 1952 MPa, 2000 MPa, 2020 MPa, 2050 MPa, 2060 MPa, 2064 MPa.
In some embodiments, the ultra-high strength steel has a yield strength of 1600 MPa~2500 MPa.
In some embodiments, the ultra-high strength and toughness steel has a fracture toughness of greater than or equal to 70 MPa-m 1/2 For example, 72 MPa.m. or more 1 /2 ，≥75 MPa·m 1/2 ，≥75.5 MPa·m 1/2 ，≥78 MPa·m 1/2 ，≥78.2 MPa·m 1/2 ，≥78.5 MPa·m 1 /2 ，≥80 MPa·m 1/2 ，≥85 MPa·m 1/2 。
In some embodiments, the ultra-high strength and toughness steel has a fracture toughness of 70 MPa-m 1/2 ~90 MPa·m 1/2 。
In a fourth aspect, the application also provides an application of the ultra-high strength and toughness steel in manufacturing mechanical parts or forming dies.
The mechanical component is mainly used for aviation, aerospace and navigation equipment, and can be particularly an aircraft landing gear, a wing girder, an aircraft engine shell, a main bearing component for high-precision transmission and the like.
The present application will be described in further detail with reference to specific examples.
Example 1
1) Preparing powder of 18Ni (300) steel and AerMet100 steel by adopting a gas atomization method, wherein the powder is respectively marked as M alloy powder and A alloy powder; the grain sizes of the two kinds of powder are respectively and independently in the range of 15-53 mu M, wherein the median grain size of the M alloy powder is 32 mu M, and the median grain size of the A alloy powder is 35 mu M;
the M alloy powder comprises the following elements in percentage by mass: co:8.97%, ni:18.43%, mo:4.82%, ti:0.98%, cr:0.06%, C:0.02%, O:0.020%, si:0.05%, S:0.0020%, al:0.07%, mn:0.03% and the balance Fe;
the A alloy powder comprises the following elements: co:13.73%, ni:11.37%, cr:3.21%, mo:1.24%, C:0.22%, O:0.024%, si:0.03%, S:0.0013%, al:0.05%, ti:0.04%, mn:0.05% and the balance Fe.
2) And uniformly mixing 50% of M alloy powder and 50% of A alloy powder by mass percent by adopting a dry powder mixer to prepare premixed powder.
3) Forming the premixed powder prepared in the step 2) into a steel billet by adopting a selective laser melting technology, and taking the steel billet off the substrate by adopting wire-cut electric discharge machining; the equipment model adopted by the selective laser melting technology is platinum S210, the substrate is 316L stainless steel, the protective atmosphere in the forming process is argon, and the oxygen content of the forming chamber is below 100 ppm. The process parameters are as follows: the layering thickness is 20 μm, the interval between the melting channels (scanning lines) is 120 μm, the scanning speed is 800 mm/s, the laser power is 150W, the bar scanning strategy is adopted, the bar width is 10 mm, and the interlayer rotation angle is 67 degrees. The billet size is as follows: 31 mm (X direction, powder spreading direction) ×80 mm (Y direction, shielding air flow direction) ×18 mm (Z direction, lamination direction).
4) And 3) carrying out heat treatment on the steel billet prepared in the step 3) by using a muffle furnace and adopting a direct aging process, wherein the heat treatment conditions are as follows: placing the mixture in a muffle furnace with the constant temperature of 480 ℃ for heat preservation of 5 h, and then quenching the mixture to room temperature by water.
Example 2
The preparation method of this example is basically the same as that of example 1, except that: the heat treatment process is a deep cooling aging process. The specific steps of the heat treatment are as follows:
and 3) carrying out heat treatment on the steel billet prepared in the step 3) by using a muffle furnace and adopting a deep cooling aging process, wherein the heat treatment conditions are as follows: incubating 1 h in liquid nitrogen; taking out from liquid nitrogen, placing in air, heating to room temperature, and preserving heat for 5 h; then placing the mixture in a muffle furnace with the constant temperature of 480 ℃ for heat preservation of 5 h, and quenching the mixture to room temperature.
Example 3
The preparation method of this example is basically the same as that of example 1, except that: the mass percentage of the A alloy powder is 25 percent, and the mass percentage of the M alloy powder is 75 percent.
Example 4
The preparation method of this example is basically the same as that of example 2, except that: the mass percentage of the A alloy powder is 25 percent, and the mass percentage of the M alloy powder is 75 percent.
Example 5
The preparation method of this example is basically the same as that of example 1, except that: the mass percentage of the A alloy powder is 75%, and the mass percentage of the M alloy powder is 25%.
Example 6
The preparation method of this example is basically the same as that of example 2, except that: the mass percentage of the A alloy powder is 75%, and the mass percentage of the M alloy powder is 25%.
Comparative example 1
This comparative example was prepared in substantially the same manner as in example 1 except that: the steel billet is prepared by only adopting the alloy A powder.
Comparative example 2
This comparative example was prepared in substantially the same manner as in example 2, except that: preparing a steel billet by only adopting alloy powder A; after the billet is prepared, one-step solution treatment is added before the deep cooling aging heat treatment. Wherein, the solid solution treatment system is as follows: incubate 1 h at 885 ℃, quench with water to room temperature.
Comparative example 3
The preparation method of this comparative example is basically the same as that of comparative example 1, except that: and replacing the alloy powder A with the alloy powder M.
Comparative example 4
The preparation method of this comparative example is basically the same as that of comparative example 2, except that: replacing the alloy powder A with the alloy powder M; and the solution treatment temperature was 900 ℃.
The process parameters such as raw materials and heat treatment in the preparation methods of examples 1 to 6 and comparative examples 1 to 4 are shown in Table 1:
TABLE 1
The steel products prepared in examples 1-6 and comparative examples 1-4 are subjected to compact molding by optical metallographic characterization, and the density is more than 99.5%. FIG. 1 is a scanning electron microscope image of the ultra-high strength and toughness steel (before heat treatment) obtained in example 1. As can be seen from fig. 1, nano-sized spherical carbide particles were found only at the cell-like structure walls of the material, and coarse liquid-out carbides were not found. In practice, in examples 1 to 6, no coarse carbide inclusions were found before and after the heat treatment. FIG. 2 is a transmission electron microscopic view of the ultra-high-strength and toughness steel (after heat treatment) obtained in example 1. As can be seen from FIG. 2, the ultra-high strength and toughness steel after aging treatment has a large number of fine dispersed precipitated phases, wherein part of the precipitated phases have needle-like morphology and are Ni 3 (Ti, mo) precipitated phase, part of the precipitated phase having a granular morphology, M 2 C-type precipitated phase (wherein M is mainly Cr, mo). This experimental phenomenon demonstrates that the aging heat treatment effectively induces the formation of intermetallic and alloy carbide precipitates. These precipitated phases will have a significant strengthening effect on the matrix. FIG. 3 is a scanning electron microscope image of the ultra-high strength and toughness steel (after heat treatment) obtained in example 1. As can be seen from fig. 3, the heat-treated ultra-high-strength steel formed reverse-transformed austenite (protruding region in the figure) distributed along the cell wall, and the volume fraction of the reverse-transformed austenite was approximately 20%. The portion of reverse transformed austenite not only can play a role in coordinating deformation and passivating crack tips, but also can contribute to additional work hardening through the DIMT effect, thereby inhibiting crack propagation in the sample.
The steels produced in examples 1 to 6 and comparative examples 1 to 4 were respectively produced into tensile test specimens and three-point bending test specimens, and were subjected to a static uniaxial tensile test and a fracture toughness test. The test procedure is as follows and the test results are shown in table 2.
In the tensile test, the sample was a plate-like tensile specimen having a gauge length of 10 mm (in the specimen Y direction), a width of 3.7 mm (in the specimen X direction), and a thickness of 2.1 mm (in the specimen Z direction). The relative movement speed of the chuck was 0.5. 0.5 mm/min using a MTS tensile tester.
Fracture toughness testing was performed according to national standard GB/T4161-2007. The sample was a three-point bent sample, with a total length of 65 mm (in the sample Y direction), a width of 15 mm (in the sample Y direction), and a thickness of 7.5 mm (in the sample X direction).
TABLE 2
In terms of strength, the tensile strength of the materials prepared in examples 1-6 is higher than 1950 MPa, and examples 2, 3, 4 and 6 even reach the level of 2 GPa, and the materials belong to typical ultra-high strength steel. The yield strength of the materials prepared in examples 2-4 reached above 1900 MPa, which is at a level comparable to that of the additive manufactured 18Ni (300) steels (comparative examples 3, 4), and significantly better than that of the additive manufactured AerMet100 steels (comparative examples 1, 2). The data illustrate that the materials prepared in examples 1-6 all have excellent strength.
The materials obtained in each of the examples except example 5 had a fracture toughness of 70 MPa.m 1/2 The fracture toughness above is higher than the overall level of comparative examples 1-4. In examples 3, 4 and 6, the fracture toughness of the materials is even close to 80 MPa.m 1/2 . The above data illustrate: by reasonably selecting the material components and the heat treatment process, the material prepared by the premixed powder can have fracture toughness superior to that of 18Ni (300) steel manufactured by additive and AerMet100 steel manufactured by additive on the premise of keeping excellent strength, and the technical advantages of the application are highlighted.
In addition, although the ultra-high strength and toughness steels prepared in examples 1 to 6 have similar tensile strengths, the yield strength is at least 1600 MPa and at most 2 GPa or more. From this, it can be seen that: by adjusting the heat treatment process and the total components of the premixed powder, the material performance (such as yield strength) can be adjusted in a large range, and the space for designing the performance of the ultra-high strength and toughness steel is effectively expanded.
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. The scope of the application is therefore intended to be covered by the appended claims, and the description and drawings should be construed in view of the scope of the appended claims.
Claims (10)
1. The additive manufacturing powder is characterized by comprising 18Ni alloy powder and AerMet100 alloy powder, wherein the content of the 18Ni alloy powder is 20% -80%, and the balance is the AerMet100 alloy powder.
2. The additive manufacturing powder according to claim 1, wherein the 18Ni alloy powder is 60% -80% by weight, and the balance is aeromet 100 alloy powder.
3. The additive manufacturing powder according to any one of claims 1 to 2, wherein the particle diameters of the 18Ni alloy powder and the aeromet 100 alloy powder are 15 μm to 53 μm, respectively and independently.
4. The preparation method of the ultra-high strength and toughness steel is characterized by comprising the following steps of:
preparing premixed powder, wherein the premixed powder comprises 18Ni alloy powder and AerMet100 alloy powder, the content of the 18Ni alloy powder is 20% -80%, and the balance is the AerMet100 alloy powder;
forming the premixed powder into a steel billet by adopting a selective laser melting technology; and
and heat treatment is carried out on the steel billet by adopting a direct aging process or a deep cooling aging process.
5. The method of claim 4, wherein the direct aging process comprises the steps of: placing the steel billet at 450-500 ℃ for heat preservation for 3-10 hours, and cooling to room temperature;
the cryogenic aging process comprises the following steps: firstly, preserving the temperature of the steel billet below-77 ℃ for 0.5-5 h; then heating to room temperature; and then heating to 450-500 ℃, preserving heat for 3-10 hours, and cooling to room temperature.
6. The method of claim 4, wherein the process parameters of the selective laser melting technique include:
the layering thickness is 15-35 mu m, the scanning line distance is 80-120 mu m, the laser power is 150-250W, and the scanning speed is 700 mm/s-1500 mm/s.
7. The method of any one of claims 4 to 6, wherein the method of preparing the pre-mixed powder is dry blending.
8. An ultra-high strength steel, characterized in that it is produced by the production method according to any one of claims 4 to 7.
9. The ultra-high strength and toughness steel according to claim 8, wherein the yield strength of the ultra-high strength and toughness steel is not less than 1600 MPa and fracture toughness is not less than 70 MPa-m 1/2 。
10. Use of the ultra high strength and toughness steel according to claim 8 or 9 in manufacturing mechanical parts or forming dies.
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