CN117620210A - Method for improving fatigue performance of ferrite martensitic steel by arc additive manufacturing and heat treatment - Google Patents
Method for improving fatigue performance of ferrite martensitic steel by arc additive manufacturing and heat treatment Download PDFInfo
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- CN117620210A CN117620210A CN202311650664.8A CN202311650664A CN117620210A CN 117620210 A CN117620210 A CN 117620210A CN 202311650664 A CN202311650664 A CN 202311650664A CN 117620210 A CN117620210 A CN 117620210A
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- 238000004519 manufacturing process Methods 0.000 title claims abstract description 149
- 229910000859 α-Fe Inorganic materials 0.000 title claims abstract description 142
- 238000010438 heat treatment Methods 0.000 title claims abstract description 101
- 238000000034 method Methods 0.000 title claims abstract description 53
- 239000000463 material Substances 0.000 claims abstract description 36
- 229910001566 austenite Inorganic materials 0.000 claims abstract description 34
- 238000009661 fatigue test Methods 0.000 claims abstract description 25
- 238000005498 polishing Methods 0.000 claims description 25
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- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 1
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Classifications
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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]
-
- 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
- B22F10/60—Treatment of workpieces or articles after build-up
- B22F10/64—Treatment of workpieces or articles after build-up by thermal means
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
-
- 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
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Materials Engineering (AREA)
- Thermal Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Crystallography & Structural Chemistry (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Plasma & Fusion (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
The invention relates to a method for improving fatigue performance of ferrite martensitic steel by arc additive manufacturing and heat treatment, which is characterized in that dynamic mechanical fatigue tests are carried out on arc additive manufacturing modified 9Cr-1Mo ferrite martensitic steel after different heat treatments and forged modified 9Cr-1Mo ferrite martensitic steel, and statistics is carried out on the size of prior austenite grains by using electron back scattering diffraction. On the basis of taking the advantages of manufacturing and preparing the modified 9Cr-1Mo ferrite martensitic steel by using arc additive, shortening the production period, manufacturing complex parts without a die and the like into consideration, the fatigue life level same as that of the forged modified 9Cr-1Mo ferrite martensitic steel is achieved, the fatigue strength is superior to that of forging, and the fatigue life of the material is prolonged compared with that of the material by the prior heat treatment method.
Description
Technical Field
The invention relates to the technical field of heat treatment for metal additive manufacturing, in particular to a method for improving the fatigue performance of ferrite martensitic steel by arc additive manufacturing and heat treatment.
Background
With the development of economy, the demand of society for energy is increasing. Nuclear energy is the only new clean energy source that has been demonstrated to provide substantial amounts of electricity in a base load manner. In order to ensure long-term sustainable development of nuclear energy, and promote the nuclear energy to be truly a safe and clean energy source, development of a new generation nuclear energy system must be quickened. The fourth generation nuclear reactor has been the subject of intense research in countries of the world with the economics, safety, reliability and sustainability of its fissile nuclear power system. For the fourth generation nuclear reactor, the material will be subjected to severe operating conditions: high temperature, high neutron irradiation and embrittlement of the material caused by contact with liquid metal. There is therefore a need to find new alloys with good mechanical properties, in particular high temperature creep resistance, corrosion resistance and irradiation resistance. P91 ferrite martensitic steel is obtained by adding a small amount of vanadium (V) and niobium (Nb) into conventional 9Cr-1Mo steel, and the P91 ferrite martensitic steel is the most potential candidate material for fourth generation nuclear reactor components (such as a liquid metal cooling fast propagation reactor steam generator, a pipeline or a spallation target material) due to good stress corrosion resistance, excellent high temperature creep strength, high thermal conductivity and excellent processability, however, in the nuclear power field, for large nuclear components, the conventional forging, casting and other methods are limited by long manufacturing cycle and high cost, and the forged 9Cr-1Mo ferrite martensitic steel has low fatigue strength. The problems can be solved by adopting an additive manufacturing technology, the additive manufacturing can manufacture parts with complex shapes, the time cost is reduced, and the research shows that the 9Cr-1Mo ferrite martensitic steel manufactured by the additive has higher strength. .
At present, the preparation of the modified 9Cr-1Mo ferrite martensitic steel by using an arc additive manufacturing technology is mature, and the modified 9Cr-1Mo ferrite martensitic steel has the advantages of low cost, high material utilization rate, high forming efficiency, high deposition rate and the like. However, nuclear power plant components having a service temperature of 350 ℃ and operating at such temperatures are often subjected to repeated thermal stresses during startup and shutdown of the nuclear reactor operating condition changes due to the temperature gradients in heating and cooling. Cyclic loading due to thermal stress creates severe strain in the material, resulting in low cycle fatigue failure of the engineering components. Arc additive manufacturing materials inevitably have various defects during the manufacturing process, including surface defects such as surface roughness, forming scale precision and the like, and internal defects such as voids, cracks, inclusions, incomplete fusion and the like, the former can be regulated by subsequent machining, the latter cannot be completely eliminated, and therefore, the fatigue performance of the materials can be greatly influenced, and larger residual stress is easily generated in the materials due to the existence of a higher temperature gradient between a molten pool and other areas during the manufacturing process, so that deformation and even cracking are caused. Suitable heat treatment processes will give the material higher strength and good toughness to solve the above problems, however, no published heat treatment method for the modified 9Cr-1Mo ferritic martensitic steel prepared by arc additive manufacturing is disclosed to improve its fatigue properties.
In order to solve the problems, the invention provides a method for improving the fatigue performance of ferrite martensitic steel by arc additive manufacturing and heat treatment, and the feasibility and the practicability of the method are illustrated by comparing the related dynamic mechanical fatigue test data of the material treated by the method, the material treated by the original method and the forging material through dynamic mechanical fatigue test and microscopic characterization.
Disclosure of Invention
The invention aims to overcome the defect that the fatigue life is reduced due to the fact that the microstructure heterogeneity and the performance anisotropy of the arc additive manufacturing (WAAM) ferrite martensitic steel in the prior art are poorer than those of the forged ferrite martensitic steel, and provides a method for improving the fatigue performance of the ferrite martensitic steel by utilizing the advantages that the strength of the arc additive manufacturing ferrite martensitic steel is higher than that of the forged ferrite martensitic steel. The arc additive manufacturing modified 9Cr-1Mo ferrite martensitic steel after heat treatment refines austenite grains and prolongs the fatigue life of the material under the condition that the cyclic softening characteristic of the material is not changed and the strength is higher than that of the forged ferrite martensitic steel.
The invention solves the technical problems by the following technical proposal:
a method for improving the fatigue performance of ferritic martensitic steel by arc additive manufacturing and heat treatment, comprising the following steps:
step 1, preparing modified 9Cr-1Mo ferrite martensitic steel by arc additive manufacturing;
step 2, carrying out heat treatment 1 on the modified 9Cr-1Mo ferrite martensitic steel prepared by the arc additive manufacturing in the step 1:
2.1, carrying out 1200 ℃ solution treatment on the modified 9Cr-1Mo ferrite martensitic steel prepared by the arc additive manufacturing in the step 1, and then carrying out argon quenching after heat preservation for 2 hours;
2.2, carrying out 760 ℃ artificial aging treatment on the modified 9Cr-1Mo ferrite martensitic steel prepared by arc additive manufacturing after 2.1 treatment for 2 hours, and then air-cooling;
step 3, carrying out heat treatment 2 on the modified 9Cr-1Mo ferrite martensitic steel prepared by the arc additive manufacturing in the step 1:
3.1, carrying out 1200 ℃ solution treatment on the modified 9Cr-1Mo ferrite martensitic steel prepared by the arc additive manufacturing in the step 1, and then carrying out argon quenching after heat preservation for 2 hours;
3.2, carrying out 760 ℃ artificial aging treatment on the modified 9Cr-1Mo ferrite martensitic steel prepared by arc additive manufacturing after 3.1 treatment for 2 hours, and then air-cooling;
3.3, carrying out 1200 ℃ solution treatment on the modified 9Cr-1Mo ferrite martensitic steel prepared by arc additive manufacturing after 3.2 treatment, and then carrying out water quenching after heat preservation for 2 hours;
3.4, carrying out 760 ℃ artificial aging treatment on the modified 9Cr-1Mo ferrite martensitic steel prepared by arc additive manufacturing after 3.3 treatment for 2 hours, and then air-cooling;
step 4, respectively processing the modified 9Cr-1Mo ferrite martensitic steel prepared by the arc additive manufacturing heat-treated in the step 2 and the step 3 into rod-shaped samples by machining, and carrying out mechanical polishing and electropolishing treatment on the rod-shaped samples;
step 5, carrying out a dynamic mechanical fatigue test with the strain amplitude of 0.3% -0.7% on the rod-shaped sample obtained in the step 4;
step 6, recording the dynamic mechanical fatigue test data in the step 5 and analyzing the improvement of the fatigue performance of the modified 9Cr-1Mo ferrite martensitic steel prepared by arc additive manufacturing after a heat treatment method;
step 7, counting the prior austenite grain size of the modified 9Cr-1Mo ferrite martensitic steel prepared by the heat-treated arc additive manufacturing obtained in the step 2 by using an electron back scattering diffraction method;
and 8, counting the prior austenite grain size of the modified 9Cr-1Mo ferrite martensitic steel prepared by the heat-treated arc additive manufacturing obtained in the step 3 by using an electron back scattering diffraction method.
Further, in the step 1, a modified 9Cr-1Mo ferrite martensitic steel is prepared by arc additive manufacturing, a forming substrate manufactured by arc additive manufacturing is prepared by adopting a steel plate with the thickness of 10mm, polishing is performed by a steel wire brush, degreasing is performed by a metal cleaning agent, the modified 9Cr-1Mo ferrite martensitic steel is formed on the processed substrate by an arc additive manufacturing technology, the preheating temperature of the substrate is 150 ℃, the welding wire with the diameter of 0.9mm is adopted as a feeding material for preparation, the wire feeding speed is set to be 0.095m/min, the running speed of a welding gun is 10mm/s, the interlayer temperature is 115 ℃, the current is 174A, the voltage is 21.5V, a mixture of 3% CO2 and 97% Ar is used as a protective gas in the additive manufacturing process by adopting a reciprocating additive manufacturing mode, the flow rate of the protective gas is 20L/min, and the obtained modified 9Cr-1Mo ferrite martensitic steel manufactured by arc additive has a plate shape and contains 105 layers, the average height of each layer is about 2.6mm, and the whole size is 300mm×273×29mm.
Further, the step 2 is to put the modified 9Cr-1Mo ferrite martensitic steel prepared by arc additive manufacturing into a box type electric furnace for solution treatment, the temperature in the box type electric furnace is set to be 13 ℃/min, the heating speed is set to be 1200 ℃, and after the heat preservation is carried out for 2 hours, argon is quenched; then, the modified 9Cr-1Mo ferrite martensitic steel manufactured by arc additive is subjected to artificial aging treatment in a box-type electric furnace, the temperature in the box-type electric furnace is set to be 13 ℃/min, the heating speed is set to 760 ℃, the temperature is kept for 2h, and the room temperature air cooling is performed.
Further, the step 3 is to put the modified 9Cr-1Mo ferrite martensitic steel prepared by the arc additive manufacturing treated in the step 2 into a box type electric furnace for solution treatment, the temperature in the box type electric furnace is set to be 13 ℃/min, the heating speed is set to be 1200 ℃, and after the heat preservation is carried out for 2 hours, the room temperature water quenching is carried out; then, the modified 9Cr-1Mo ferrite martensitic steel prepared by arc additive manufacturing is subjected to artificial aging treatment in a box-type electric furnace, the temperature in the box-type electric furnace is set to be 13 ℃/min, the heating speed is set to 760 ℃, the temperature is kept for 2 hours, and the room temperature air cooling is performed.
Further, sampling the modified 9Cr-1Mo ferrite martensitic steel rod-shaped sample prepared by the arc additive manufacturing in the step 4 along the deposition direction, preparing the modified 9Cr-1Mo ferrite martensitic steel prepared by the arc additive manufacturing in the heat treatment 1 and the heat treatment 2 into a rod-shaped sample for dynamic mechanical fatigue test by machining, wherein the length of a gauge length section is 13.5mm, the diameter is 4.5mm, the roughness of the gauge length section is Ra=0.2 mu m, the diameter of a clamping section is 10mm, the length is 38mm, and R20 is taken from an excessive round corner from the clamping section to the gauge length section; and (3) before the dynamic mechanical fatigue test in the step (5), mechanically polishing the modified 9Cr-1Mo ferrite martensitic steel rod-shaped sample prepared by arc additive manufacturing of the heat treatment (1) and the heat treatment (2) and the forged modified 9Cr-1Mo ferrite martensitic steel rod-shaped sample, and then electropolishing for 20s in electrolyte at room temperature under the conditions of 20V voltage and 5A current.
Further, the step 5 uses a hydraulic servo fatigue testing machine with an axial force bearing capacity of + -25 kN to perform a dynamic mechanical fatigue test on the rod-shaped sample obtained in the step 4, wherein the dynamic mechanical fatigue test is controlled by a complete reverse triangle waveform R= -1 at 350 ℃, and the constant strain rate is 1x10 -3 S, strain amplitude is 0.3% -0.7%, induction heating generator with frequency of 15-35kHz is used for rod-shaped sampleHeating was performed by spot welding a 0.25mm diameter k-thermocouple to the center of the cross section of the rod-shaped specimen, holding the rod-shaped specimen at constant temperature for 20 minutes using an induction coil before testing, applying appropriate mechanical strain using a high temperature extensometer measuring 12.5mm in length, and for the hysteresis loop, 800 data points were recorded for each cycle, with a fatigue failure standard of 20% reduction in stress range.
Further, in the step 7, the size of the prior austenite grain of the modified 9Cr-1Mo ferrite martensitic steel prepared by the heat-treated arc additive manufacturing obtained in the step 2 is counted by using an electron back scattering diffraction method, and the preparation flow of an electron back scattering diffraction sample is as follows: sequentially polishing on a polishing machine from coarse to fine by using silica sand paper, rotating a sample by 90 degrees when changing the model of the sand paper, and then using 10% HClO by volume ratio 4 +90％C 2 H 5 And (3) carrying out electrolytic polishing on the OH solution for about 20 seconds under the conditions of 20V voltage and 5A current to remove scratches formed in the last procedure, and using commercial software TSL OIM Analysis 7.0 for post-treatment to reconstruct the prior austenite grain boundaries in the original material IPF by utilizing the OIM software.
Further, in the step 8, the size of the prior austenite grain of the modified 9Cr-1Mo ferrite martensitic steel prepared by the heat-treated arc additive manufacturing obtained in the step 3 is counted by using an electron back scattering diffraction method, and the preparation flow of the electron back scattering diffraction sample is as follows: sequentially polishing on a polishing machine from coarse to fine by using silica sand paper, rotating a sample by 90 degrees when changing the model of the sand paper, and then using 10% HClO by volume ratio 4 +90％C 2 H 5 And (3) carrying out electrolytic polishing on the OH solution for about 20 seconds under the conditions of 20V voltage and 5A current to remove scratches formed in the last procedure, and using commercial software TSL OIM Analysis 7.0 for post-treatment to reconstruct the prior austenite grain boundaries in the original material IPF by utilizing OIM software.
The invention has the advantages and positive effects that:
according to the method for improving the fatigue performance of the ferrite martensitic steel through arc additive manufacturing and heat treatment, the modified 9Cr-1Mo ferrite martensitic steel manufactured through heat treatment is refined in austenite grains under the condition that the cyclic softening characteristic of the material is not changed and the strength is higher than that of the forged ferrite martensitic steel, the fatigue life of the material is improved, and compared with the traditional forged modified 9Cr-1Mo ferrite martensitic steel, the material strength is higher under the condition that the strain amplitude is the same, and the material is allowed to bear larger load. The modified 9Cr-1Mo ferrite martensitic steel manufactured by utilizing the arc additive has the advantage of higher strength, and simultaneously overcomes the defect that the fatigue life of the modified 9Cr-1Mo ferrite martensitic steel manufactured by utilizing the arc additive is lower than that of the forged 9Cr-1Mo ferrite martensitic steel. On the basis of taking into account the advantages of using electric arc additive manufacturing to prepare the modified 9Cr-1Mo ferrite martensitic steel, shortening the production cycle, manufacturing more complex parts without a die and the like, the fatigue life level same as that of forging the modified 9Cr-1Mo ferrite martensitic steel is achieved, the fatigue strength is superior to that of forging, the fatigue life of the additive manufacturing material is prolonged compared with that of the conventional heat treatment method, and the method has very high practical value for engineering application.
Drawings
FIG. 1 is a diagram of a modified 9Cr-1Mo ferritic martensitic steel sheet prepared by molded arc additive manufacturing;
FIG. 2 is a schematic diagram of a heat treatment process;
FIG. 3 is a schematic view of a rod-like sample selection;
FIG. 4 is a schematic drawing of the processing specification of the rod-shaped sample machine;
FIG. 5 (a) shows the relationship between the stress amplitude and fatigue life of heat treatment 1, heat treatment 2 and forging, wherein the strain amplitude is 0.3%;
FIG. 5 (b) shows the relationship between the stress amplitude and fatigue life of heat treatment 1, heat treatment 2 and forging, wherein the strain amplitude is 0.4%;
FIG. 5 (c) shows the relationship between the stress amplitude and fatigue life of heat treatment 1, heat treatment 2 and forging, wherein the strain amplitude is 0.5%;
FIG. 5 (d) shows the relationship between the stress amplitude and fatigue life of heat treatment 1, heat treatment 2 and forging, wherein the strain amplitude is 0.7%;
FIG. 6 is a graph comparing fatigue life of a modified 9Cr-1Mo ferritic martensitic steel prepared by arc additive manufacturing of heat treatment 1, heat treatment 2 with a forged modified 9Cr-1Mo ferritic martensitic steel at a strain magnitude of 0.3% -0.7%;
FIG. 7 (a) is an inverse pole view of prior austenite grains of a modified 9Cr-1Mo ferritic martensitic steel subjected to arc additive manufacturing of heat treatment 1;
FIG. 7 (b) is an inverse pole view of the prior austenite grains of the modified 9Cr-1Mo ferritic martensitic steel subjected to heat treatment 2 arc additive manufacturing;
FIG. 7 (c) is an inverse pole view of the prior austenite grains of the forged modified 9Cr-1Mo ferritic martensitic steel.
In the figure:
5.1-bar-shaped test pieces; 5.2-substrate.
Detailed Description
The invention is further illustrated by the following examples, which are intended to be illustrative only and not limiting in any way.
A method for improving the fatigue performance of ferritic martensitic steel by arc additive manufacturing and heat treatment, comprising the following steps:
step 1, preparing modified 9Cr-1Mo ferrite martensitic steel by arc additive manufacturing;
step 2, carrying out heat treatment 1 on the modified 9Cr-1Mo ferrite martensitic steel prepared by the arc additive manufacturing in the step 1:
2.1, carrying out 1200 ℃ solution treatment on the modified 9Cr-1Mo ferrite martensitic steel prepared by the arc additive manufacturing in the step 1, and then carrying out argon quenching after heat preservation for 2 hours;
2.2, carrying out 760 ℃ artificial aging treatment on the modified 9Cr-1Mo ferrite martensitic steel prepared by arc additive manufacturing after 2.1 treatment for 2 hours, and then air-cooling;
step 3, carrying out heat treatment 2 on the modified 9Cr-1Mo ferrite martensitic steel prepared by the arc additive manufacturing in the step 1:
3.1, carrying out 1200 ℃ solution treatment on the modified 9Cr-1Mo ferrite martensitic steel prepared by the arc additive manufacturing in the step 1, and then carrying out argon quenching after heat preservation for 2 hours;
3.2, carrying out 760 ℃ artificial aging treatment on the modified 9Cr-1Mo ferrite martensitic steel prepared by arc additive manufacturing after 3.1 treatment for 2 hours, and then air-cooling;
3.3, carrying out 1200 ℃ solution treatment on the modified 9Cr-1Mo ferrite martensitic steel prepared by arc additive manufacturing after 3.2 treatment, and then carrying out water quenching after heat preservation for 2 hours;
3.4, carrying out 760 ℃ artificial aging treatment on the modified 9Cr-1Mo ferrite martensitic steel prepared by arc additive manufacturing after 3.3 treatment for 2 hours, and then air-cooling;
step 4, respectively processing the modified 9Cr-1Mo ferrite martensitic steel prepared by the arc additive manufacturing heat-treated in the step 2 and the step 3 into rod-shaped samples by machining, and carrying out mechanical polishing and electropolishing treatment on the rod-shaped samples;
step 5, carrying out dynamic mechanical fatigue test with the strain amplitude of 0.3% -0.7% on the rod-shaped sample obtained in the step 4;
step 6, recording dynamic mechanical fatigue test data in the step 5 and analyzing the improvement of the fatigue performance of the modified 9Cr-1Mo ferrite martensitic steel prepared by arc additive manufacturing after a heat treatment method;
step 7, counting the prior austenite grain size of the modified 9Cr-1Mo ferrite martensitic steel prepared by the heat-treated arc additive manufacturing obtained in the step 2 by using an Electron Back Scattering Diffraction (EBSD) method;
and 8, counting the prior austenite grain size of the modified 9Cr-1Mo ferrite martensitic steel prepared by the heat-treated arc additive manufacturing obtained in the step 3 by using an Electron Back Scattering Diffraction (EBSD) method.
In step 1, a Q345 steel plate with the thickness of 10mm is adopted to prepare a forming substrate for arc additive manufacturing, a steel wire brush is used for polishing and metal cleaning agent degreasing treatment, a modified 9Cr-1Mo ferrite martensitic steel is formed on the processed Q345 substrate through an arc additive manufacturing technology, wherein the preheating temperature of the Q345 substrate is 150 ℃, ER90S-B91 (P91) welding wires with the diameter of 0.9mm are adopted as feeding materials for preparation, the wire feeding speed is set to be 0.095m/min, the running speed of a welding gun is 10mm/S, the interlayer temperature is 115 ℃, the current is 174A, the voltage is 21.5V, a reciprocating additive manufacturing mode is adopted, a mixture of 3 percent CO2 and 97 percent Ar is used as protective gas in the additive manufacturing process, the flow rate of the protective gas is 20L/min, so that oxidation and other pollution to a molten pool in the solidification process are avoided, the stability of the arc and the viscosity of a molten pool are improved, the obtained modified 9Cr-1Mo ferrite martensitic steel manufactured by arc additive is plate-shaped, and comprises 105 deposition layers, wherein the average height of each deposition layer is about 2.6mm, the overall size is 300mm multiplied by 273mm multiplied by 29mm, the modified 9Cr-1Mo ferrite martensitic steel material object manufactured by formed arc additive manufacturing is shown in figure 1, and in the embodiment, the chemical components of the modified 9Cr-1Mo ferrite martensitic steel manufactured by formed arc additive manufacturing are 0.095 weight percent of carbon, 0.21 weight percent of silicon, 0.49 weight percent of manganese, 0.006 weight percent of phosphorus, 0.004 weight percent of sulfur, 8.98 weight percent of chromium, 0.99 weight percent of molybdenum, 0.21 weight percent of vanadium and 0.05 weight percent of niobium.
Step 2, putting the modified 9Cr-1Mo ferrite martensitic steel prepared by arc additive manufacturing into a box-type electric furnace for solution treatment, setting the heating speed of 13 ℃/min in the box-type electric furnace, heating to 1200 ℃, preserving heat for 2 hours, and quenching argon; then, the modified 9Cr-1Mo ferrite martensitic steel manufactured by arc additive is subjected to artificial aging treatment in a box-type electric furnace, the temperature in the box-type electric furnace is set to be 13 ℃/min, the heating speed is set to 760 ℃, the temperature is kept for 2 hours, and the room temperature air cooling is carried out, as shown in figure 2.
Step 3, placing the modified 9Cr-1Mo ferrite martensitic steel prepared by the arc additive manufacturing treated in the step 2 into a box-type electric furnace for solution treatment, setting the heating speed in the box-type electric furnace to be 13 ℃/min, heating to 1200 ℃, preserving heat for 2 hours, and then quenching with water at room temperature; then, the modified 9Cr-1Mo ferrite martensitic steel prepared by arc additive manufacturing is subjected to artificial aging treatment in a box-type electric furnace, the temperature in the box-type electric furnace is set to be 13 ℃/min, the heating speed is set to 760 ℃, the temperature is kept for 2 hours, and the room temperature air cooling is carried out, as shown in figure 2. The modified 9Cr-1Mo ferrite martensitic steel prepared by the arc additive manufacturing through heat treatment eliminates partial residual stress and anisotropy generated in the material due to higher temperature gradient between a molten pool and other areas in the arc additive manufacturing process, so that the modified 9Cr-1Mo ferrite martensitic steel material structure prepared by the arc additive manufacturing has uniform performance.
In step 4, in order to maintain consistency of selected materials, a bar-shaped sample of the modified 9Cr-1Mo ferrite martensitic steel prepared by arc additive manufacturing is sampled along a deposition direction, as shown in fig. 3, the bar-shaped sample is prepared according to national standard design and by machining for dynamic mechanical fatigue test, the geometric shape of the bar-shaped sample is as shown in fig. 4, the length of a gauge length is 13.5mm, the diameter is 4.5mm, the roughness of the gauge length is required Ra=0.2 μm, the diameter of a clamping section is 10mm, the length is 38mm, and the R20 is taken from a transition fillet from the clamping section to the gauge length. In order to reduce the influence of external environmental factors such as corrosion, scratches and the like on the dynamic mechanical fatigue test, before the dynamic mechanical fatigue test in the step 5 is performed, the modified 9Cr-1Mo ferrite martensitic steel rod-shaped sample prepared by arc additive manufacturing of the heat treatment 1 and the heat treatment 2 and the forged modified 9Cr-1Mo ferrite martensitic steel rod-shaped sample are mechanically polished to achieve mirror finish, and then the mirror finish is achieved in an electrolyte (HClO 4 ∶C 2 H 5 Oh=1:9), electropolishing was carried out at room temperature, a voltage of 20V and a current of 5A for 20s.
In step 5, a dynamic mechanical fatigue test was performed on the rod-shaped sample obtained in step 4 using a hydraulic servo fatigue tester (MTS 370.02) having an axial force bearing capacity of ±25kn. Dynamic mechanical fatigue test is controlled by a complete reverse triangle waveform R= -1 at 350 ℃, and constant strain rate is 1x10 -3 The strain amplitude is 0.3% -0.7%, and the temperature of 350 ℃ is selected because the service temperature of the modified 9Cr-1Mo ferrite martensitic steel for the nuclear power station is 350 ℃. To further achieve the desired test temperature, the rod-shaped test specimens were heated using an induction heating generator with a frequency of 15-35 kHz. For temperature control and measurement, a 0.25mm diameter k-type thermocouple was spot welded to the center of the rod-shaped specimen cross section. To obtain a consistent temperature field within the rod-shaped specimen measurement cross section, a home-made induction coil was used to hold the sample at constant temperature for 20 minutes before testing to ensure consistent temperature throughout the sample. Using a high temperature extensometer (Epsilon 7650) measuring 12.5mm in length, apply the appropriateMechanical strain. For the hysteresis loop, 800 data points are recorded per cycle to ensure that the results are accurate. The criteria for fatigue failure is defined as a 20% reduction in stress range.
In step 6, as shown in fig. 5, the response stress peak values of the modified 9Cr-1Mo ferrite martensitic steel prepared by the arc additive manufacturing of the heat treatment 1 and the heat treatment 2 and the forged modified 9Cr-1Mo ferrite martensitic steel under the strain amplitude conditions of 350 ℃,3%, 40%, 50% and 70% can be seen from the change curves of the response stress peak values with the cycle times, the response stress values with the same strain decrease with the increase of the cycle times, and the cycle softening characteristics are shown in the cycle loading process of strain control, so that the heat treatment method in the invention has no influence on the change trend of the cycle stress response. In addition, as can be seen by comparison, the peak stress of the modified 9Cr-1Mo ferritic martensitic steel prepared by the arc additive manufacturing of the heat treatment 2 is basically consistent with that of the modified 9Cr-1Mo ferritic martensitic steel prepared by the arc additive manufacturing of the heat treatment 1, and the peak stress are higher than those of the forged modified 9Cr-1Mo ferritic martensitic steel, and the fatigue life of the modified 9Cr-1Mo ferritic martensitic steel prepared by the arc additive manufacturing is obviously improved compared with that of the modified 9Cr-1Mo ferritic martensitic steel. The method for improving the fatigue performance of the ferrite martensitic steel by arc additive manufacturing and heat treatment is described, on one hand, the advantage of higher strength of the modified 9Cr-1Mo ferrite martensitic steel by arc additive manufacturing is utilized, and meanwhile, the defect that the fatigue life of the modified 9Cr-1Mo ferrite martensitic steel by arc additive manufacturing is lower than that of the forged 9Cr-1Mo ferrite martensitic steel is overcome.
The fatigue life of the modified 9Cr-1Mo ferritic martensitic steel prepared by the arc additive manufacturing of heat treatment 1 and heat treatment 2 is compared with that of the forged modified 9Cr-1Mo ferritic martensitic steel at the strain amplitude of 0.3% -0.7%, as shown in FIG. 6, the fatigue life of the modified 9Cr-1Mo ferritic martensitic steel prepared by the arc additive manufacturing of heat treatment 1 is far lower than that of the forged modified 9Cr-1Mo ferritic martensitic steel at all strain amplitudes, and the fatigue life of the modified 9Cr-1Mo ferritic martensitic steel prepared by the arc additive manufacturing of heat treatment 2 is basically unchanged compared with that of the modified 9Cr-1Mo ferritic martensitic steel prepared by the arc additive manufacturing of heat treatment 1, and the fatigue life of the modified 9Cr-1Mo ferritic martensitic steel is remarkably improved and is equivalent to that of the forged modified 9Cr-1Mo ferritic martensitic steel; at a strain amplitude of 0.4%, the fatigue life increases from 3442 to 3782; at a strain amplitude of 0.5%, the fatigue life increases from 1560 to 2642; at a strain amplitude of 0.7%, the fatigue life increases from 705 to 834. The modified 9Cr-1Mo ferrite martensitic steel prepared by the arc additive manufacturing after heat treatment 2 has obviously improved fatigue mechanical properties compared with the modified 9Cr-1Mo ferrite martensitic steel prepared by the arc additive manufacturing after heat treatment 1, has higher material strength and can bear larger load under the condition of the same strain amplitude compared with the conventional forged modified 9Cr-1Mo ferrite martensitic steel. On the basis of taking the advantages of shortening the production cycle, manufacturing more complex parts without a die and the like into consideration, the modified 9Cr-1Mo ferrite martensitic steel prepared by using the arc additive manufacturing achieves the same fatigue life level as that of the forged modified 9Cr-1Mo ferrite martensitic steel, the fatigue strength is superior to that of the forged modified 9Cr-1Mo ferrite martensitic steel, the fatigue life of the material is improved compared with that of the original heat treatment method, on the one hand, the advantage of higher strength of the modified 9Cr-1Mo ferrite martensitic steel manufactured by using the arc additive manufacturing is overcome, and meanwhile, the defect that the fatigue life of the modified 9Cr-1Mo ferrite martensitic steel manufactured by using the arc additive is lower than that of the forged 9Cr-1Mo ferrite martensitic steel is overcome, and the modified 9Cr-1Mo ferrite martensitic steel has very high practical value for engineering application.
In step 7, the prior austenite grain size of the modified 9Cr-1Mo ferrite martensitic steel prepared by the heat-treated arc additive manufacturing obtained in the step 2 is counted by using an Electron Back Scattering Diffraction (EBSD) method. The preparation process of the electron back scattering diffraction sample comprises the following steps: the method comprises the steps of grinding and polishing silicon oxide sand paper with different mesh numbers on a grinding and polishing machine from coarse to fine, sequentially passing through No. 400, no. 800, no. 1000, no. 1500 and No. 2000, rotating a sample by 90 degrees when the sand paper model is replaced so as to eliminate scratches in the vertical direction generated in the previous working procedure, and then using 10% HClO in volume ratio 4 +90％C 2 H 5 Dissolution of OHAnd (3) carrying out electrolytic polishing for about 20 seconds under the conditions of 20V voltage and 5A current to remove scratches formed in the last procedure, wherein commercial software TSL OIM Analysis 7.0 is used for post-treatment, and the original austenite grain boundary in the original material IPF is reconstructed by utilizing an OIM software.
In step 8, the prior austenite grain size of the modified 9Cr-1Mo ferritic martensitic steel prepared by the heat-treated arc additive manufacturing obtained in the step 3 is counted by using an Electron Back Scattering Diffraction (EBSD) method. The preparation process of the electron back scattering diffraction sample comprises the following steps: the method comprises the steps of grinding and polishing silicon oxide sand paper with different mesh numbers on a grinding and polishing machine from coarse to fine, sequentially passing through No. 400, no. 800, no. 1000, no. 1500 and No. 2000, rotating a sample by 90 degrees when the sand paper model is replaced so as to eliminate scratches in the vertical direction generated in the previous working procedure, and then using 10% HClO in volume ratio 4 +90％C 2 H 5 And (3) carrying out electrolytic polishing on the OH solution for about 20 seconds under the conditions of 20V voltage and 5A current to remove scratches formed in the last procedure, and using commercial software TSL OIM Analysis 7.0 for post-treatment to reconstruct the prior austenite grain boundaries in the original material IPF by utilizing OIM software.
Generally, as the austenitizing temperature increases, austenite grains will grow progressively, with the higher the temperature, the more pronounced the grain growth. Austenitic grain growth is a spontaneous process because of irregular atomic arrangement at grain boundaries and therefore high energy. At higher temperatures, atomic diffusion is easier, so that grains are swallowed with each other to reduce the grain boundary surface area and the grain surface energy, thereby growing austenite grains. The result of austenite grain growth is that the mechanical properties, particularly plasticity and toughness, of the steel after cooling are reduced, resulting in deterioration of the properties, however, the heat treatment method described in the present patent results in a finer prior austenite grain of the modified 9Cr-1Mo ferritic martensitic steel produced by arc additive manufacturing. FIG. 7 shows the prior austenite grain antipode diagrams of a modified 9Cr-1Mo ferritic martensitic steel prepared by arc additive manufacturing of heat treatment 1, heat treatment 2 and a forged modified 9Cr-1Mo ferritic martensitic steel. FIG. 7 (a) shows that the prior austenite grain size of the modified 9Cr-1Mo ferritic martensitic steel prepared by arc additive manufacturing after heat treatment 1 is about 75 μm, and the size is larger; FIG. 7 (b) shows that the prior austenite grains of the modified 9Cr-1Mo ferritic martensitic steel prepared by arc additive manufacturing after heat treatment 2 of the heat treatment method described in the present patent appear significantly refined, about 18 μm. In order to compare the forged modified 9Cr-1Mo ferritic martensitic steel with the modified 9Cr-1Mo ferritic martensitic steel prepared by the arc additive manufacturing after the heat treatment 2 according to the present invention, fig. 7 (c) also shows the inverse pole diagram of the prior austenite grains of the forged modified 9Cr-1Mo ferritic martensitic steel, and the prior austenite grain size of the forged modified 9Cr-1Mo ferritic martensitic steel is calculated to be 20 μm, which is equivalent to the grain size of the modified 9Cr-1Mo ferritic martensitic steel prepared by the arc additive manufacturing after the heat treatment 2, illustrating the mechanism of macroscopic fatigue mechanical property enhancement based on the refined grains of the modified 9Cr-1Mo ferritic martensitic steel obtained by the additive manufacturing and the heat treatment.
In general, the heat treatment 2 can reduce austenite grains of the modified 9Cr-1Mo ferrite martensitic steel prepared by arc additive manufacturing by more than three times, the strength of the modified 9Cr-1Mo ferrite martensitic steel is obviously higher than that of the modified 9Cr-1Mo ferrite martensitic steel under the condition that the fatigue life is equivalent to that of the forged modified 9Cr-1Mo ferrite martensitic steel, and the defect that the fatigue life of the modified 9Cr-1Mo ferrite martensitic steel prepared by arc additive manufacturing is lower than that of the forged 9Cr-1Mo ferrite martensitic steel is overcome while the modified 9Cr-1Mo ferrite martensitic steel prepared by arc additive manufacturing has the advantage of higher strength.
The embodiments of the present invention and the accompanying drawings are disclosed for illustrative purposes, and it will be understood by those skilled in the art that various substitutions, changes and modifications are possible without departing from the spirit and scope of the invention and the appended claims, and therefore the scope of the invention is not limited to the embodiments and the disclosure of the drawings.
Claims (8)
1. A method for improving fatigue performance of ferrite martensitic steel by arc additive manufacturing and heat treatment is characterized in that: the method comprises the following steps:
step 1, preparing modified 9Cr-1Mo ferrite martensitic steel by arc additive manufacturing;
step 2, carrying out heat treatment 1 on the modified 9Cr-1Mo ferrite martensitic steel prepared by the arc additive manufacturing in the step 1:
2.1, carrying out 1200 ℃ solution treatment on the modified 9Cr-1Mo ferrite martensitic steel prepared by the arc additive manufacturing in the step 1, and then carrying out argon quenching after heat preservation for 2 hours;
2.2, carrying out 760 ℃ artificial aging treatment on the modified 9Cr-1Mo ferrite martensitic steel prepared by arc additive manufacturing after 2.1 treatment for 2 hours, and then air-cooling;
step 3, carrying out heat treatment 2 on the modified 9Cr-1Mo ferrite martensitic steel prepared by the arc additive manufacturing in the step 1:
3.1, carrying out 1200 ℃ solution treatment on the modified 9Cr-1Mo ferrite martensitic steel prepared by the arc additive manufacturing in the step 1, and then carrying out argon quenching after heat preservation for 2 hours;
3.2, carrying out 760 ℃ artificial aging treatment on the modified 9Cr-1Mo ferrite martensitic steel prepared by arc additive manufacturing after 3.1 treatment for 2 hours, and then air-cooling;
3.3, carrying out 1200 ℃ solution treatment on the modified 9Cr-1Mo ferrite martensitic steel prepared by arc additive manufacturing after 3.2 treatment, and then carrying out water quenching after heat preservation for 2 hours;
3.4, carrying out 760 ℃ artificial aging treatment on the modified 9Cr-1Mo ferrite martensitic steel prepared by arc additive manufacturing after 3.3 treatment for 2 hours, and then air-cooling;
step 4, respectively processing the modified 9Cr-1Mo ferrite martensitic steel prepared by the arc additive manufacturing heat-treated in the step 2 and the step 3 into rod-shaped samples by machining, and carrying out mechanical polishing and electropolishing treatment on the rod-shaped samples;
step 5, carrying out a dynamic mechanical fatigue test with the strain amplitude of 0.3% -0.7% on the rod-shaped sample obtained in the step 4;
step 6, recording the dynamic mechanical fatigue test data in the step 5 and analyzing the improvement of the fatigue performance of the modified 9Cr-1Mo ferrite martensitic steel prepared by arc additive manufacturing after a heat treatment method;
step 7, counting the prior austenite grain size of the modified 9Cr-1Mo ferrite martensitic steel prepared by the heat-treated arc additive manufacturing obtained in the step 2 by using an electron back scattering diffraction method;
and 8, counting the prior austenite grain size of the modified 9Cr-1Mo ferrite martensitic steel prepared by the heat-treated arc additive manufacturing obtained in the step 3 by using an electron back scattering diffraction method.
2. The method for improving the fatigue property of the ferrite martensitic steel by arc additive manufacturing and heat treatment according to claim 1, characterized in that: the step 1 is to prepare modified 9Cr-1Mo ferrite martensitic steel by arc additive manufacturing, prepare a forming substrate manufactured by arc additive manufacturing by adopting a steel plate with the thickness of 10mm, polish by a steel wire brush and remove oil by a metal cleaning agent, form the modified 9Cr-1Mo ferrite martensitic steel on the processed substrate by an arc additive manufacturing technology, wherein the preheating temperature of the substrate is 150 ℃, the preparation is carried out by adopting a welding wire with the diameter of 0.9mm as a feeding material, the wire feeding speed is set to be 0.095m/min, the running speed of a welding gun is 10mm/s, the interlayer temperature is 115 ℃, the current is 174A, the voltage is 21.5V, the mixture of 3 percent CO2 and 97 percent Ar is used as protective gas in the additive manufacturing process by adopting a reciprocating additive manufacturing mode, the flow rate of the protective gas is 20L/min, and the obtained modified 9Cr-1Mo ferrite martensitic steel manufactured by arc additive has a plate shape and contains 105 layers, the average height of each layer is about 2.6mm, and the whole size is 300mm multiplied by 273mm multiplied by 29mm.
3. The method for improving the fatigue property of the ferrite martensitic steel by arc additive manufacturing and heat treatment according to claim 1, characterized in that: step 2, placing the modified 9Cr-1Mo ferrite martensitic steel prepared by arc additive manufacturing into a box-type electric furnace for solution treatment, setting the heating speed of 13 ℃/min in the box-type electric furnace, heating to 1200 ℃, preserving heat for 2 hours, and then quenching argon; then, the modified 9Cr-1Mo ferrite martensitic steel manufactured by arc additive is subjected to artificial aging treatment in a box-type electric furnace, the temperature in the box-type electric furnace is set to be 13 ℃/min, the heating speed is set to 760 ℃, the temperature is kept for 2h, and the room temperature air cooling is performed.
4. The method for improving the fatigue property of the ferrite martensitic steel by arc additive manufacturing and heat treatment according to claim 1, characterized in that: step 3, placing the modified 9Cr-1Mo ferrite martensitic steel prepared by the arc additive manufacturing treated in the step 2 into a box-type electric furnace for solution treatment, setting the heating speed in the box-type electric furnace to be 13 ℃/min, heating to 1200 ℃, preserving heat for 2 hours, and then quenching with water at room temperature; then, the modified 9Cr-1Mo ferrite martensitic steel prepared by arc additive manufacturing is subjected to artificial aging treatment in a box-type electric furnace, the temperature in the box-type electric furnace is set to be 13 ℃/min, the heating speed is set to 760 ℃, the temperature is kept for 2 hours, and the room temperature air cooling is performed.
5. The method for improving the fatigue property of the ferrite martensitic steel by arc additive manufacturing and heat treatment according to claim 1, characterized in that: sampling a bar-shaped sample of the modified 9Cr-1Mo ferrite martensitic steel prepared by arc additive manufacturing in the step 4 along a deposition direction, preparing the bar-shaped sample of the modified 9Cr-1Mo ferrite martensitic steel prepared by arc additive manufacturing in the heat treatment 1 and the heat treatment 2 by machining, wherein the bar-shaped sample is used for dynamic mechanical fatigue test, the length of a gauge length section is 13.5mm, the diameter is 4.5mm, the roughness of the gauge length section is required Ra=0.2 mu m, the diameter of a clamping section is 10mm, the length is 38mm, and R20 is taken from an excessive round corner from the clamping section to the gauge length section; and (3) before the dynamic mechanical fatigue test in the step (5), mechanically polishing the modified 9Cr-1Mo ferrite martensitic steel rod-shaped sample prepared by arc additive manufacturing of the heat treatment (1) and the heat treatment (2) and the forged modified 9Cr-1Mo ferrite martensitic steel rod-shaped sample, and then electropolishing for 20s in electrolyte at room temperature under the conditions of 20V voltage and 5A current.
6. The method for improving the fatigue property of the ferrite martensitic steel by arc additive manufacturing and heat treatment according to claim 1, characterized in that: the step 5 is to use a hydraulic servo fatigue testing machine with the axial force bearing capacity of +/-25 kN to carry out dynamic mechanical fatigue test on the rod-shaped sample obtained in the step 4, and the dynamic force is calculated by the dynamic mechanical fatigue testing machineThe chemical fatigue test is controlled by a complete reverse triangular waveform R= -1 at 350 ℃ and the constant strain rate is 1x10 -3 And/s, wherein the strain amplitude is 0.3% -0.7%, an induction heating generator with the frequency of 15-35kHz is adopted to heat a rod-shaped sample, a k-type thermocouple with the diameter of 0.25mm is spot-welded at the center of the section of the rod-shaped sample, the rod-shaped sample is kept at constant temperature for 20 minutes before being tested by using an induction coil, a high-temperature extensometer with the measurement length of 12.5mm is used to apply proper mechanical strain, 800 data points are recorded for a hysteresis loop, and the fatigue failure standard is that the stress range is reduced by 20%.
7. The method for improving the fatigue property of the ferrite martensitic steel by arc additive manufacturing and heat treatment according to claim 1, characterized in that: and 7, counting the prior austenite grain size of the modified 9Cr-1Mo ferrite martensitic steel prepared by the heat-treated arc additive manufacturing obtained in the step 2 by using an electron back scattering diffraction method, wherein the preparation flow of an electron back scattering diffraction sample is as follows: sequentially polishing on a polishing machine from coarse to fine by using silica sand paper, rotating a sample by 90 degrees when changing the model of the sand paper, and then using 10% HClO by volume ratio 4 +90％C 2 H 5 And (3) carrying out electrolytic polishing on the OH solution for about 20 seconds under the conditions of 20V voltage and 5A current to remove scratches formed in the last procedure, and using commercial software TSL OIM Analysis 7.0 for post-treatment to reconstruct the prior austenite grain boundaries in the original material IPF by utilizing the OIM software.
8. The method for improving the fatigue property of the ferrite martensitic steel by arc additive manufacturing and heat treatment according to claim 1, characterized in that: and 8, counting the prior austenite grain size of the modified 9Cr-1Mo ferrite martensitic steel prepared by the heat-treated arc additive manufacturing obtained in the step 3 by using an electron back scattering diffraction method, wherein the preparation flow of an electron back scattering diffraction sample is as follows: sequentially polishing on a polishing machine from coarse to fine by using silica sand paper, rotating a sample by 90 degrees when changing the model of the sand paper, and then using 10% HClO by volume ratio 4 +90％C 2 H 5 And (3) carrying out electrolytic polishing on the OH solution for about 20 seconds under the conditions of 20V voltage and 5A current to remove scratches formed in the last procedure, and using commercial software TSL OIM Analysis 7.0 for post-treatment to reconstruct the prior austenite grain boundaries in the original material IPF by utilizing OIM software.
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