Low-cost corrosion-resistant ultrahigh-toughness steel for laser additive manufacturing and heat treatment method of low-cost corrosion-resistant ultrahigh-toughness steel

Abstract

The invention relates to the technical field of laser additive manufacturing and corrosion-resistant ultrahigh-toughness steel, in particular to low-cost corrosion-resistant ultrahigh-toughness steel for laser additive manufacturing and a heat treatment method of the low-cost corrosion-resistant ultrahigh-toughness steel. According to the method, block alloy steel is prepared by adopting a laser directional energy deposition technology, and heat treatment is performed after one-step tempering. Wherein the alloy steel comprises the following chemical components in percentage by weight: 0.1-0.2% of C; 13.0% to 16.0% of Cr; 1.5%-3.5% of Ni; 0.5%-1.0% of Si; 0.7% to 1.2% of Mn; 0.3%-0.7% of Al; 0.2%-0.8% of Cu, and the balance Fe and inevitable impurities. According to the method, relatively cheap alloy elements are adopted, a traditional multi-step post-heat treatment process is abandoned, and the bottleneck problems of high cost, long flow and poor corrosion resistance of existing laser additive manufacturing of the ultrahigh strength and toughness steel are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser additive manufacturing and corrosion-resistant ultra-high strength and toughness steel, and particularly relates to a low-cost corrosion-resistant ultra-high strength and toughness steel for laser additive manufacturing and a heat treatment method thereof. BACKGROUND

[0002] Ultra-high strength and toughness steel has been applied in important fields of national economy such as aerospace, marine transportation and the like due to its excellent comprehensive mechanical properties. However, the current laser additive manufactured ultra-high strength and toughness steel such as 300M, Amert100 and 18Ni300 generally has the following two problems: first, insufficient corrosion resistance, which cannot meet the stringent requirements of the service environment such as marine transportation on the corrosion resistance of the material; and second, complex heat treatment, the traditional laser prepared ultra-high strength and toughness steel needs to be subjected to multi-step post-heat treatment processes such as solid solution + tempering to realize the matching of strength and toughness, but the complex heat treatment process leads to high energy consumption and long cycle, thus seriously limiting its large-scale industrial application.

[0003] In the prior art, patent CN120400706A discloses a high strength and toughness steel based on laser rapid melting, which is characterized in that the alloying components of the high strength and toughness steel are composed of the following mass percentages of elements: C: 0.1~0.3%, Mn: 0.1~2.6%, Ni: 0.1~1.5%, Mo: 0.1~4.0%, W: 1.0~4.5%, Si: 0.1~1.2%, the balance being Fe and unavoidable impurity elements, and the impurity elements include P≤0.01% and S≤0.02%; wherein the ratio of the sum of the mass percentages of Ni and Mn to the mass percentage of Si is not less than 1.572; the high strength and toughness steel needs to be subjected to off-site infrared ultrafast heat treatment (temperature 750~800 ℃, then holding for 3~5 min) to obtain the strength and toughness performance (yield strength≥1200 MPa, V-type notch impact energy≥120 J), but the corrosion resistance is not concerned, and the comprehensive performance is far inferior to the performance of the ultra-high strength and toughness corrosion-resistant steel in the present application.

[0004] Patent CN119859779A discloses a low-cost ultra-high strength martensitic age-hardening steel suitable for additive manufacturing, which has the following chemical components in terms of mass percentage: C:≤0.03%, Ni: 13.0~15.0%, Mo: 2.5~3.5%, Cr: 2.5~3.5%, Mn: 1.3~2.5%, Ti: 0.50~0.80%, Al: 0.05~0.15%, Si≤0.10%, S≤0.010%, P≤0.010%, and the balance being Fe. After the martensitic age-hardening steel is made into wire or powder and then subjected to additive manufacturing, the formed piece is treated by solid solution at 700~850 ℃ for 1h + aging at 400~500 ℃ for 6h, and the tensile strength of the formed piece is not less than 1600 MPa, and the elongation after fracture is not less than 8.0%.

[0005] The invention needs two-step heat treatment to obtain excellent strength and toughness, the production cost is higher, and the corrosion resistance is not concerned. Therefore, developing a low-cost, short-process, super high strength and toughness steel with ultra-high strength, high elongation and excellent corrosion resistance for laser additive manufacturing can meet the urgent needs of key components of complex forming and rapid repair in national major fields such as aerospace. SUMMARY

[0006] In order to overcome the shortcomings of the prior art, the purpose of the present application is to provide a low-cost corrosion-resistant super high strength and toughness steel for laser additive manufacturing and a heat treatment method thereof. Compared with the traditional super high strength and toughness steel, the low-cost corrosion-resistant super high strength and toughness steel for laser additive manufacturing reduces the content of the expensive Ni element in the composition, and does not contain Co and other elements, controls the content of Cr element at 13.0-16.0%, induces the precipitation of nanoscale ε-Cu and NiAl phase and increases the content of martensite through simple one-step post-heat treatment, improves plasticity through transformation induced plasticity (TRIP) and residual stress release, and improves corrosion resistance by using precipitated phase to inhibit Cr-poor behavior, and finally realizes the comprehensive improvement of strength, toughness and corrosion resistance.

[0007] In order to achieve the above-mentioned purpose, the present application realizes the following technical scheme: A low-cost corrosion-resistant super high strength and toughness steel for laser additive manufacturing, the chemical composition of the steel is as follows: C 0.1%-0.2%; Cr 13.0%-16.0%; Ni 1.5%-3.5%; Si 0.5%-1.0%; Mn 0.7%-1.2%; Al 0.3%-0.7%; Cu 0.2%-0.8%, the balance is Fe and unavoidable impurity elements S≤0.01%, P≤0.01%.

[0008] Preferably, the microstructure of the corrosion-resistant super high strength and toughness steel is composed of lath martensite, austenite, carbide and nanoscale precipitated phase.

[0009] Carbide is formed to provide precipitation strengthening, and at the same time promote martensitic transformation, which helps to improve the strength, but the excessive addition of C will increase the carbon equivalent, which will cause large internal stress in the formed part during the process of laser rapid melting (cooling rate 10 3-8 K / s), and the tendency of such internal stress increase increases with the increase of C content. On the other hand, excessive C will form large-size carbide, which will deteriorate the performance of the material. Therefore, the content of C is controlled at 0.1-0.2% in the present application, which not only ensures the strengthening effect, but also avoids the cracking caused by the increase of internal stress, and realizes high quality forming with high density (99%).

[0010] Cr is a key element to improve corrosion resistance, which promotes the formation of a dense passivation film on the surface of steel, significantly improving the corrosion resistance of the material in oxidizing media. Cr can also improve the strength and wear resistance of steel, and inhibit decarburization during heat treatment. However, Cr can significantly reduce the martensite transformation start temperature (Ms), and excessive content will increase the amount of retained austenite, which is not conducive to strength improvement. Therefore, the Cr content should be controlled within 13.0%~16.0%, which can ensure good corrosion resistance while maintaining sufficient martensite transformation.

[0011] Ni can produce significant solid solution strengthening effect, which can improve the strength while maintaining good toughness. Ni and Cr can further improve the hardenability of the steel, which is beneficial to obtain full martensite structure during laser rapid melting. In addition, Ni has little contribution to carbon equivalent, which helps to inhibit the tendency of thermal cracking during rapid solidification. However, as a strong austenite stabilizing element, excessive content of Ni will significantly reduce the Ms point, thereby inhibiting the martensite transformation and leaving too much austenite in the structure, which is not conducive to achieving ultra-high strength. On the other hand, if the content of Ni is too low, it will not be able to fully exert its solid solution strengthening and hardenability improvement effect. Therefore, the content of Ni should be controlled within 1.5%~3.5%, which can ensure the forming quality while considering strength and toughness.

[0012] Si has strong solid solution strengthening effect, which can significantly improve the strength of steel. Si can also inhibit the precipitation of cementite and improve the tempering stability. However, when the content of Si exceeds 1.0%, it will strongly increase the tendency of brittle phase precipitation, induce temper brittleness, and reduce impact toughness. Therefore, the content of Si should be limited within 0.5%~1.0% to balance the strength and toughness.

[0013] Mn is used as a deoxidizer to improve the mechanical properties of steel. Mn is an austenite stabilizing element, and excessive addition will significantly reduce the Ms temperature, resulting in excessive residual austenite and weakening the material strength. In addition, high Mn will promote the formation of banded MnS inclusions, which will damage the toughness. Therefore, the content of Mn should be controlled within 0.7%~1.2% to ensure good deoxidation and hardenability while avoiding the decline of microstructure stability.

[0014] Al mainly plays a role in deoxidation and nitrogen fixation in steel, refines the grain, and improves the strength. Al can also inhibit the precipitation of carbides, promote the formation of intermetallic compounds to strengthen the matrix, and improve the oxidation resistance of steel. Al is a ferrite stabilizing element, and excessive content will promote the formation of δ-ferrite, which will damage the uniformity and cutting performance of the material. Therefore, the content of Al should be limited within 0.3%~0.7% to balance its strengthening effect and microstructure control.

[0015] The element Cu can significantly improve the corrosion resistance of the steel (especially in neutral and acidic environments), and produce precipitation strengthening effect by aging precipitation of ε-Cu phase, further improving the strength. However, excessive Cu content is easy to cause "copper brittleness" phenomenon during hot working, reduce the hot ductility, and may deteriorate the welding performance. Therefore, the Cu content is controlled at 0.2%~0.8%.

[0016] The balance is Fe and impurity elements S≤0.01%, P≤0.01% inevitably mixed in the manufacturing.

[0017] To achieve the above object, the application is realized by the following technical scheme: A preparation method of low-cost corrosion-resistant ultra-high strength and toughness steel for laser additive manufacturing, characterized in that it comprises the following steps: Step S1: obtaining the corrosion-resistant ultra-high strength and toughness steel powder by non-vacuum nitrogen gas atomization; Step S2: putting the corrosion-resistant ultra-high strength and toughness steel powder prepared in step S1 into a drying box, and drying at a temperature of 60℃ for 24h; Step S3: using the corrosion-resistant ultra-high strength and toughness steel powder as raw material and the iron-based material as substrate, and using the laser directional energy deposition technology to prepare the corrosion-resistant ultra-high strength and toughness steel; the equipment used in the laser directional energy deposition technology includes a laser, a deposition head and a numerical control working platform, and the substrate is fixed on the numerical control working platform; the process parameters involved in the laser directional energy deposition technology are as follows: the distance between the deposition head and the substrate is 9~12 mm, the laser wavelength is 1064~1080 mm, the laser focal length is 180~220 mm, the defocusing amount is 23~28 mm, the laser spot diameter is 1.2~1.6 mm, the laser power is 450~550 W, the laser scanning speed is 550~650 mm / min, the powder feeding speed is 4~14 g / min, the overlap coefficient is 0.45~0.55, the protective gas flow is 8~18 L / min, and the powder feeding gas flow is 10~14 L / min; the protective gas and the powder feeding gas are both high-purity nitrogen; Step S4: carrying out tempering heat treatment on the corrosion-resistant ultra-high strength and toughness steel prepared in step S3.

[0018] Preferably, the parameters of the tempering heat treatment in step S4 are as follows: the tempering temperature is 400~500℃, and the holding time is 4-8h.

[0019] Preferably, the heat treatment is carried out using a common box-type heat treatment furnace.

[0020] Preferably, the corrosion-resistant ultra-high strength and toughness steel powder is prepared by non-vacuum nitrogen gas atomization.

[0021] Preferably, the average particle size of the corrosion-resistant ultra-high strength and toughness steel powder is 50~70 μm, and the powder must be dried before use.

[0022] Preferably, the iron-based material is flattened and dried before use.

[0023] Preferably, the corrosion-resistant ultra-high strength and toughness steel contains the following elements by mass percentage: C 0.1%~0.2%; Cr 13.0%~16.0%; Ni 1.5%~3.5%; Si 0.5%~1.0%; Mn 0.7%~1.2%; Al 0.3%~0.7; Cu 0.2%~0.8%, the balance being Fe and unavoidable impurity elements S≤0.01%, P≤0.01%.

[0024] The beneficial effects and advantages of the present application are as follows: (1) Compared with the prior art, the low-cost corrosion-resistant ultra-high strength and toughness steel for laser additive manufacturing and the heat treatment method thereof provided by the present application realize multi-element synergistic alloying by reasonably matching multi-element alloying elements and strictly controlling the content range of each element, especially the content range of high-cost elements, obtain more excellent comprehensive performance under lower alloy content, and the composition design is more flexible and the cost control is more advantageous.

[0025] (2) The present application ingeniously combines the advantages of laser directional energy deposition technology and simple one-step heat treatment, thereby avoiding the problems of high energy consumption, long cycle, low parameter fault tolerance rate and the like caused by traditional multi-step post-heat treatment, to adapt to batch production of multi-size workpieces. The obtained heat-treated steel (YS: 1350~1550 MPa, UTS: 1500~1750 MPa, EL: 10~16%, corrosion rate 0.005~0.010 mm / a) has a large improvement in comprehensive performance compared with the deposited state (YS: 950~1150 MPa, UTS: 1150~1400 MPa, EL: 5~8 %, corrosion rate 1.0~1.4 mm / a).

[0026] The technical solutions of the present application will be further described in detail below with the aid of drawings and examples. DETAILED DESCRIPTION

[0027] Figure 1 It is a low-cost corrosion-resistant ultra-high strength and toughness steel for laser additive manufacturing and a heat treatment method implementation step diagram.

[0028] Figure 2 It is a non-vacuum nitrogen atomized Fe-15Cr-3.2Ni-0.8Mn-0.6Cu-0.56Si-0.4Al-0.16C corrosion-resistant ultra-high strength and toughness steel powder morphology and particle size distribution diagram.

[0029] Figure 3X-ray diffraction (XRD) patterns of as-cast and heat treated Fe-15Cr-3.2Ni-0.8Mn-0.6Cu-0.56Si-0.4Al-0.16C corrosion resistant ultrahigh strength and toughness steel.

[0030] Figure 4 Scanning electron microscope (SEM) morphologies of as-cast and heat treated Fe-15Cr-3.2Ni-0.8Mn-0.6Cu-0.56Si-0.4Al-0.16C corrosion resistant ultrahigh strength and toughness steel.

[0031] Figure 5 Microhardness distribution of as-cast and heat treated Fe-15Cr-3.2Ni-0.8Mn-0.6Cu-0.56Si-0.4Al-0.16C corrosion resistant ultrahigh strength and toughness steel.

[0032] Figure 6 Tensile stress-strain curves of as-cast and heat treated Fe-15Cr-3.2Ni-0.8Mn-0.6Cu-0.56Si-0.4Al-0.16C corrosion resistant ultrahigh strength and toughness steel.

[0033] Figure 7 Potentiodynamic polarization curves and electrochemical impedance spectroscopy of as-cast and heat treated Fe-15Cr-3.2Ni-0.8Mn-0.6Cu-0.56Si-0.4Al-0.16C corrosion resistant ultrahigh strength and toughness steel.

[0034] Figure 8 SEM morphologies of as-cast and heat treated Fe-12.1Cr-2.1Ni-0.75Cu-0.7Mn-0.59Si-0.3Al-0.13C corrosion resistant ultrahigh strength and toughness steel.

[0035] Figure 9 Tensile stress-strain curves of as-cast and heat treated Fe-12.1Cr-2.1Ni-0.75Cu-0.7Mn-0.59Si-0.3Al-0.13C corrosion resistant ultrahigh strength and toughness steel.

[0036] Figure 10 SEM morphologies of as-cast and heat treated Fe-13.85Cr-3.12Ni-0.78Si-0.76Mn-0.69Cu-0.64Al-0.15C corrosion resistant ultrahigh strength and toughness steel.

[0037] Figure 11Tensile curve diagram of Fe-13.85Cr-3.12Ni-0.78Si-0.76Mn-0.69Cu-0.64Al-0.15C corrosion resistant ultra-high strength and toughness steel in as-deposited and heat treated state.

[0038] Figure 12 SEM diagram of Fe-14.44Cr-1.81Ni-1.08Mn-0.74Si-0.64Al-0.37Cu-0.11C corrosion resistant ultra-high strength and toughness steel in as-deposited and heat treated state.

[0039] Figure 13 Tensile curve diagram of Fe-14.44Cr-1.81Ni-1.08Mn-0.74Si-0.64Al-0.37Cu-0.11C corrosion resistant ultra-high strength and toughness steel in as-deposited and heat treated state.

[0040] Figure 14 SEM diagram of Fe-14.44Cr-1.81Ni-1.08Mn-0.74Si-0.64Al-0.37Cu-0.11C corrosion resistant ultra-high strength and toughness steel in as-deposited and heat treated state.

[0041] Figure 15 Tensile curve diagram of Fe-14.44Cr-1.81Ni-1.08Mn-0.74Si-0.64Al-0.37Cu-0.11C corrosion resistant ultra-high strength and toughness steel in as-deposited and heat treated state. DETAILED DESCRIPTION

[0042] In order to make the personnel in the art better understand the scheme of the present application, the present application will be further described below in combination with embodiments and drawings. Obviously, the described embodiments are only some of the embodiments of the present application, and cannot be used as a limitation on the protection scope of the present application.

[0043] The raw materials used in the embodiments of the present application are all obtained through conventional commercial channels.

[0044] Embodiment 1, a low-cost corrosion resistant ultra-high strength and toughness steel for laser additive manufacturing, the chemical composition of the steel is as follows: C 0.1%~0.2%; Cr 13.0%~16.0%; Ni 1.5%~3.5%; Si 0.5%~1.0%; Mn 0.7%~1.2%; Al 0.3%~0.7%; Cu 0.2%~0.8%, the balance is Fe and inevitable impurity elements S≤0.01%, P≤0.01%.

[0045] Preferably, the microstructure of the corrosion resistant ultra-high strength and toughness steel consists of lath martensite, austenite, carbides and nanometer precipitates. The balance is Fe and the impurity elements S≤0.01%, P≤0.01% inevitably mixed in the manufacturing.

[0046] Specifically, in Example 2, the chemical composition of the corrosion resistant ultra-high strength and toughness steel Fe-15Cr-3.2Ni-0.8Mn-0.6Cu-0.56Si-0.4Al-0.16C is as follows: C 0.16%; Cr 15.00%; Ni 3.20%; Si 0.56%; Mn 0.80%; Al 0.40%; Cu 0.60%, and the balance is Fe and the impurity elements S≤0.01%, P≤0.01% inevitably mixed in the manufacturing.

[0047] Specifically, in Example 3, the chemical composition of the corrosion resistant ultra-high strength and toughness steel Fe-12.10Cr-2.10Ni-0.75Cu-0.70Mn-0.59Si-0.30Al-0.13C is as follows: C 0.13%; Cr 12.1%; Ni 2.1%; Si 0.59%; Mn 0.7%; Al 0.3%; Cu 0.75%, and the balance is Fe and the impurity elements S≤0.01%, P≤0.01% inevitably mixed in the manufacturing.

[0048] Specifically, in Example 4, the chemical composition of the corrosion resistant ultra-high strength and toughness steel Fe-13.85Cr-3.12Ni-0.78Si-0.76Mn-0.69Cu-0.64Al-0.15C is as follows: C 0.15%; Cr 13.85%; Ni 3.12%; Si 0.78%; Mn 0.76%; Al 0.64%; Cu 0.69%, and the balance is Fe and the impurity elements S≤0.01%, P≤0.01% inevitably mixed in the manufacturing.

[0049] Specifically, in Example 5, the chemical composition of the corrosion resistant ultra-high strength and toughness steel Fe-14.44Cr-1.81Ni-1.08Mn-0.74Si-0.64Al-0.37Cu-0.11C is as follows: C 0.11%; Cr 14.44%; Ni 1.81%; Si 0.74%; Mn 0.80%; Al 0.64%; Cu 0.37%, and the balance is Fe and the impurity elements S≤0.01%, P≤0.01% inevitably mixed in the manufacturing.

[0050] Specifically, the chemical composition of the corrosion-resistant ultra-high strength and toughness steel Fe-15.69Cr-2.64Ni-0.89Mn-0.86Si-0.57Al-0.26Cu-0.17C in Example 6 is as follows: C 0.17%; Cr 15.69%; Ni 2.64%; Si 0.86%; Mn 0.89%; Al 0.57%; Cu 0.26%, and the balance is Fe and impurity elements S≤0.01%, P≤0.01% inevitably mixed in the manufacturing process.

[0051] To achieve the above object, the present application is realized by the following technical scheme: As shown in Figure 1 The preparation method of the low-cost corrosion-resistant ultra-high strength and toughness steel for laser additive manufacturing in Example 7 comprises the following steps: Step S1: obtaining the corrosion-resistant ultra-high strength and toughness steel powder by non-vacuum nitrogen gas atomization; Step S2: placing the corrosion-resistant ultra-high strength and toughness steel powder prepared in step S1 into a drying box and drying at a temperature of 60℃ for 24h; Step S3: using the corrosion-resistant ultra-high strength and toughness steel powder as raw material and the iron-based material as substrate to prepare the corrosion-resistant ultra-high strength and toughness steel by laser directed energy deposition technology; the equipment used in the laser directed energy deposition technology includes a laser, a deposition head and a numerical control working platform, and the substrate is fixed on the numerical control working platform; the process parameters involved in the laser directed energy deposition technology are as follows: the distance between the deposition head and the substrate is 9-12 mm, the laser wavelength is 1064-1080 mm, the laser focal length is 180-220 mm, the defocusing amount is 23-28 mm, the laser spot diameter is 1.2-1.6 mm, the laser power is 450-550 W, the laser scanning speed is 550-650 mm / min, the powder feeding speed is 4-14 g / min, the overlap coefficient is 0.45-0.55, the protective gas flow is 8-18 L / min, and the powder feeding gas flow is 10-14 L / min; the protective gas and the powder feeding gas are both high-purity nitrogen; Step S4: performing tempering heat treatment on the corrosion-resistant ultra-high strength and toughness steel prepared in step S3.

[0052] Preferably, the parameters of the tempering heat treatment in step S4 are as follows: the tempering temperature is 400-500℃, and the holding time is 4-8h.

[0053] Preferably, the heat treatment is performed using a common box-type heat treatment furnace.

[0054] Preferably, the corrosion-resistant ultra-high strength and toughness steel powder is prepared by non-vacuum nitrogen gas atomization.

[0055] Preferably, the average particle size of the corrosion-resistant ultra-high strength and toughness steel powder is 50-70 μm, and the corrosion-resistant ultra-high strength and toughness steel powder must be dried before use.

[0056] Preferably, the iron-based material is subjected to a flattening treatment before drying.

[0057] The following is a specific embodiment 8 to illustrate the use of low-cost corrosion-resistant ultra-high strength and toughness steel and its heat treatment method by laser additive manufacturing. The Fe-15Cr-3.2Ni-0.8Mn-0.6Cu-0.56Si-0.4Al-0.16C corrosion-resistant ultra-high strength and toughness steel custom powder raw material obtained by non-vacuum nitrogen gas atomization is prepared by laser directed energy deposition technology and then subjected to a simple one-step tempering heat treatment (tempering temperature is 480℃, holding time is 6h).

[0058] The particle size range of the Fe-15Cr-3.2Ni-0.8Mn-0.6Cu-0.56Si-0.4Al-0.16C corrosion-resistant ultra-high strength and toughness steel custom powder is 20-90μm, which is normally distributed. The powder is placed in a drying oven at a temperature of 60℃ for 24h before being used for laser directed energy deposition preparation.

[0059] Fe-15Cr-3.2Ni-0.8Mn-0.6Cu-0.56Si-0.4Al-0.16C corrosion-resistant ultra-high strength and toughness steel is prepared by laser directed energy deposition technology using Fe-15Cr-3.2Ni-0.8Mn-0.6Cu-0.56Si-0.4Al-0.16C corrosion-resistant ultra-high strength and toughness steel powder as raw material and 45 steel as substrate. The equipment used in the laser directed energy deposition technology includes a laser, a deposition head and a numerical control working platform. The substrate is fixed on the numerical control working platform. The process parameters involved in the laser directed energy deposition technology are as follows: the distance between the deposition head and the substrate is 10mm, the laser wavelength is 1070mm, the laser focal length is 200mm, the defocusing amount is 25mm, the laser spot diameter is 1.4mm, the laser power is 500W, the laser scanning speed is 600mm / min, the powder feeding speed is 4.5g / min, the overlap coefficient is 0.5, the protective gas flow is 10L / min, the powder feeding gas flow is 10L / min, and the protective gas and the powder feeding gas are both high-purity nitrogen.

[0060] Detection and analysis: The morphology and particle size distribution of the Fe-15Cr-3.2Ni-0.8Mn-0.6Cu-0.56Si-0.4Al-0.16C corrosion-resistant ultra-high strength and toughness steel powder obtained by non-vacuum nitrogen gas atomization in this embodiment are shown in Figure 2 It can be seen that the powder has a high degree of sphericity, fewer satellite balls and adhesions, and a high surface finish. The particle size range is 20-90μm, which is normally distributed, and the average particle size is 58.7μm. This morphology is beneficial to improving the powder flowability and powder laying uniformity, meeting the strict requirements of the laser additive manufacturing process on the powder particle morphology, and contributing to the manufacturing of high-density and defect-free formed parts.

[0061] The XRD patterns of Fe-15Cr-3.2Ni-0.8Mn-0.6Cu-0.56Si-0.4Al-0.16C corrosion-resistant ultra-high strength and toughness steel in both deposited and heat-treated states are shown below. Figure 3 As shown in the figure, the comparison shows that after one-step heat treatment, the content of martensite phase in the steel increases (75.7% in the deposited state and 82.3% in the heat-treated state), accompanied by the precipitation of NiAl and α-Cu.

[0062] The SEM morphology of corrosion-resistant ultra-high strength and toughness steel in deposited and heat-treated states is shown in the following figures: Fe-15Cr-3.2Ni-0.8Mn-0.6Cu-0.56Si-0.4Al-0.16C. Figure 4 As shown in the figure. A comparison reveals that the amount of precipitated phase in the sample significantly increases after one heat treatment step. For example... Figure 4 (b) As shown in the illustration, a large number of nano-precipitates appear in the martensitic laths of the heat-treated sample. These finely distributed precipitates can effectively hinder dislocation movement and produce a significant precipitation strengthening effect.

[0063] The microhardness and tensile curves of Fe-15Cr-3.2Ni-0.8Mn-0.6Cu-0.56Si-0.4Al-0.16C corrosion-resistant ultra-high strength and toughness steel in deposited and heat-treated states are shown in the figure. Figure 5 , Figure 6 As shown, the overall mechanical properties of the material are significantly improved after a single tempering treatment. Specifically, the microhardness in the heat-treated state reaches 487 HV. 0.2 Compared to the sedimentary state (424 HV) 0.2 The tensile strength increased by approximately 14.9%; the ultimate tensile strength reached 1712 MPa, an increase of approximately 25% compared to the sedimentary state (1370 MPa); and the elongation increased from 8.7% in the sedimentary state to 15.5%, approximately twice. These performance changes indicate that one-step tempering treatment can effectively promote a good balance between strength and toughness.

[0064] Potentiodynamic polarization curves and electrochemical impedance spectroscopy of corrosion-resistant ultra-high strength and toughness steel in deposited state, heat-treated state, and laser-prepared AISI 420 stainless steel are shown in the following figures: Figure 7 As shown, the corrosion resistance of the three, from highest to lowest, is as follows: heat-treated state > AISI 420 > deposited state. From... Figure 7 The polarization curve of a shows the corrosion potential of the heat-treated sample. E corr The corrosion current density is 168.8 mV higher than that of the deposited state and 85 mV higher than that of AISI 420; J corrCompared to the sedimentary state and AISI 420, it decreased by 2.5 × 10⁻⁶. -5 A / cm 2 and 1.2×10 -5 A / cm 2 This indicates that the anodic dissolution process of the heat-treated sample was significantly suppressed. Electrochemical impedance spectroscopy (EIS) Figure 7 (c~d) further confirms that the heat-treated sample has the best corrosion resistance, and its charge transfer resistance (R) is... t ) reaching 17253 Ω·cm 2 The values ​​are respectively sedimentary state (3704 Ω·cm). 2 ) and AISI 420 (6236 Ω·cm) 2 The capacitance was 4.7 times and 2.8 times that of the deposited state and AISI 420, respectively. Furthermore, the capacitive arc radius of the heat-treated sample was significantly larger than that of the deposited state and AISI 420, reflecting the superior barrier ability of its surface protective film. These results indicate that one-step tempering followed by heat treatment (480℃×6h) can significantly improve the corrosion resistance of Fe-15Cr-3.2Ni-0.8Mn-0.6Cu-0.56Si-0.4Al-0.16C corrosion-resistant ultra-high strength and toughness steel, and is superior to AISI 420 stainless steel produced by laser additive manufacturing.

[0065] The following specific example 9 illustrates the use of laser additive manufacturing to produce low-cost corrosion-resistant ultra-high strength and toughness steel and its heat treatment method. The customized powder raw material of corrosion-resistant ultra-high strength and toughness steel, Fe-12.1Cr-2.1Ni-0.75Cu-0.7Mn-0.59Si-0.3Al-0.13C, obtained by non-vacuum nitrogen atomization, is prepared by laser directional energy deposition technology and then subjected to a simple one-step tempering heat treatment (tempering temperature is 480℃, holding time is 4h).

[0066] The application discloses a Fe-12.1Cr-2.1Ni-0.75Cu-0.7Mn-0.59Si-0.3Al-0.13C corrosion-resistant super high strength and toughness steel, which is prepared by using Fe-12.1Cr-2.1Ni-0.75Cu-0.7Mn-0.59Si-0.3Al-0.13C corrosion-resistant super high strength and toughness steel powder as raw material and 45 steel as a substrate through a laser directed energy deposition technology. The laser directed energy deposition technology uses a laser, a deposition head and a numerical control working platform. The substrate is fixed on the numerical control working platform. Process parameters involved in the laser directed energy deposition technology are as follows: the distance between the deposition head and the substrate is 10 mm, the laser wavelength is 1070 mm, the laser focal length is 200 mm, the defocusing amount is 25 mm, the laser spot diameter is 1.4 mm, the laser power is 480 W, the laser scanning speed is 600 mm / min, the powder feeding speed is 4.5 g / min, the overlap coefficient is 0.5, the protective gas flow is 10 L / min, the powder feeding gas flow is 10 L / min, and the protective gas and the powder feeding gas are both high-purity nitrogen.

[0067] The SEM morphologies of the Fe-12.1Cr-2.1Ni-0.75Cu-0.7Mn-0.59Si-0.3Al-0.13C corrosion-resistant super high strength and toughness steel in a deposited state and a heat-treated state are shown in Figs. 1 and 2. Figure 8 As shown in Figs. 1 and 2, the density and quantity of precipitated phases in the sample are obviously increased after one-step heat treatment. Figure 8 As shown in the inserted drawing of Fig. 3, a large number of nano-precipitated phases appear in the martensite laths of the heat-treated sample. These fine and dense precipitated phases act as effective obstacles for dislocation movement, and produce significant precipitated strengthening.

[0068] The tensile curves of the Fe-12.1Cr-2.1Ni-0.75Cu-0.7Mn-0.59Si-0.3Al-0.13C corrosion-resistant super high strength and toughness steel in the deposited state and the heat-treated state are shown in Fig. 4. Figure 9 As shown in Fig. 4, the comprehensive mechanical properties of the material are obviously improved after one-step tempering treatment, and the excellent strength and toughness synergistic effect is exhibited. Specifically, the ultimate tensile strength reaches 1682 MPa, which is about 21% higher than that in the deposited state (1387 MPa); the elongation is increased from 8.6% in the deposited state to 14.5%, about 1.7 times. The above performance changes show that one-step tempering treatment can effectively promote the good matching of strength and toughness.

[0069] The following illustrates the low-cost corrosion-resistant ultra-high strength and toughness steel and its heat treatment method using laser additive manufacturing with specific example 10. The Fe-13.85Cr-3.12Ni-0.78Si-0.76Mn-0.69Cu-0.64Al-0.15C corrosion-resistant ultra-high strength and toughness steel custom powder raw material obtained by non-vacuum nitrogen atomization is subjected to a simple one-step tempering heat treatment (tempering temperature is 430°C, and holding time is 6h) after being prepared by laser directed energy deposition technology.

[0070] The Fe-13.85Cr-3.12Ni-0.78Si-0.76Mn-0.69Cu-0.64Al-0.15C corrosion-resistant ultra-high strength and toughness steel is prepared by laser directed energy deposition technology using Fe-13.85Cr-3.12Ni-0.78Si-0.76Mn-0.69Cu-0.64Al-0.15C corrosion-resistant ultra-high strength and toughness steel powder as raw material and 45 steel as substrate. The equipment used in the laser directed energy deposition technology includes a laser, a deposition head, and a numerical control working platform. The substrate is fixed on the numerical control working platform. The process parameters involved in the laser directed energy deposition technology are as follows: the distance between the deposition head and the substrate is 11 mm, the laser wavelength is 1070 mm, the laser focal length is 200 mm, the defocusing amount is 25 mm, the laser spot diameter is 1.4 mm, the laser power is 480 W, the laser scanning speed is 600 mm / min, the powder feeding speed is 4.8 g / min, the overlap coefficient is 0.5, the protective gas flow is 12 L / min, and the powder feeding gas flow is 10 L / min. The protective gas and the powder feeding gas are both high-purity nitrogen.

[0071] The SEM morphologies of the Fe-13.85Cr-3.12Ni-0.78Si-0.76Mn-0.69Cu-0.64Al-0.15C corrosion-resistant ultra-high strength and toughness steel in the as-deposited state and the heat-treated state are shown in Figure 10 As can be seen by comparison, a large number of second phases are precipitated by one-step heat treatment. As shown in Figure 10 (b) of the drawing, a large number of nanometer precipitates are generated inside the martensite laths of the heat-treated sample. These fine and dense distributed precipitates can effectively hinder dislocation movement and produce significant precipitation strengthening effect.

[0072] The tensile curves of the Fe-13.85Cr-3.12Ni-0.78Si-0.76Mn-0.69Cu-0.64Al-0.15C corrosion-resistant ultra-high strength and toughness steel in the as-deposited state and the heat-treated state are shown in Figure 11As shown, the comparison can be seen, one step tempering process makes its comprehensive mechanical properties synergistic enhancement. The specific performance is: the ultimate tensile strength from the deposited state of 1289 MPa increases to 1585 MPa, about 23% higher; At the same time, the elongation is also increased from 8.9% to 15.2%, about 1.7 times. The results confirm that one step tempering process realizes the synchronous optimization of material strength and toughness.

[0073] The following is a specific embodiment 11 to illustrate the use of low-cost corrosion-resistant ultra-high strength and toughness steel and its heat treatment method by laser additive manufacturing, Fe-14.44Cr-1.81Ni-1.08Mn-0.74Si-0.64Al-0.37Cu-0.11C corrosion-resistant ultra-high strength and toughness steel custom powder raw material obtained by non-vacuum nitrogen gas atomization, after preparation by laser directional energy deposition technology, simple one-step tempering heat treatment (tempering temperature is 450℃, holding time is 6h).

[0074] Fe-14.44Cr-1.81Ni-1.08Mn-0.74Si-0.64Al-0.37Cu-0.11C corrosion-resistant ultra-high strength and toughness steel is prepared by laser directional energy deposition technology using 45 steel as the substrate; The equipment used in the laser directional energy deposition technology includes a laser, a deposition head and a numerical control working platform; The substrate is fixed on the numerical control working platform; The process parameters involved in the laser directional energy deposition technology are as follows: the distance between the deposition head and the substrate is 11 mm, the laser wavelength is 1070 mm, the laser focal length is 200 mm, the defocusing amount is 25 mm, the laser spot diameter is 1.4 mm, the laser power is 530 W, the laser scanning speed is 600 mm / min, the powder feeding speed is 4.5 g / min, the overlap coefficient is 0.5, the protective gas flow is 8 L / min, the powder feeding gas flow is 10 L / min, and the protective gas and the powder feeding gas are both high-purity nitrogen.

[0075] The SEM morphology of Fe-14.44Cr-1.81Ni-1.08Mn-0.74Si-0.64Al-0.37Cu-0.11C corrosion-resistant ultra-high strength and toughness steel in the deposited state and the heat treated state is shown in Figure 12 As shown in Figure 12 (b) the illustration, a large number of nanoscale precipitates are formed in the martensite lath of the heat treated sample. The significant hindrance of dislocation movement can be attributed to these fine and dense distributed precipitates, thereby producing a strong precipitation strengthening effect.

[0076] Tensile curves of Fe-14.44Cr-1.81Ni-1.08Mn-0.74Si-0.64Al-0.37Cu-0.11C corrosion-resistant ultra-high strength and toughness steel in as-deposited and heat-treated states are shown in Figure 13 As shown in the figure, after one-step tempering treatment, the comprehensive mechanical properties of the material are significantly improved. Specifically, the ultimate tensile strength reaches 1585 MPa, which is about 23% higher than that of the as-deposited state (1289 MPa); the elongation is increased from 8.9% in the as-deposited state to 15.2%, about 1.7 times. The above performance changes show that one-step tempering treatment can effectively promote the good matching of strength and toughness.

[0077] The following specific example 12 illustrates the use of low-cost corrosion-resistant ultra-high strength and toughness steel and its heat treatment method by laser additive manufacturing. The Fe-15.69Cr-2.64Ni-0.89Mn-0.86Si-0.57Al-0.26Cu-0.17C corrosion-resistant ultra-high strength and toughness steel custom powder raw material is obtained by non-vacuum nitrogen gas atomization, and then subjected to one-step tempering heat treatment (tempering temperature is 430°C, holding time is 6h) after being prepared by laser directed energy deposition technology.

[0078] Fe-15.69Cr-2.64Ni-0.89Mn-0.86Si-0.57Al-0.26Cu-0.17C corrosion-resistant ultra-high strength and toughness steel is prepared by laser directed energy deposition technology using 45 steel as the substrate; the equipment used in the laser directed energy deposition technology includes a laser, a deposition head, and a numerical control working platform; the substrate is fixed on the numerical control working platform; the process parameters involved in the laser directed energy deposition technology are as follows: the distance between the deposition head and the substrate is 11 mm, the laser wavelength is 1070 mm, the laser focal length is 200 mm, the defocusing amount is 25 mm, the laser spot diameter is 1.4 mm, the laser power is 500 W, the laser scanning speed is 600 mm / min, the powder feeding speed is 5.0 g / min, the overlap coefficient is 0.5, the protective gas flow is 10 L / min, the powder feeding gas flow is 10 L / min, and the protective gas and the powder feeding gas are both high-purity nitrogen.

[0079] The SEM morphology of Fe-15.69Cr-2.64Ni-0.89Mn-0.86Si-0.57Al-0.26Cu-0.17C corrosion-resistant ultra-high strength and toughness steel in as-deposited and heat-treated states is shown in Figure 14 As shown in the figure, one-step heat treatment process significantly increases the density of precipitates in the sample. As Figure 14(b) As shown in the insert, a large number of nano-sized precipitates are formed inside the martensitic lath of the heat-treated sample, which can effectively hinder the movement of dislocations and produce a significant precipitation strengthening effect.

[0080] The tensile curves of the as-deposited and heat-treated Fe-15.69Cr-2.64Ni-0.89Mn-0.86Si-0.57Al-0.26Cu-0.17C corrosion-resistant ultra-high strength and toughness steel are shown in Figure 15 As shown in the insert, after one-step tempering treatment, the comprehensive mechanical properties of the material are significantly improved. Specifically, the ultimate tensile strength reaches 1602 MPa, which is about 22% higher than that of the as-deposited state (1312 MPa); the elongation is increased from 7.6% in the as-deposited state to 13.8%, which is about 1.8 times. The above performance changes show that one-step tempering treatment can effectively promote the good matching of strength and toughness.

[0081] The low-cost corrosion-resistant ultra-high strength and toughness steel for laser additive manufacturing and the heat treatment method thereof of the present embodiment realize the synergistic regulation of the mechanical properties and corrosion resistance of the additive manufacturing steel.

[0082] Although the embodiments of the present application have been described above, modifications and substitutions made by those skilled in the art without departing from the principles and spirit of the present application shall fall within the scope of the present application.

Claims

1. A low-cost corrosion-resistant ultra-high strength and toughness steel for laser additive manufacturing, characterized by, The corrosion-resistant super-high strength and toughness steel contains the following elements in the following mass percentages: C 0.1-0.2%; Cr 13.0-16.0%; Ni 1.5-3.5%; Si 0.5-1.0%; Mn 0.7-1.2%; Al 0.3-0.7; Cu 0.2-0.8%, and the balance of Fe and inevitable impurity elements S≤0.01%, P≤0.01%.

2. The low-cost corrosion-resistant ultra-high strength and toughness steel for laser additive manufacturing according to claim 1, characterized in that, The microstructure of the corrosion-resistant super-high strength and toughness steel is composed of lath martensite, austenite, carbide and nano precipitates.

3. A method for preparing a low-cost corrosion-resistant ultra-high strength and toughness steel for laser additive manufacturing, characterized in that, The method comprises the following steps: S1: preparing the corrosion-resistant super-high strength and toughness steel powder; S2: drying the corrosion-resistant super-high strength and toughness steel powder prepared in step S1 in a drying box at a temperature of 60°C for 24 hours; S3: using the corrosion-resistant super-high strength and toughness steel powder as raw material and an iron-based material as substrate, the corrosion-resistant super-high strength and toughness steel is prepared by laser directed energy deposition method; the equipment used in the laser directed energy deposition method comprises a laser, a deposition head and a numerical control working platform, and the substrate is fixed on the numerical control working platform; the process parameters involved in the laser directed energy deposition method are as follows: the distance between the deposition head and the substrate is 9-12 mm, the laser wavelength is 1064-1080 mm, the laser focal length is 180-220 mm, the defocusing amount is 23-28 mm, the laser spot diameter is 1.2-1.6 mm, the laser power is 450-550 W, the laser scanning speed is 550-650 mm / min, the powder feeding speed is 4-14 g / min, the overlap coefficient is 0.45-0.55, the protective gas flow is 8-18 L / min, and the powder feeding gas flow is 10-14 L / min; the protective gas and the powder feeding gas are both high-purity nitrogen; S4: the corrosion-resistant super-high strength and toughness steel prepared in step S3 is subjected to tempering heat treatment.

4. The method of claim 3, wherein, The tempering heat treatment parameters in step S4 are as follows: the tempering temperature is 400-500°C, and the holding time is 4-8 hours.

5. The method of claim 3, wherein, The heat treatment is performed by using a common box-type heat treatment furnace.

6. The method of claim 3, wherein, The corrosion-resistant super-high strength and toughness steel powder is prepared by using non-vacuum nitrogen gas atomization.

7. The method of claim 3, wherein, The average particle size of the corrosion-resistant super-high strength and toughness steel powder is 50-70 μm, and the steel powder must be dried before use.

8. The method of claim 3, wherein, The iron-based material must be flattened and dried before use.

9. The method of claim 3, wherein, The corrosion-resistant super-high strength and toughness steel contains the following elements in the following mass percentages: C 0.1-0.2%; Cr 13.0-16.0%; Ni 1.5-3.5%; Si 0.5-1.0%; Mn 0.7-1.2%; Al 0.3-0.7; Cu 0.2-0.8%, and the balance of Fe and inevitable impurity elements S≤0.01%, P≤0.01%.

Images