Nano-enhanced fine-grain corrosion-resistant alloy for laser additive manufacturing and application of nano-enhanced fine-grain corrosion-resistant alloy

Abstract

The invention provides a nano-reinforced fine-grain corrosion-resistant alloy for laser additive manufacturing, which comprises the following chemical components in percentage by mass: 13.0 to 13.9 percent of Cr, 14.0 to 17.0 percent of Mo, 0.4 to 0.7 percent of Ti, less than or equal to 0.5 percent of Fe, less than or equal to 0.004 percent of C, less than or equal to 0.08 percent of Si, less than or equal to 0.10 percent of Mn, less than or equal to 0.04 percent of P, less than or equal to 0.03 percent of S, less than or equal to 0.10 percent of Co and the balance of Ni and inevitable impurities. And nano chromium carbide (Cr3C2) particle phases are also uniformly dispersed in the alloy. According to the alloy disclosed by the invention, the contents of Cr and C in a nickel-based alloy matrix phase are reduced to be below the standard lower limit, a trace nano Cr3C2 phase is actively introduced, and the effect of a grain refiner in the laser processing process is utilized, so that a finally obtained component has an ultra-fine grain structure, and the corrosion resistance of the component is superior to that of a Hastelloy C4 alloy component manufactured by an additive material in a traditional process.

Description

Technical Field

[0001] This invention relates to the field of high-performance nickel-based corrosion-resistant alloy technology, and in particular to an alloy design and application that significantly refines the solidification structure of laser additive manufacturing by introducing a nano-reinforcing phase, while simultaneously improving its mechanical and corrosion resistance properties. Background Technology

[0002] Hastelloy C4 alloy is widely used in harsh environments due to its excellent corrosion resistance. However, when manufacturing components from this alloy using laser-directed energy deposition (DED-LB) technology, two major challenges arise due to the inherent rapid solidification characteristics of the process:

[0003] (1) During solidification, it is easy to form penetrating coarse columnar crystals, accompanied by significant dendritic segregation. The former will cause the mechanical properties of the component (such as strength and plasticity) to exhibit obvious anisotropy, and it is easy to cause local stress concentration under stress conditions. The latter will destroy the uniformity of the matrix composition, making the segregation area a preferred corrosion point, and deteriorating the original corrosion resistance advantage of the alloy.

[0004] (2) If a reinforcing phase is added to improve strength, traditional carbide phases (such as Cr-rich M) 23 When C6 precipitates at grain boundaries, it will consume a large amount of Cr elements in the matrix that ensure corrosion resistance, and it will also form Cr-depleted zones at grain boundaries, severely damaging the core ability of Hastelloy C4 alloy to resist intergranular corrosion, causing intergranular cracking of components in a short time under corrosive conditions.

[0005] Existing technologies typically involve process adjustments within standard composition ranges, making it difficult to simultaneously achieve significant improvements in grain refinement and corrosion resistance. Therefore, there is an urgent need to develop an innovative material design scheme for the DED-LB process to fundamentally resolve the contradiction between microstructure and properties in additive manufacturing. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing a novel alloy. By reducing the Cr and C content in the matrix phase to below the standard lower limit and actively introducing a trace amount of nano Cr3C2 phase, and utilizing its grain refiner effect during laser processing, the final product is an additively manufactured Hastelloy C4 alloy component with an ultra-fine grain structure and corrosion resistance superior to that of traditional processes.

[0007] According to a first aspect of the present invention, a nano-reinforced fine-grained corrosion-resistant alloy for laser additive manufacturing, the matrix chemical composition of the alloy, by mass percentage, comprises: Cr 13.0%–13.9%, Mo 14.0%–17.0%, Ti 0.4%–0.7%, Fe ≤0.5%, C ≤0.004%, Si ≤0.08%, Mn ≤0.10%, P ≤0.04%, S ≤0.03%, Co ≤0.10%, with the balance being Ni and unavoidable impurities;

[0008] The alloy also contains uniformly dispersed nano-chromium carbide (Cr3C2) particles.

[0009] As an optional implementation, the content of the nano-chromium carbide particle phase is 0.05 wt.% to 0.1 wt.% of the total mass.

[0010] As an optional implementation, the average particle size of the nano-chromium carbide particles is 50 nm to 100 nm.

[0011] As an optional implementation, the mass percentage of Cr is 13.5% to 13.9%.

[0012] As an optional implementation, the mass percentage of C is 0.003% to 0.004%.

[0013] As an optional implementation, the mass percentage of Ti is 0.5% to 0.6%.

[0014] As an optional implementation, the matrix powder and the nano-chromium carbide particle phase powder are mixed by ball milling or powder mixing to ensure that the nano-chromium carbide particle phase powder adheres to the surface of the matrix powder without damaging the sphericity and flowability of the matrix powder, thereby obtaining the alloy powder.

[0015] As an optional implementation, the matrix powder is prepared by vacuum induction melting (VIM) combined with gas atomization (GA) or plasma rotating electrode method (PREP).

[0016] According to a second aspect of the present invention, an application of the aforementioned nano-reinforced fine-grained corrosion-resistant alloy in the manufacture of components using a laser-directed energy deposition process is provided.

[0017] According to a third aspect of the present invention, a component manufactured using a laser additive manufacturing process is provided. The component is made from the aforementioned nano-reinforced fine-grained corrosion-resistant alloy as raw material, and a rough blank is obtained by laser directional energy deposition process followed by solution heat treatment.

[0018] As can be seen from the above technical solutions of the present invention, the nano-reinforced fine-grained corrosion-resistant alloy for laser additive manufacturing proposed in this invention has the following significant beneficial effects:

[0019] 1. Excellent grain refinement effect: The trace amount of nano Cr3C2 particles (≤0.1wt.%) provides a large number of efficient nucleation sites in the molten pool of DED-LB, completely breaking the rule that laser additive manufacturing will inevitably form coarse columnar crystals. For the first time, an ultrafine equiaxed structure with an average grain size of less than 30μm was obtained in C4 alloy without the need for large plastic deformation, which significantly improves the strength, plasticity and fatigue performance of the material.

[0020] 2. Proactive and significant improvement in corrosion resistance: Eliminating sensitization risk at its source, the matrix's extremely low carbon (C≤0.004%) design, combined with controlled Cr content, completely eliminates the formation of any harmful grain boundary Cr-rich carbides (M...) during thermal processes (printing or heat treatment). 23 The possibility of C6 or harmful phases is eliminated, thus fundamentally preventing intergranular corrosion.

[0021] 3. Ultrafine grains and ultra-uniform structure: Ultrafine grain structure means a denser and more stable passivation film. The extremely low C content and the rapid solidification induced by nano-phase work together to greatly reduce the dendritic segregation of elements such as Mo and Cr, and obtain unprecedented micro-uniformity of composition, thereby significantly improving the overall uniform corrosion and pitting corrosion resistance of the component.

[0022] 4. Performance data surpasses tradition: Tests show that the composite material components prepared by this invention have a corrosion rate of less than 5 mm / y under the ASTM G28 B method, and their corrosion resistance has been significantly improved.

[0023] 6. High-density forming: The refined grains improve the flowability of the molten pool, reduce printing defects, and can obtain near-perfect formed parts with a density of over 99.8%. Attached Figure Description

[0024] Figure 1 Comparison chart of tensile strength, yield strength and elongation of components prepared by DED-LB process in Examples 1-2 and Comparative Examples 1-4 of this invention.

[0025] Figure 2 This is a comparison chart of the corrosion rates of components prepared by the DED-LB process in Examples 1-2 and Comparative Examples 1-4 of the present invention. Detailed Implementation

[0026] To better understand the technical content of the present invention, specific embodiments are described below in conjunction with the accompanying drawings.

[0027] Various aspects of the invention are described in this disclosure with reference to the accompanying drawings, in which numerous illustrative embodiments are shown. The embodiments of this disclosure are not necessarily intended to encompass all aspects of the invention. It should be understood that the various concepts and embodiments described above, as well as those described below in more detail, can be implemented in any of a number of ways.

[0028] This invention provides a novel nano-reinforced fine-grained corrosion-resistant alloy that addresses the performance bottleneck of Hastelloy C4 alloy components manufactured using laser additive manufacturing. Its core design concept involves the synergistic regulation of composition, process, microstructure, and properties: by actively reducing the Cr and C content of the matrix to below the lower limit of the standard composition of Hastelloy C4 alloy, and simultaneously introducing trace amounts of nano-Cr3C2 phase, this nano-phase can act as an in-situ grain refiner during the rapid melting-solidification process of laser additive manufacturing, effectively inhibiting the growth of coarse columnar crystals. The resulting component not only forms an ultrafine equiaxed microstructure with an average grain size ≤30μm, but also exhibits significantly superior resistance to intergranular corrosion and harsh media corrosion compared to Hastelloy C4 alloy components manufactured using traditional laser additive manufacturing processes, achieving a synergistic breakthrough in ultrafine grain strengthening and high corrosion resistance.

[0029] In an exemplary embodiment of the present invention, a nano-reinforced fine-grained corrosion-resistant alloy for laser additive manufacturing is provided. The matrix chemical composition of the alloy, by mass percentage, includes: Cr 13.0%–13.9%, Mo 14.0%–17.0%, Ti 0.4%–0.7%, Fe ≤ 0.5%, C ≤ 0.004%, Si ≤ 0.08%, Mn ≤ 0.10%, P ≤ 0.04%, S ≤ 0.03%, Co ≤ 0.10%, with the balance being Ni and unavoidable impurities.

[0030] The alloy also contains uniformly dispersed nano-chromium carbide (Cr3C2) particles.

[0031] In an optional example, the content of nano-chromium carbide particle phase powder is 0.05 wt.% to 0.1 wt.% of the total mass. It is understood that this content refers to the mass percentage of nano-chromium carbide particle phase powder to the total mass of nickel-based alloy matrix powder and nano-chromium carbide particle phase powder.

[0032] In an optional example, the average particle size of the nano-chromium carbide particle phase powder is 50 nm to 100 nm.

[0033] In optional examples, the mass percentage of Cr is 13.5% to 13.9%.

[0034] In the optional example, the mass percentage of C is 0.003% to 0.004%.

[0035] In an optional example, the mass percentage of Ti is 0.5% to 0.6%.

[0036] In optional examples, the mass percentage of Mo is 15.8% to 17%.

[0037] In an optional example, the mass percentage of Fe is ≤0.08%, and the mass percentage of Co is ≤0.07%.

[0038] In an optional example, the mass percentage of Si is ≤0.06%, the mass percentage of Mn is ≤0.05%, and the mass percentage of S is ≤0.00003%.

[0039] In one example, the high corrosion-resistant Ni-Cr-Mo based alloy has the following chemical composition by mass percentage: Cr 13.5%, Mo 15.8%, Ti 0.6%, Fe 0.08%, C 0.003%, Si 0.06%, Mn 0.05%, Co 0.07%, S 0.0003%, P ≤0.04%, with the balance being Ni and unavoidable impurities.

[0040] In another example, a highly corrosion-resistant Ni-Cr-Mo based alloy, by mass percentage, comprises: Cr 13.9%, Mo 15.8%, Ti 0.5%, Fe 0.08%, C 0.004%, Si 0.06%, Mn 0.05%, Co 0.07%, S 0.0003%, P ≤0.04%, with the balance being Ni and unavoidable impurities.

[0041] In an optional example, the matrix powder and the nano-chromium carbide particle phase powder are mixed by ball milling or powder mixing to ensure that the nano-chromium carbide particle phase powder adheres to the surface of the matrix powder without damaging the sphericity and flowability of the matrix powder, thereby obtaining the alloy powder.

[0042] In an optional example, the matrix powder is prepared using vacuum induction melting (VIM) combined with gas atomization (GA) or plasma rotating electrode method (PREP).

[0043] In another exemplary embodiment of the present invention, an application of the aforementioned nano-reinforced fine-grained corrosion-resistant alloy in the manufacture of components using a laser-directed energy deposition process is provided.

[0044] In another exemplary embodiment of the present invention, a component manufactured using a laser additive manufacturing process is provided. The component is made from the aforementioned nano-reinforced fine-grained corrosion-resistant alloy as raw material, and a rough blank is obtained by laser directional energy deposition process followed by solution heat treatment.

[0045] This invention addresses the traditional challenges of laser additive manufacturing of Hastelloy C4 alloys, such as the formation of coarse columnar crystals and the difficulty in simultaneously improving corrosion resistance and mechanical properties. It achieves a performance breakthrough through "introduction of extremely small amounts of nanophases + extreme low-carbon matrix design + reduction of Cr content + active control of Ti content."

[0046] (i) Cr is a strong solid solution strengthening element that significantly increases the stacking fault energy of the matrix and reduces the grain boundary mobility. During the rapid solidification process of the laser molten pool, a high Cr content will make the grain boundaries more stable and strongly inhibit the "heterogeneous nucleation" process. The added nano Cr3C2 particles will be difficult to effectively promote the nucleation of new grains. At the same time, Cr itself will segregate during rapid solidification. The interaction between high Cr content and other alloying elements such as Mo may exacerbate the uneven distribution of solute elements between dendrites and dendrite trunks. In addition, high Cr content is the main factor promoting the precipitation of brittle σ phase (a topological close-packed phase rich in Cr and Mo). σ phase is more likely to form in the heat-affected zone of printing or during improper heat treatment. σ phase is not only brittle and hard itself, but it will also cause Cr and Mo depletion around it, seriously damaging the toughness and corrosion resistance of the material.

[0047] Employing an ultra-low carbon matrix design (C≤0.004%), it eliminates harmful Cr-rich carbides (Mn) at the grain boundaries during thermal processes such as printing or heat treatment, thus fundamentally preventing these carbides. 23 The formation of C6 can completely eliminate the risk of intergranular corrosion.

[0048] Therefore, the matrix is ​​made with reduced Cr and extremely low C content to minimize the precipitation of harmful phases (σ phase, M phase). 23 C6) lays the foundation for the performance of components in terms of composition.

[0049] (II) Based on this, the refined equiaxed grain structure induced by the introduction of nano-Cr3C2 means a significant increase in the total grain boundary area. This makes the passivation film denser and makes pitting corrosion less likely to initiate and propagate at the grain boundaries. At the same time, the extremely low C content and rapid solidification greatly reduce the dendritic segregation of elements such as Mo and Cr. The high uniformity of the microstructure avoids the formation of micro-galvanic cells due to elemental inhomogeneity, providing a guarantee for subsequent processing.

[0050] (iii) Through a high-temperature, short-time, and rapid-cooling solution treatment process, all potential carbides (including added Cr3C2 and possible M) will be ensured. 23C6) is completely dissolved in the γ-Ni austenitic matrix, while simultaneously promoting short-range diffusion of printed Cr and Mo atoms, achieving microscale homogenization. Furthermore, taking advantage of the much stronger affinity of Ti for C than Cr for C, during the cooling process after solution treatment, Ti preferentially combines with C to form more stable and finer TiC particles. These TiC particles are typically dispersed within the grains rather than continuously distributed at grain boundaries; therefore, their impact on corrosion resistance is far less than that of continuous grain boundary M. 23 C6 membrane.

[0051] The final component has a uniform structure with fine equiaxed grains, uniform composition, and no harmful carbide precipitation, and has good corrosion resistance.

[0052] Below, we provide a specific example of preparing a nano-reinforced fine-grained corrosion-resistant alloy and fabricating the desired component using laser-directed energy deposition.

[0053] (1) Preparation of ultra-low carbon and low chromium matrix powder: Vacuum induction melting (VIM) combined with gas atomization (GA) or plasma rotating electrode method (PREP) is used to prepare spherical metal powder with composition that strictly meets the matrix requirements.

[0054] (2) Preparation of nano-reinforced fine-grained corrosion-resistant alloy powder: The above matrix powder and 0.05wt.% to 0.1wt.% nano Cr3C2 powder are uniformly mixed by low-energy ball mill or high-efficiency three-dimensional powder mixer to ensure that the nanoparticles adhere to the surface of the matrix powder without damaging its sphericity and flowability.

[0055] (3) Laser Directed Energy Deposition (DED-LB) Forming: Using the above-mentioned nano-reinforced fine-grained corrosion-resistant alloy powder as raw material, the component is formed using DED-LB technology; wherein, the preferred process parameters are: laser power 1000W~1800W, scanning speed 600mm / min~1000mm / min, and powder feed rate 4g / min~8g / min. In this process, nano-Cr3C2 particles act as heterogeneous nucleation sites, effectively promoting heterogeneous nucleation of the molten pool, significantly refining the solidification structure, and obtaining uniform and fine equiaxed crystals.

[0056] (3) Solution heat treatment: The DED-LB formed components are held at 1120℃~1160℃ for 1~2 hours, followed by water quenching (WQ). This process aims to: (a) eliminate residual printing stress; (b) promote element diffusion and further homogenize the composition; (c) dissolve most of the added nano Cr3C2 particles, and the released Cr and C atoms are incorporated into the γ-Ni matrix, ultimately making the overall Cr content close to the standard range, while the C content remains at an extremely low level (≤0.015%).

[0057] To facilitate better understanding, the present invention will be further illustrated below with several specific examples, but the preparation process is not limited to these examples, and the content of the present invention is not limited to these examples.

[0058] Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0059] The sample prepared in the following example is a block with dimensions of length × width × height = 100mm × 100mm × 100mm.

[0060] Example 1

[0061] Step 1: Preparation of nano-reinforced fine-grained corrosion-resistant alloy powder: First, prepare the matrix powder. Weigh the corresponding raw materials according to the composition (Cr 13.5%, Mo 15.8%, C 0.003%, Fe 0.08%, Ti 0.6%, Silicon (Si): 0.06%, Manganese (Mn): 0.05%, Phosphorus (P): ≤0.04%, Sulfur (S): 0.0003%, Cobalt (Co): 0.07%, Nickel (Ni): balance and unavoidable impurities). Prepare powder rods by vacuum induction melting, and then prepare alloy powder by plasma rotating electrode atomization (PREP). The powder particle size range is 45-150μm, sphericity is 0.95, and flowability is 11.5s / 50g.

[0062] Then, the matrix powder was mixed with 0.08 wt.% of nano Cr3C2 powder (average particle size 70 nm) in a three-dimensional powder mixer for 4 hours to obtain nano-reinforced fine-grained corrosion-resistant alloy powder.

[0063] Step 2, DED-LB forming: Using the above-mentioned nano-reinforced fine-grained corrosion-resistant alloy powder, the sample was printed under the parameters of laser power 1500W, scanning speed 700mm / min, and powder feed rate 12g / min. Metallographic observation showed that its deposited microstructure consisted of exceptionally fine equiaxed crystals with an average grain size of 15μm and a density of 99.85%.

[0064] Step 3, Solution treatment: The printed sample is solution treated at 1140℃ for 1.5 hours, followed by water quenching.

[0065] Step 4, Microstructure and Properties Testing: After solution treatment, the final composition has an overall Cr content of 13.6% and a C content of 0.014%. Microstructure: It is a uniform, ultrafine equiaxed crystal structure with an average grain size of 25 μm.

[0066] Step 5, Corrosion Resistance: After grinding, polishing, and cleaning the surface of the deposited sample, a corrosion test using the ASTM G28 B method was directly performed. After 24 hours of immersion, the corrosion rate was calculated to be approximately 3.0 mm / y by weighing.

[0067] Step 6, Mechanical properties: The room temperature tensile yield strength reaches 335 MPa, the tensile strength reaches 765 MPa, and the elongation remains at 60%. Its strength is significantly better than that of the traditionally prepared C4 alloy.

[0068] Example 2

[0069] Step 1: Preparation of nano-reinforced fine-grained corrosion-resistant alloy powder: First, prepare the matrix powder. Weigh the corresponding raw materials according to the composition (Cr 13.9%, Mo 15.8%, C 0.004%, Fe 0.08%, Ti 0.5%, Silicon (Si): 0.06%, Manganese (Mn): 0.05%, Phosphorus (P): ≤0.04%, Sulfur (S): 0.0003%, Cobalt (Co): 0.07%, Nickel (Ni): balance and unavoidable impurities). Prepare powder rods by vacuum induction melting, and then prepare alloy powder by plasma rotating electrode atomization (PREP). The powder particle size range is 45-150μm, the powder sphericity is 0.94, and the flowability is 11.4s / 50g.

[0070] Then, the matrix powder was mixed with 0.05 wt.% of nano Cr3C2 powder (average particle size 70 nm) in a three-dimensional powder mixer for 4 hours to obtain nano-reinforced fine-grained corrosion-resistant alloy powder.

[0071] Step 2, DED-LB forming: Using the above-mentioned nano-reinforced fine-grained corrosion-resistant alloy powder, the sample was printed under the parameters of laser power 1500W, scanning speed 700mm / min, and powder feed rate 12g / min. Metallographic observation showed that its deposited microstructure consisted of exceptionally fine equiaxed crystals with an average grain size of 18μm and a density of 99.80%.

[0072] Step 3, Solution treatment: The printed sample is solution treated at 1140℃ for 1.5 hours, followed by water quenching.

[0073] Step 4, Microstructure and Properties Testing: After solution treatment, the final composition has an overall Cr content of 13.9% and a C content of 0.01%. Microstructure: It is a uniform, ultrafine equiaxed crystal structure with an average grain size of 28 μm.

[0074] Step 5, Corrosion Resistance: After grinding, polishing, and cleaning the surface of the deposited sample, a corrosion test using ASTM G28 B method was directly performed. After 24 hours of immersion, the corrosion rate was calculated to be approximately 4.0 mm / y by weighing.

[0075] Step 6, Mechanical properties: The room temperature tensile yield strength reaches 330 MPa, the tensile strength reaches 761 MPa, and the elongation remains at 55%. Its strength is significantly better than that of the traditionally prepared C4 alloy.

[0076] Comparative Example 1

[0077] Step 1, Powder Preparation: Weigh the corresponding raw materials according to the composition (Cr: 16.5%, Mo: 14.8%, Ti: 0.26%, Fe: 1.80%, Co: 0.72%, C: 0.012%, Si: 0.044%, Mn: 0.36%, balance Ni and unavoidable impurities). Prepare powder rods by vacuum induction melting, and then prepare alloy powder from the rods by plasma rotating electrode atomization (PREP). The powder particle size range is 45-150μm, the powder sphericity is 0.94, and the flowability is 11.5s / 50g.

[0078] Step 2, DED-LB forming: Using the above powder, the sample was printed under the parameters of laser power 1500W, scanning speed 700mm / min, and powder feed rate 12g / min. Metallographic observation showed that its deposited structure was a typical columnar crystal structure with an average grain size of 95μm and a density of 98.10%.

[0079] Step 3, Solution treatment: The printed sample is solution treated at 1140℃ for 1.5 hours, followed by water quenching.

[0080] Step 4, Microstructure and Properties Testing: After solution treatment, the final composition has an overall Cr content of 16.5% and a C content of 0.012%. Microstructure: The average grain size is 98 μm.

[0081] Step 5, Corrosion Resistance: After grinding, polishing, and cleaning the surface of the deposited sample, a corrosion test using the ASTM G28 B method was directly performed. After 24 hours of immersion, the corrosion rate was calculated to be approximately 15 mm / y by weighing.

[0082] Step 6, Mechanical properties: The room temperature tensile yield strength reaches 330 MPa, the tensile strength reaches 753 MPa, and the elongation remains at 40%. Its strength is significantly better than that of the traditionally prepared C4 alloy.

[0083] Comparative Example 2

[0084] Step 1: Powder Preparation: Weigh the corresponding raw materials according to the composition (Cr: 15.5%, Mo: 14.8%, Ti: 0.26%, Fe: 1.80%, Co: 0.72%, C: 0.014%, Si: 0.044%, Mn: 0.36%, balance Ni and unavoidable impurities). Prepare powder rods using vacuum induction melting, and then process the rods into alloy powder using plasma rotating electrode atomization (PREP). The powder particle size range is 45-150 μm, the powder sphericity is 0.93, and the flowability is 11.9 s / 50 g.

[0085] Step 2, DED-LB forming: Using the above powder, a block sample was printed under the parameters of laser power 1500W, scanning speed 700mm / min, and powder feed rate 12g / min. Metallographic observation showed that its deposited structure was a typical columnar crystal structure with an average grain size of 92μm and a density of 98.12%.

[0086] Step 3, Solution treatment: The printed sample is solution treated at 1140℃ for 1.5 hours, followed by water quenching.

[0087] Step 4, Microstructure and Properties Testing: After solution treatment, the final composition has an overall Cr content of 15.5% and a C content of 0.014%. Microstructure: The average grain size is 95 μm.

[0088] Step 5, Corrosion Resistance: After grinding, polishing, and cleaning the surface of the deposited sample, a corrosion test using the ASTM G28 B method was directly performed. After 24 hours of immersion, the corrosion rate was calculated to be approximately 18 mm / y by weighing.

[0089] Step 6, Mechanical properties: The room temperature tensile yield strength reaches 325 MPa, the tensile strength reaches 745 MPa, and the elongation remains at 42%. Its strength is significantly better than that of the traditionally prepared C4 alloy.

[0090] Comparative Example 3

[0091] Step 1, Powder Preparation: Weigh the corresponding raw materials according to the composition (Cr 13.9%, Mo 15.8%, C 0.004%, Fe 0.08%, Ti 0.25%, Silicon (Si): 0.06%, Manganese (Mn): 0.05%, Phosphorus (P): ≤0.04%, Sulfur (S): 0.0003%, Cobalt (Co): 0.07%, Nickel (Ni): balance and unavoidable impurities). Prepare powder rods by vacuum induction melting, and then prepare alloy powder from the rods by plasma rotating electrode atomization (PREP). The powder particle size range is 45-150μm, sphericity is 0.93, and flowability is 11.8s / 50g.

[0092] Step 2, DED-LB forming: Using the above powder, a block sample was printed under the parameters of laser power 1500W, scanning speed 700mm / min, and powder feed rate 12g / min. Metallographic observation showed that its deposited structure was a typical columnar crystal structure with an average grain size of 96μm and a density of 98.50%.

[0093] Step 3, Solution treatment: The printed sample is solution treated at 1140℃ for 1.5 hours, followed by water quenching.

[0094] Step 4, Microstructure and Properties Testing: After solution treatment, the final composition has an overall Cr content of 13.9% and a C content of 0.004%. Microstructure: The average grain size is 99 μm.

[0095] Step 5, Corrosion Resistance: After grinding, polishing, and cleaning the surface of the deposited sample, a corrosion test using ASTM G28 B method was directly performed. After 24 hours of immersion, the corrosion rate was calculated to be approximately 16 mm / y by weighing.

[0096] Step 6, Mechanical properties: The room temperature tensile yield strength reaches 319 MPa, the tensile strength reaches 740 MPa, and the elongation remains at 40%. Its strength is significantly better than that of the traditionally prepared C4 alloy.

[0097] Comparative Example 4

[0098] Step 1, Powder Preparation: Weigh the corresponding raw materials according to the composition (Cr: 15.5%, Mo: 14.8%, Ti: 0.26%, Fe: 1.80%, Co: 0.72%, C: 0.014%, Si: 0.044%, Mn: 0.36%, balance Ni and unavoidable impurities). Prepare powder rods by vacuum induction melting, and then prepare alloy powder from the rods by plasma rotating electrode atomization (PREP). The powder particle size range is 45-150μm, sphericity is 0.93, and flowability is 11.8s / 50g.

[0099] Then, the matrix powder was mixed with 0.05 wt.% of nano Cr3C2 powder (average particle size 70 nm) in a three-dimensional powder mixer for 4 hours to obtain nano-reinforced fine-grained corrosion-resistant alloy powder.

[0100] Step 2, DED-LB forming: Using the above powder, a block sample was printed under the parameters of laser power 1500W, scanning speed 700mm / min, and powder feed rate 12g / min. Metallographic observation showed that its deposited structure was a typical columnar crystal structure with an average grain size of 20μm and a density of 99.2%.

[0101] Step 3, Solution treatment: The printed sample is solution treated at 1140℃ for 1.5 hours, followed by water quenching.

[0102] Step 4, Microstructure and Properties Testing: After solution treatment, the final composition has an overall Cr content of 13.9% and a C content of 0.004%. Microstructure: The average grain size is 32 μm.

[0103] Step 5, Corrosion Resistance: After grinding, polishing, and cleaning the surface of the deposited sample, a corrosion test using the ASTM G28 B method was directly performed. After 24 hours of immersion, the corrosion rate was calculated to be approximately 14 mm / y by weighing.

[0104] Step 6, Mechanical properties: The room temperature tensile yield strength reaches 335 MPa, the tensile strength reaches 760 MPa, and the elongation remains at 50%. Its strength is significantly better than that of the traditionally prepared C4 alloy.

[0105] The test results of the samples in Examples 1-2 and Comparative Examples 1-2 show that the nano-reinforced fine-grained corrosion-resistant alloy powder of the present invention reduces the Cr and C content of the matrix to below the standard lower limit and actively introduces trace amounts of nano Cr3C2 phase. The laser additive manufacturing components corresponding to this material have an ultra-fine grain structure and corrosion resistance performance superior to that of traditional additive manufacturing special corrosion-resistant alloys.

[0106] The results from Examples 2 and Comparative Examples 2-4 show that only by controlling the matrix composition and introducing trace amounts of nano-Cr3C2 phase can both strength and corrosion resistance be improved simultaneously.

[0107] In summary, the nano-reinforced fine-grained corrosion-resistant alloy of the present invention can achieve high density under the DED-LB process and obtain good plasticity and corrosion resistance.

[0108] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A nano-reinforced fine-grained corrosion-resistant alloy for laser additive manufacturing, characterized in that, The base chemical composition of the alloy, by mass percentage, includes: Cr 13.0%–13.9%, Mo 14.0%–17.0%, Ti 0.4%–0.7%, Fe ≤0.5%, C ≤0.004%, Si ≤0.08%, Mn ≤0.10%, P ≤0.04%, S ≤0.03%, Co ≤0.10%, with the balance being Ni and unavoidable impurities; The alloy also contains uniformly dispersed nano-chromium carbide (Cr3C2) particles.

2. The nano-reinforced fine-grained corrosion-resistant alloy for laser additive manufacturing according to claim 1, characterized in that, The content of the nano-chromium carbide particles is 0.05 wt.% to 0.1 wt.% of the total mass.

3. The nano-reinforced fine-grained corrosion-resistant alloy for laser additive manufacturing according to claim 1, characterized in that, The average particle size of the nano-chromium carbide particles is 50 nm to 100 nm.

4. The nano-reinforced fine-grained corrosion-resistant alloy for laser additive manufacturing according to claim 1, characterized in that, The mass percentage of Cr is 13.5% to 13.9%.

5. The nano-reinforced fine-grained corrosion-resistant alloy for laser additive manufacturing according to claim 1, characterized in that, The mass percentage of C is 0.003% to 0.004%.

6. The nano-reinforced fine-grained corrosion-resistant alloy for laser additive manufacturing according to claim 1, characterized in that, The mass percentage of Ti is 0.5% to 0.6%.

7. The nano-reinforced fine-grained corrosion-resistant alloy for laser additive manufacturing according to claim 1, characterized in that, The matrix powder and the nano-chromium carbide particle phase powder are mixed by ball milling or powder mixing to ensure that the nano-chromium carbide particle phase powder adheres to the surface of the matrix powder without damaging the sphericity and flowability of the matrix powder, thereby obtaining the alloy powder.

8. The nano-reinforced fine-grained corrosion-resistant alloy for laser additive manufacturing according to claim 7, characterized in that, The matrix powder was prepared by vacuum induction melting (VIM) combined with gas atomization (GA) or plasma rotating electrode method (PREP).

9. The application of the nano-reinforced fine-grained corrosion-resistant alloy according to any one of claims 1-8 in the manufacture of components using laser-directed energy deposition (LDED) technology.

10. A component manufactured using laser additive manufacturing technology, characterized in that, The component is made from the nano-reinforced fine-grained corrosion-resistant alloy described in any one of claims 1-8. The rough blank is manufactured by laser directional energy deposition and then subjected to solution heat treatment.

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