Improved MAR-M247 nickel-based alloy suitable for additive manufacturing and design and preparation method of improved MAR-M247 nickel-based alloy

Abstract

The invention discloses an improved MAR-M247 nickel-based alloy suitable for additive manufacturing and a design and preparation method of the improved MAR-M247 nickel-based alloy, and belongs to the technical field of metal additive manufacturing. The improved MAR-M247 nickel-based alloy is prepared from the following chemical components in percentage by mass: 1.0 to 2.0 percent of Ti, 8.0 to 10.0 percent of Cr, 9.0 to 11.0 percent of Co, 9.0 to 11.0 percent of W, 3.0 to 4.0 percent of Ta, 0.5 to 1.5 percent of Mo, 0.01 to 0.03 percent of B, 0.005 to 0.01 percent of Hf, 0.07 to 0.11 percent of C, 4.5 to 5.0 percent of Al, 0.02 to 0.04 percent of Zr and the balance of Ni, and a component calculation and selective laser melting forming technology is adopted in the design and preparation method. On the basis of the MAR-M247 alloy, high compactness of the improved MAR-M247 alloy is achieved by adjusting alloy components and optimizing printing process parameters.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal additive manufacturing, and particularly relates to an improved MAR-M247 nickel-based alloy suitable for additive manufacturing and its design and preparation method. Background Art

[0002] MAR-M247 nickel-based alloy exhibits excellent mechanical properties, corrosion resistance and oxidation resistance under high-temperature conditions, and is widely used in core hot-end components such as aero-engine turbine blades, combustion chambers, and turbine disks. Selective laser melting technology can form parts with complex structures, reduce material waste and shorten the production cycle. However, during the additive manufacturing process of MAR-M247 alloy, due to the repeated heating of the cladding layer, the previous deposited layer is in the aging temperature range and continuously precipitates γ' phase, and dislocations continuously accumulate around the γ' phase to generate stress concentration; at the same time, the high temperature gradient causes the enrichment of C element at the grain boundary, increases the carbide content, and increases the cracking tendency of cracks; the uneven temperature gradient and rapid solidification cooling during the additive manufacturing process are extremely likely to cause the generation of thermal stress, and a large number of cracks are generated in the alloy under the combined action, seriously affecting the mechanical properties of the material. Summary of the Invention

[0003] Object of the Invention: The first object of the present invention is to provide an improved MAR-M247 nickel-based alloy with high density suitable for additive manufacturing, and the second object of the present invention is to provide a design and preparation method for the above-mentioned improved MAR-M247 nickel-based alloy suitable for additive manufacturing.

[0004] Technical Solution: The improved MAR-M247 nickel-based alloy suitable for additive manufacturing provided by the present invention, by mass percentage, includes the following chemical components: Ti 1.0-2.0%, Cr 8.0-10.0%, Co 9.0-11.0%, W 9.0-11.0%, Ta 3.0-4.0%, Mo 0.5-1.5%, B 0.01-0.03%, Hf 0.005-0.01%, C 0.07-0.11%, Al 4.5-5.0%, Zr 0.02-0.04%, and the balance is Ni.

[0005] Preferably, the improved MAR-M247 nickel-based alloy, by mass percentage, includes the following chemical components: Ti 1.0%, Cr 8.4-10.0%, Co 10%, W 10%, Ta 3.0%, Mo 0.7%, B 0.015%, Hf 0.005-0.01%, C 0.07-0.0875%, Al 4.5-4.75%, Zr 0.02-0.04%, and the balance is Ni.

[0006] More preferably, the improved MAR-M247 nickel-based alloy, by mass percentage, comprises the following chemical components: Ti 1.0%, Cr 8.4%, Co 10%, W 10%, Ta 3.0%, Mo 0.7%, B 0.015%, Hf 0.005%, C 0.0875%, Al 4.75%, Zr 0.02 - 0.03%, and the balance is Ni.

[0007] Based on the commercial MAR-M247 alloy, the present invention changes the element contents of C, Al, and Zr, and the tendency of the alloy to generate cracks at room temperature and high temperature is reduced. The raw material ratio used in the present invention should be strictly implemented according to the above requirements. If the addition ratio of C is too large, excessive carbides will be generated inside the alloy, making the alloy brittle; if the addition ratio of C is too small, the solidification temperature range will increase, and the crack tendency will increase. If the content of Al is less than 4.5%, the precipitation amount of γ' phase decreases rapidly, and the tensile strength of the material decreases. Adding Zr element can improve the morphology of carbides and enhance the ductility of the alloy, but excessive addition will lead to an increase in the cracking tendency of the material and an increase in crack density.

[0008] The present invention also provides a design and preparation method for the above-mentioned improved MAR-M247 nickel-based alloy suitable for additive manufacturing, comprising the following steps:

[0009] (1) Optimize the contents of C, Al, and Zr on the basis of the original MAR-M247: Analyze the influence law of the change of the content of a single element in C, Al, and Zr on the equilibrium phase characteristic parameters by thermodynamic calculation; on this basis, orthogonally design the alloy composition, and take the low solidification cracking index SCI as the calculation criterion, screen out all composition points with SCI ≤ 2000, obtain the optimized composition range, and obtain the composition of the improved MAR-M247 nickel-based alloy.

[0010] (2) Optimize the additive manufacturing process of the improved MAR-M247 nickel-based alloy obtained in step (1). The optimized process parameters include: laser power, laser scanning speed, laser scanning spacing, and powder spreading thickness. Form specimens under the optimized process parameters to finally obtain the MAR-M247 nickel-based alloy suitable for additive manufacturing.

[0011] Further, in step (1), the equilibrium phase characteristic parameters include γ' phase and carbides; the formula of the SCI is: SCI = |dT / d(f s 1 / 2 )|.

[0012] Further, in step (2), the laser power is 90 - 115 W, the laser scanning speed is 800 - 1000 mm / s, the scanning pitch is 0.03 - 0.06 mm, and the powder spreading thickness is 0.03 - 0.07 mm; the forming method is selective laser melting technology, the scanning strategy is reciprocating scanning within a layer, rotating 67° between layers, and high-purity argon gas is used as the shielding gas.

[0013] Principle of the invention: In the present invention, first, the contents of C, Al, and Zr elements are reduced on the basis of the original MAR-M247. For example, the nominal content of C is 0.15 wt.%, and the designed contents are 0.05 wt.%, 0.10 wt.%, and 0.12 wt.%. The influence rules of the change of the content of a single element in C, Al, and Zr on the characteristic parameters such as γ' phase and carbides are analyzed by thermodynamic calculation. Based on the above rules, considering the interaction of multiple elements, 9 alloy compositions conforming to the orthogonal rule are designed. Then, taking the low solidification cracking index (SCI) as the calculation criterion, all composition points with SCI ≤ 2000 are screened out. Range analysis is carried out on the screened composition points, the influence degree of each element on the solidification cracking index is calculated, and the optimal composition range is obtained.

[0014] After the composition is optimized, based on the Jmatpro thermodynamic calculation, a thermodynamic model is established by COMSOL software, and the size and shape of the molten pool are evaluated through thermal field simulation, and the range of additive manufacturing process parameters suitable for the improved M247 alloy is obtained. Subsequently, experimental verification is carried out. The influence of laser scanning pitch, laser power, and laser scanning speed on the forming quality of the improved MAR-M247 alloy by selective laser melting technology is analyzed by means of iterative optimization. Finally, the optimal process parameters are selected to realize the high-density forming of the improved MAR-M247 nickel-based alloy.

[0015] Beneficial effects: Compared with the prior art, the present invention has the following remarkable effects:

[0016] (1) In order to reduce the cracks generated in the additive manufacturing process of the MAR-M247 nickel-based alloy, the present invention reduces the crack sensitivity by reducing elements such as C and Al in the alloy; by controlling the laser power, scanning speed, and scanning pitch, etc., the temperature gradient of the molten pool is reduced, thereby reducing the thermal stress concentration caused by rapid solidification, and further reducing the generation of cracks, and finally realizing the additive manufacturing of the high-density MAR-M247 nickel-based alloy;

[0017] (2) Verified by experiments, in the most optimal scheme, the porosity of the improved MAR-M247 nickel-based alloy prepared by the present invention is only 0.04%, and the crack density (number of cracks / unit area) is 1.2×10 -6 (1 / μm 2 ) and the average length of the cracks is 39 μm. Brief Description of the Drawings

[0018] Figure 1 It is the metallographic diagram of the typical MAR-M247 nickel-based alloy in Comparative Example 1;

[0019] Figure 2 It is the metallographic diagram of the improved MAR-M247 nickel-based alloy with optimized composition but mismatched forming process in Comparative Example 2;

[0020] Figure 3 It is the metallographic diagram of the improved MAR-M247 nickel-based alloy with optimized composition and printing parameters in Example 1. Detailed Description of the Invention

[0021] The present invention will be further described in detail below in conjunction with the embodiments and the drawings.

[0022] Example 1: The mass percentage components of the improved MAR-M247 nickel-based alloy powder provided in this example are: Ti 1.0%, Cr 8.4%, Co 10%, W 10%, Ta 3.0%, Mo 0.7%, B 0.015%, Hf 0.005%, C 0.1%, Al 4.75%, Zr 0.025%, and the balance is Ni.

[0023] The design and preparation method of the above-mentioned improved MAR-M247 nickel-based alloy is as follows:

[0024] (1) Optimize the contents of C, Al, and Zr on the basis of the original MAR-M247: Analyze the influence rules of the change of the content of a single element in C, Al, and Zr on the equilibrium phase characteristic parameters γ' phase and carbide by thermodynamic calculation; on this basis, orthogonally design the alloy composition, and take the low solidification cracking index SCI as the calculation criterion to screen out all composition points with SCI ≤ 2000 to obtain the optimized composition range and get the composition of the improved MAR-M247 nickel-based alloy;

[0025] (2) Weigh the alloy powder according to the composition of the improved MAR-M247 nickel-based alloy obtained in step (1), and then place it in a vacuum drying oven for drying for 12 h, and the drying temperature is 80°C. Use computer software to design and generate a three-dimensional model required for the selective laser melting technology, evenly spread the dried alloy powder on a stainless steel substrate, and layer-by-layer print and form according to the constructed three-dimensional model. The printing parameters are: under a high-purity argon gas as the protective atmosphere, the scanning spacing is 0.055 mm, the laser power is 105 W, the laser scanning speed is 900 mm / s, the scanning strategy is to rotate 67° between layers, and the powder spreading thickness is 0.05 mm, so as to obtain the improved MAR-M247 nickel-based alloy.

[0026] The nickel-based alloy sample prepared in Example 1 was characterized. The density of the formed improved MAR-M247 alloy was 99.6%, and the crack density was 1.2×10 -6 (1 / μm 2 ), and the average length of the cracks was 39 μm.

[0027] Comparative Example 1: The components of the typical MAR-M247 nickel-based alloy are as follows: Ti: 1%, Cr: 8.25%, Co: 10%, W: 10%, Ta: 1.5%, Mo: 0.7%, B: 0.015%, Hf: 1.5%, C: 0.15%, Al: 5.5%, Zr: 0.05%, Fe: 0.5%, Ni: 59%.

[0028] The preparation method was as follows: A three-dimensional model required for the selective laser melting technology was designed and generated using computer software. The dried alloy powder was evenly spread on a stainless steel substrate and printed layer by layer according to the constructed three-dimensional model. The printing parameters were: under a high-purity argon protective atmosphere, the scanning spacing was 0.08 mm, the laser power was 225 W, the laser scanning speed was 1200 mm / s, the scanning strategy was to rotate 67° between layers, and the powder spreading thickness was 0.03 mm, to obtain the MAR-M247 nickel-based alloy.

[0029] Comparative Example 2: The mass percentage components of the improved MAR-M247 nickel-based alloy powder provided in this comparative example are: Ti 1.0%, Cr 8.4%, Co 10%, W 10%, Ta 3.0%, Mo 0.7%, B 0.015%, Hf 0.005%, C 0.0875%, Al 4.75%, Zr 0.02%, and the balance is Ni.

[0030] The preparation method of the above improved MAR-M247 nickel-based alloy was as follows: The alloy powder was placed in a vacuum drying oven and dried for 12 h at a drying temperature of 80 °C. A three-dimensional model required for SLM was designed and generated using computer software. The dried alloy powder was evenly spread on a stainless steel substrate and printed layer by layer according to the constructed three-dimensional model. The printing parameters were: under a high-purity argon protective atmosphere, the scanning spacing was 0.03 mm, the laser power was 125 W, the laser scanning speed was 700 mm / s, the scanning strategy was to rotate 67° between layers, and the powder spreading thickness was 0.08 mm, to obtain the improved MAR-M247 nickel-based alloy.

[0031] The nickel-based alloy sample prepared in Example 1 was characterized. The density of the formed improved MAR-M247 alloy was 99.5%, and the crack density was 2.3×10 -6 (1 / μm 2 ) and the average length of the cracks was 45 μm.

[0032] Figure 1 This is a metallographic image of the MAR-M247 nickel-based alloy formed by the selective laser melting technology in Comparative Example 1. It can be seen from the figure that there are a large number of cracks in the printed MAR-M247 alloy.

[0033] Figure 2 This is the metallographic image of the MAR-M247 nickel-based alloy after composition optimization formed by the selective laser melting technology in comparative example 2. Figure 1 In comparison, the number of cracks in the improved MAR-M247 alloy is significantly reduced, but due to the incompatibility of the forming process, more holes appear and the density is lower.

[0034] Figure 3 The metallographic diagram of the MAR-M247 nickel-based alloy after the composition and printing parameters of the selective laser melting technology in Example 1 are optimized. Figure 3 It can be seen that the alloy has excellent forming quality after composition design and process optimization, with no obvious cracks and a few holes. The density of the sample was measured by Archimedes drainage method, reaching more than 99.6%.

[0035] As can be seen from the above, the present invention reduces the content of carbides and γ' phase in the alloy by optimizing the alloy composition, thereby reducing the cracking tendency of the alloy; on the other hand, by adjusting the printing process parameters, the energy input is reduced to ensure the stability of the molten pool state and avoid excessive heat concentration, ultimately achieving additive manufacturing of high-density MAR-M247 nickel-based alloy.

Claims

1. An improved MAR-M247 nickel-based alloy suitable for additive manufacturing, characterized in that, By mass percentage, it includes the following chemical components: Ti 1.0 - 2.0%, Cr 8.4 - 10.0%, Co 9.0 - 11.0%, W 9.0 - 11.0%, Ta 3.0 - 4.0%, Mo 0.5 - 1.5%, B 0.01 - 0.03%, Hf 0.005 - 0.01%, C 0.07 - 0.11%, Al 4.5 - 5.0%, Zr 0.02 - 0.04%, and the balance is Ni.

2. The improved MAR-M247 nickel-based alloy according to claim 1, characterized in that, By mass percentage, it includes the following chemical components: Ti 1.0%, Cr 8.4 - 10.0%, Co 10%, W 10%, Ta 3.0%, Mo 0.7%, B 0.015%, Hf 0.005 - 0.01%, C 0.07 - 0.0875%, Al 4.5 - 4.75%, Zr 0.02 - 0.04%, and the balance is Ni.

3. The improved MAR-M247 nickel-based alloy according to claim 2, characterized in that, By mass percentage, it includes the following chemical components: Ti 1.0%, Cr 8.4%, Co 10%, W 10%, Ta 3.0%, Mo 0.7%, B 0.015%, Hf 0.005%, C 0.0875%, Al 4.75%, Zr 0.02 - 0.03%, and the balance is Ni.

4. A design and preparation method of the improved MAR-M247 nickel-based alloy applicable to additive manufacturing according to any one of claims 1-3, characterized in that, It includes the following steps: (1) Optimize the contents of C, Al, and Zr on the basis of the original MAR-M247: Analyze the influence law of the change of the content of a single element in C, Al, and Zr on the equilibrium phase characteristic parameters by thermodynamic calculation; on this basis, orthogonally design the alloy composition, and take the low solidification cracking index SCI as the calculation criterion to screen out all composition points with SCI ≤ 2000, obtain the optimized composition range, and get the composition of the improved MAR-M247 nickel-based alloy. (2) Optimize the additive manufacturing process of the improved MAR-M247 nickel-based alloy obtained in step (1). The optimized process parameters include: laser power, laser scanning speed, laser scanning spacing, and powder spreading thickness. Molding specimens under the optimized process parameters, and finally obtain the MAR-M247 nickel-based alloy suitable for additive manufacturing.

5. The design preparation method according to claim 3, characterized in that In step (1), the equilibrium phase characteristic parameters include γ' phase and carbide.

6. The preparation method of the design according to claim 3, characterized in that, In step (2), the laser power is 90 - 115 W.

7. The design preparation method according to claim 3, characterized in that, In step (2), the laser scanning speed is 800 - 1000 mm / s.

8. The design preparation method according to claim 3, characterized in that, In step (2), the scanning spacing is 0.03 - 0.06 mm.

9. The design preparation method according to claim 3, wherein In step (2), the powder spreading thickness is 0.03 - 0.07 mm.

10. The preparation method of the design according to claim 3, characterized in that, In step (2), the molding method is selective laser melting technology, the scanning strategy is reciprocating scanning within the layer, rotating 67° between layers, and high-purity argon is used as the shielding gas.

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