High-strength nickel-based alloy suitable for additive manufacturing and design and preparation method of high-strength nickel-based alloy

Abstract

The invention discloses a high-strength nickel-based alloy suitable for additive manufacturing and a design and preparation method of the high-strength nickel-based alloy, and belongs to the field of alloy materials. The high-strength nickel-based alloy is prepared from the following components in percentage by mass: 17 to 20 weight percent of Co, 11 to 14 weight percent of Cr, 1 to 3 weight percent of Mo, 6 to 8 weight percent of W, 1 to 2 weight percent of Al, 2.5 to 3.5 weight percent of Ti, 0.3 to 1.2 weight percent of Nb, 0.6 to 1.5 weight percent of Ta, 0.01 to 0.1 weight percent of C, 0 to 0.1 weight percent of B and the balance of Ni, the design and preparation method comprises the following steps: (1) designing nickel-based alloy components; (2) preparing a nickel-based alloy through a laser powder bed fusion technology, determining a VED (Volume Energy Density) determination process window based on the volume energy density, and obtaining a nickel-based alloy part; and (3) the nickel-based alloy part is subjected to solid solution heat treatment and two-step aging treatment. The nickel-based alloy is particularly suitable for manufacturing precise and complex hot-end high-temperature components in the fields of aerospace, energy, chemical industry and the like.

Description

Technical Field

[0001] The present invention belongs to the field of alloy materials, and particularly relates to a high-strength nickel-based alloy suitable for additive manufacturing and a design and preparation method thereof. Background Art

[0002] Nickel-based superalloys have excellent high-temperature strength, high-temperature corrosion resistance, and creep resistance, and still have good stability under harsh environments such as high temperature and high pressure. They are widely used in the manufacture of hot-end components in aerospace, energy chemical engineering, nuclear engineering, etc. Especially in the aspect of high-temperature blades, they are one of the most precise and complex parts in aeroengines, and their shape and dimensional accuracy have a direct impact on the performance of the engine. The traditional preparation methods of nickel-based superalloys mainly include casting, forging, etc. These methods have problems such as low manufacturing accuracy and high production costs.

[0003] As an emerging manufacturing technology, additive manufacturing technology has the advantages of high processing accuracy, short manufacturing cycle, high material utilization rate, etc., and provides a new way for the preparation of nickel-based superalloys. However, most of the nickel-based superalloys currently applied to additive manufacturing are designed for traditional manufacturing processes, so some high-performance alloys cannot meet the special requirements of additive manufacturing. During the additive manufacturing process of nickel-based superalloys, the appearance of defects such as cracks and pores seriously affects the quality and performance of the alloy. Usually, weldability is used as the evaluation standard for the forming quality of the alloy. Common weldable alloys include Inconel 718, Inconel 625, etc. Such alloys are mainly strengthened by the γ'' phase, and the γ'' phase is a metastable phase. When the alloy is under long-term service conditions at 650 °C and higher temperatures, the γ'' phase, which is the main precipitation strengthening phase of the alloy, will coarsen and transform into the stable δ phase, resulting in a decrease in the mechanical properties of the alloy. Common non-weldable alloys include Inconel 939, MAR-M247, etc. Such alloys use the γ' phase as the main strengthening phase, and the cracking sensitivity of the alloy increases with the increase in the content of the γ' phase. It can be seen that there is a contradiction between the weldability and mechanical properties of nickel-based superalloys. Nickel-based superalloys with a low γ' phase content can achieve crack-free preparation, but cannot meet the application requirements of high strength and high-temperature stability.

[0004] Related research shows that the high crack sensitivity of nickel-based superalloys with a high γ' phase content can be reduced by means such as composition modification, addition of a second phase, or optimization of process parameters, but the crack problem cannot be solved at the root. Therefore, in order to balance the weldability and high-temperature performance of the alloy, it is necessary to develop a high-strength γ' phase precipitation-strengthened nickel-based alloy suitable for additive manufacturing and optimize the preparation process. Summary of the Invention

[0005] Object of the Invention: To solve the problem of high crack sensitivity of nickel-based superalloys with high γ'-phase content in the prior art, the first object of the present invention is to provide a high-strength nickel-based alloy that takes into account weldability and mechanical properties, and the second object of the present invention is to provide a design and preparation method for the above high-strength nickel-based alloy.

[0006] Technical Solution: The high-strength nickel-based alloy suitable for additive manufacturing provided by the present invention, by mass percentage, comprises the following components: Co 17-20 wt%, Cr 11-14 wt%, Mo 1-3 wt%, W 6-8 wt%, Al 1-2 wt%, Ti 2.5-3.5 wt%, Nb 0.3-1.2 wt%, Ta 0.6-1.5 wt%, C 0.01-0.1 wt%, B 0-0.1 wt%, and the balance is Ni.

[0007] Preferably, the high-strength nickel-based alloy, by mass percentage, comprises the following components: Co 18.11 wt%, Cr 13.03 wt%, Mo 2.07 wt%, W 7.31 wt%, Al 1.47 wt%, Ti 2.99 wt%, Nb 0.55 wt%, Ta 0.95 wt%, C 0.041 wt%, B 0.0064 wt%, and the balance is Ni. The yield strength at room temperature is 1100-1200 MPa, the tensile strength is 1400-1500 MPa, the yield strength at 650 °C is 950-1000 MPa, and the tensile strength is 1200-1250 MPa.

[0008] The design and preparation method for the above high-strength nickel-based alloy comprises the following steps:

[0009] (1) Design the composition of the nickel-based alloy: Using Co, Cr, Mo, W, Al, Ti, Nb, Ta, C, B and Ni as the components of the nickel-based alloy, by performing thermodynamic calculations on the main elements affecting alloy cracking and the precipitation amount of harmful phases, the relationship among composition - cracking tendency - precipitation amount of harmful phases is established. Finally, with the design criterion of reducing the alloy cracking tendency and avoiding the precipitation of harmful phases, the preferred composition range of the nickel-based alloy is obtained;

[0010] (2) Prepare the nickel-based alloy by laser powder bed fusion technology. Based on the volume energy density, determine the VED to determine the process window, and obtain nickel-based alloy parts without cracks and with low porosity;

[0011] (3) Perform solution heat treatment and two-step aging treatment on the nickel-based alloy parts to obtain a high-strength nickel-based alloy suitable for additive manufacturing.

[0012] Further, in step (1), a solidification cracking prediction model is established to constrain the contents of Cr, Mo, and W; a strain aging cracking prediction model is established to constrain the contents of Al, Ti, Nb, and Ta; a harmful phase precipitation amount prediction model is established to constrain the contents of Cr, Mo, Nb, and Ta; by constraining the contents of the above elements, solidification cracking, strain aging cracking, and harmful precipitation are avoided, and then a preferred composition range is obtained.

[0013] Further, in step (2), in the laser powder bed fusion technology, the printing strategy is reciprocating scanning within a layer, and the interlayer rotation angle is 67°; the volume energy density VED is 70 - 90 J / mm 3 .

[0014] Further, the parameters of the process window are: powder layer thickness 0.02 - 0.04 mm, laser power 110 - 130 W, laser scanning speed 750 - 1125 mm / s, and laser scanning spacing 0.045 - 0.065 mm.

[0015] Further, in step (3), the parameters of the solution heat treatment are: heat treatment at 1000 - 1100 °C for 2 - 2.5 h; the parameters of the two-step aging heat treatment are: first aging treatment at 800 - 900 °C for 4 - 4.5 h, and then aging treatment at 700 - 800 °C for 16 - 18 h.

[0016] Principle of the invention: In the nickel-based alloy of the present invention, Cr, Mo, and W segregate in the final stage of alloy solidification, causing an increase in the solidification temperature range and prone to solidification cracks. The contents of Al, Ti, Nb, and Ta directly determine the precipitation amount of the γ' strengthening phase, and excessive precipitation of the γ' phase is prone to strain aging cracks. In addition, excessive Cr promotes the precipitation of the α-Cr phase, excessive Mo promotes the precipitation of the μ phase, excessive Nb promotes the precipitation of the γ'' phase, and excessive Ta promotes the precipitation of the η phase. The precipitation of these harmful phases leads to the deterioration of the alloy properties. Through thermodynamic calculations of the main elements affecting alloy cracking and harmful phase precipitation amount, the present invention establishes the relationship among composition - cracking tendency - harmful phase precipitation amount, and finally, with the design criterion of reducing the alloy cracking tendency and avoiding harmful phase precipitation, a preferred alloy composition range is obtained.

[0017] Too low energy input will lead to insufficient energy inside the molten pool, causing the metal powder not to melt completely and forming pores, while too high energy input will lead to the instability of the molten pool and form pores. The volume energy density VED, a composite parameter, is used to represent the energy input, and its formula is as follows:

[0018]

[0019] Where L is the powder layer thickness, P is the laser power, V is the laser scanning speed, and D is the laser scanning spacing. First, study the influence of the change of a single parameter on the alloy forming quality, determine the process parameter range with good sample forming, obtain the volume energy density of different parameter combinations, and further optimize it at an appropriate volume energy density to obtain the preferred process parameter range. A nickel-based alloy with no cracks and low porosity is formed within the preferred process parameter range and heat-treated to prepare a high-strength nickel-based alloy suitable for additive manufacturing.

[0020] Beneficial effects: Compared with the prior art, the present invention has the following remarkable effects: The present invention obtains the composition of a weldable nickel-based superalloy through thermodynamic calculations, and verifies that the alloy has excellent weldability through process parameter optimization. Compared with common weldable alloys such as Inconel 718 and Inconel 625, this alloy has more excellent performance. Description of the Drawings

[0021] Figure 1 CT diagrams of the nickel-based alloy (a) and MAR-M247 (b) prepared in Example 1;

[0022] Figure 2 SEM diagram of the as-deposited nickel-based alloy prepared in Example 1;

[0023] Figure 3 SEM diagram of the heat-treated nickel-based alloy prepared in Example 1;

[0024] Figure 4 Yield strength and tensile strength diagrams of the nickel-based alloy prepared in Example 1 at 25°C and 650°C;

[0025] Figure 5 Metallographic diagrams of the nickel-based alloys prepared in Example 1 (a) and Comparative Example 1 (b). Detailed Description of the Invention

[0026] The present invention will be further described in detail below with reference to the examples and the drawings.

[0027] Example 1: The high-strength nickel-based alloy provided in this example, by mass percentage, includes the following components: Co 18.11 wt%, Cr 13.03 wt%, Mo 2.07 wt%, W 7.31 wt%, Al 1.47 wt%, Ti 2.99 wt%, Nb 0.55 wt%, Ta 0.95 wt%, C 0.041 wt%, B 0.0064 wt%, and the balance is Ni.

[0028] The preparation method of the above nickel-based alloy includes the following steps:

[0029] (1) The preparation process is laser powder bed fusion, the printing strategy is reciprocating scanning within a layer, and a 67° rotation between layers. Further optimization is based on the volume energy density (VED), and the optimal process parameters obtained are a powder layer thickness of 0.03 mm, a laser power of 120 W, a laser scanning speed of 830 mm / s, a laser scanning spacing of 0.06 mm, and a volume energy density of 80.3 J / mm 3 , and specimens are formed under these process parameters;

[0030] (2) The above-formed specimens are heat-treated. The specific heat treatment process is solution treatment (1050°C / 2 h) + two-step aging (850°C / 4 h + 760°C / 16 h), and air cooling is used in both cases.

[0031] Comparative Example 1: The difference from Example 1 is that the process parameters in step (1) are: a powder layer thickness of 0.03 mm, a laser power of 100 W, a laser scanning speed of 1200 mm / s, a laser scanning spacing of 0.07 mm, and a volume energy density of 39.7 J / mm 3 .

[0032] Figure 1 (a) in is the CT image of the nickel-based alloy prepared in Example 1. No cracks are seen, and there are a few pores, which are mainly inevitable air holes during the additive manufacturing process. Figure 1 (b) in is a typical difficult-to-weld alloy MAR-M247, with a large number of cracks, and the pore size is significantly larger than that of the nickel-based alloy in Example 1.

[0033] Figure 2 is the SEM photo of the as-deposited nickel-based alloy prepared in Example 1. It can be seen from the figure that the substrate structure of the nickel-based alloy is mainly divided into slender needle-like structures and fine cellular structures.

[0034] Figure 3 is the SEM photo of the heat-treated nickel-based alloy prepared in Example 1. It can be seen from the figure that a large number of γ' phases precipitate from the matrix.

[0035] Figure 4 are the strengths of the nickel-based alloy prepared in Example 1 after heat treatment at room temperature and 650°C. It can be seen that the nickel-based alloy prepared in Example 1 has excellent strength. Among them, the yield strength at room temperature is 1130 MPa, and the tensile strength is 1402 MPa; the yield strength at 650°C high temperature is 989 MPa, and the tensile strength is 1220 MPa.

[0036] Figure 5 (a) in is the sample prepared with the process parameters in Example 1, with a powder layer thickness of 0.03 mm, a laser power of 120 W, a laser scanning speed of 830 mm / s, a laser scanning spacing of 0.06 mm, and a volume energy density of 80.3 J / mm 3。The sample was well formed without cracks, only with a small amount of pores. Figure 5 In (b) is the sample prepared with inappropriate process parameters in Comparative Example 1, with a powder layer thickness of 0.03 mm, a laser power of 100 W, a laser scanning speed of 1200 mm / s, a laser scanning spacing of 0.07 mm, and a volume energy density of 39.7 J / mm 3 。Due to the lower volume energy density, a large number of unfused hole defects appeared in the sample.

Claims

1. A high-strength nickel-based alloy suitable for additive manufacturing, characterized in that, By mass percentage, it includes the following components: Co 17 - 20wt%, Cr 11 - 14wt%, Mo 1 - 3wt%, W 6 - 8wt%, Al 1 - 2wt%, Ti 2.5 - 3.5wt%, Nb 0.3 - 1.2wt%, Ta 0.6 - 1.5wt%, C 0.01 - 0.1wt%, B 0 - 0.1wt%, and the balance is Ni.

2. The high-strength nickel-based alloy according to claim 1, wherein By mass percentage, it includes the following components: Co 18.11wt%, Cr 13.03wt%, Mo 2.07wt%, W 7.31wt%, Al 1.47wt%, Ti 2.99wt%, Nb 0.55wt%, Ta 0.95wt%, C 0.041wt%, B 0.0064wt%, and the balance is Ni.

3. The high-strength nickel-based alloy according to claim 2, characterized in that, The yield strength of the nickel-based alloy at room temperature is 1100 - 1200 MPa, and the tensile strength is 1400 - 1500 MPa.

4. The high-strength nickel-based alloy according to claim 2, characterized in that, The yield strength of the nickel-based alloy at 650 °C is 950 - 1000 MPa, and the tensile strength is 1200 - 1250 MPa.

5. A method for designing and preparing a high-strength nickel-based alloy according to any one of claims 1-4, characterized in that, It includes the following steps: (1) Design the composition of the nickel-based alloy: Using Co, Cr, Mo, W, Al, Ti, Nb, Ta, C, B, and Ni as the components of the nickel-based alloy, through thermodynamic calculations of the main elements affecting alloy cracking and the precipitation amount of harmful phases, the relationship among composition - cracking tendency - precipitation amount of harmful phases is established. Finally, with the design criterion of reducing the alloy cracking tendency and avoiding the precipitation of harmful phases, the preferred composition range of the nickel-based alloy is obtained; (2) Prepare the nickel-based alloy by laser powder bed fusion technology. Determine the process window based on the volume energy density (VED) to obtain nickel-based alloy parts without cracks and with low porosity; (3) Subject the nickel-based alloy parts to solution heat treatment and two-step aging treatment to produce a high-strength nickel-based alloy suitable for additive manufacturing.

6. The preparation method according to claim 5, characterized in that In step (1), establish a solidification cracking prediction model to constrain the contents of Cr, Mo, and W; establish a strain aging cracking prediction model to constrain the contents of Al, Ti, Nb, and Ta; establish a harmful phase precipitation amount prediction model to constrain the contents of Cr, Mo, Nb, and Ta; by constraining the contents of the above elements, it is used to avoid solidification cracking, strain aging cracking, and harmful precipitation, and then the preferred composition range is obtained.

7. The preparation method according to claim 5, characterized in that, In step (2), in the laser powder bed fusion technology, the printing strategy is reciprocating scanning within a layer, and the interlayer rotation angle is 67°; the volume energy density VED is 70 - 90 J / mm 3 .

8. The preparation method according to claim 7, characterized in that, The parameters of the process window are: powder layer thickness 0.02 - 0.04 mm, laser power 110 - 130 W, laser scanning speed 750 - 1125 mm / s, laser scanning spacing 0.045 - 0.065 mm.

9. The preparation method according to claim 5, characterized in that, In step (3), the parameters of the solution heat treatment are: heat treatment at 1000 - 1100 °C for 2 - 2.5 h.

10. The preparation method according to claim 5, characterized in that, In step (3), the parameters of the two-step aging heat treatment are: first age at 800 - 900 °C for 4 - 4.5 h, and then age at 700 - 800 °C for 16 - 18 h.

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