Nickel-based alloy suitable for high-temperature hydrogen environment and component design and preparation method of nickel-based alloy

Abstract

The invention discloses a nickel-based alloy suitable for a high-temperature hydrogen environment and a component design and preparation method thereof. On the basis of traditional nickel-based alloy components, the contents of Cr, Mo and C elements are reduced, and the contents of W, Mn and B elements are increased; determining the content range of gamma'phase forming elements Al and Ti in the alloy based on the weldability of the nickel-based alloy and the required high-temperature mechanical property; calculating and evaluating the tendency of the TCP harmful phase based on a d-electronic alloy theory; software JMatPro and Thermo-calc are used for calculating and designing an equilibrium phase diagram of the alloy, the precipitation amount of sigma, mu and Laves phases is particularly concerned, a Scheil solidification curve is calculated, the solidification cracking index of the alloy is further obtained, and the content of each element in the alloy is optimized. The alloy design method is simple and easy to implement, compared with a traditional nickel-based alloy Hastelloy X (GH3536), the crack forming tendency in the additive manufacturing process is reduced, the tendency of harmful TCP phase precipitation is reduced, the hydrogen-induced damage resistance is improved, and better high-temperature mechanical performance is achieved.

Description

Technical Field

[0001] The present invention relates to the field of alloy design and additive manufacturing, and in particular to a nickel-based alloy suitable for high-temperature hydrogen environments and a composition design and preparation method thereof. Background Art

[0002] Using natural gas mixed with hydrogen as fuel to supply gas turbines for power generation is beneficial to reducing carbon emissions and can also make full use of existing infrastructure such as natural gas pipelines, so it has broad application prospects. However, the hydrogen atom is the smallest atom in nature. In a high-temperature hydrogen environment, hydrogen will be adsorbed on the surface of metal parts and diffuse into the interior, causing material performance degradation (especially plasticity and toughness), leading to various types of hydrogen damage failure. In order to achieve safe and efficient mixed hydrogen combustion, the mixed hydrogen gas engine needs to change the structural design and materials of the combustion chamber nozzle.

[0003] Traditional gas turbine combustion chamber nozzles are usually made of Hastelloy X (GH3536) nickel-based alloy. This alloy has solid solution strengthening elements such as Cr, Mo, W, and Co added to the nickel matrix. Therefore, it still has high high temperature strength, creep strength, and endurance strength at temperatures of 650℃ to 900℃, good oxidation resistance, and good gas corrosion resistance. Therefore, it is widely used in gas turbines. However, the above nickel-based alloys are not specially designed for high-temperature hydrogen environments. Studies have shown that nickel-based alloys such as Hastelloy X (GH3536) are at risk of hydrogen-induced damage in hydrogen environments. Among them, carbides precipitated at the grain boundaries of nickel-based alloys accelerate the short-range diffusion of hydrogen along the grain boundaries, which in turn leads to intergranular cracking, which is an important reason for the decrease in the ability of nickel-based alloys to resist hydrogen-induced damage. In addition, due to the addition of a large amount of Cr, Mo, and W elements, Hastelloy X (GH3536) is prone to precipitate TCP phase (i.e., topologically close-packed phase) during long-term service at high temperatures, which will reduce the mechanical properties of the material and promote hydrogen-induced damage.

[0004] In terms of manufacturing process, since the combustion chamber nozzle of the hybrid hydrogen engine is designed with complex internal flow channels, it is very difficult to use traditional machining methods, and it is necessary to apply laser powder bed melting additive manufacturing technology (LPBF) to manufacture. LPBF additive manufacturing technology uses a highly focused laser beam to form a fast-moving tiny molten pool (about 200μm) on a metal powder bed, which can produce parts with complex geometry and precise structure. Due to the small molten pool, fast cooling rate and high temperature gradient, LPBF additive manufacturing technology can obtain a finer structure. However, Hastelloy X (GH3536) contains high levels of Cr, Mo, and W elements. When using the additive manufacturing process, due to the fast solidification rate of the molten pool, the above elements are easy to segregate at the grain boundaries, and the tendency to form cracks is high, making it difficult to obtain crack-free parts. Therefore, it is necessary to design and develop a new type of nickel-based alloy to replace Hastelloy X (GH3536), so that it is not easy to produce hydrogen segregation at its grain boundaries, has a stable phase structure and high-temperature mechanical properties, and is suitable for additive manufacturing processes, so that it can be better applied to high-temperature hydrogen environments.

[0005] Studies have shown that the high-temperature strength of the alloy can be significantly improved by introducing elements such as Al and Ti to precipitate an appropriate volume fraction of γ' phase (Ni3Al) in the nickel-based alloy. Controlling the content of solid solution strengthening elements such as W, Mo, Co, and Cr can inhibit the generation of TCP harmful phases and obtain a narrow solidification range, which can effectively reduce the tendency of the alloy to form cracks during solidification. Adding a small amount of B element to the nickel-based alloy can inhibit the diffusion of hydrogen atoms, and adding a small amount of V element can form carbide traps in the structure to capture free hydrogen atoms, which can effectively improve the alloy's resistance to hydrogen-induced damage. In view of this, the present invention proposes a new nickel-based alloy suitable for high-temperature hydrogen environments and a preparation method. Compared with traditional Hastelloy X (GH3536), the crack formation tendency in the additive manufacturing process is reduced, the tendency of harmful TCP phase precipitation is reduced, the resistance to hydrogen-induced damage is improved, and it has better high-temperature mechanical properties. Summary of the invention

[0006] One of the purposes of the present invention is to provide a novel nickel-based alloy composition design method suitable for high-temperature hydrogen environment. The alloy has excellent high-temperature performance and hydrogen damage resistance, and has low additive manufacturing crack sensitivity.

[0007] The second object of the present invention is to provide a method for preparing a new type of nickel-based alloy suitable for high-temperature hydrogen environment.

[0008] One of the purposes of the present invention is achieved by the following technical solution:

[0009] A new nickel-based alloy composition design method suitable for high-temperature hydrogen environment, the specific design method is as follows:

[0010] 1) Determine the types of elements contained in the nickel-based alloy according to the composition of the GH3536 alloy, reduce the content of Cr, Mo, and C elements, and increase the content of W, Mn, and B elements;

[0011] 2) Add appropriate amounts of Al and Ti elements to the alloy to form a certain mass fraction of γ' phase (Ni3Al) to strengthen the alloy, and control the content range of γ' phase according to its adverse effect on the weldability of the alloy: Al+Ti≤3.15wt%;

[0012] 3) Based on the inhibitory effect of B on the diffusion rate of hydrogen atoms and the role of V in introducing hydrogen traps, appropriate amounts of B and V are added to the alloy, and the mass percentages of both are between 0.06% and 0.07%;

[0013] 4) Based on the d-electron alloy theory, the tendency of TCP harmful phase is evaluated so that the Md of the designed nickel-based alloy is ≤ 0.93;

[0014] 5) Use thermodynamic calculation software JMatPro and Thermo-calc to calculate the equilibrium phase diagram and Scheil solidification curve of the designed alloy, pay special attention to the precipitation content of σ, μ, and Laves, and further calculate the solidification cracking index of the designed nickel-based alloy from the Scheil solidification curve. Under the precursor that meets the optimization conditions of steps 2)-4), reduce the precipitation content of σ, μ, and Laves and the solidification cracking index as much as possible, and further optimize the content of each element in the alloy.

[0015] Further, the Md of the new nickel-based alloy designed in step 4) refers to the average value of the d orbital energy Md It can be calculated by formula 1:

[0016]

[0017] Among them, x i is the atomic percentage of alloying element i, (Md) i is the Md value of alloy element i.

[0018] Furthermore, the solidification cracking index SCI (Solidification cracking index) of the designed new nickel-based alloy can be calculated by formula 2:

[0019]

[0020] Where T is temperature, f s is the solid phase fraction.

[0021] Furthermore, the composition of the novel nickel-based alloy is designed to be as follows in terms of weight percentage:

[0022] Al 1.00%~3.00%, Ti 0.05%~0.15%, Fe 15.00%~20.00%, Cr 20.00%~21.50%, Mo 2.00%~6.00%, Mn 1.50%~2.50%, Co 0.50%~1.30%, W 1.50%~2.50%, C 0.05%~0.08%, B 0.05%~0.10%, V 0.05%~0.10%, Ni balance.

[0023] Furthermore, the novel nickel-based alloy is designed to have the following components in weight percentage: Al 1.20%-1.30%, Ti 0.10%-0.12%, Fe 16%-17.5%, Cr20.5%-21.00%, Mo 5.0%-6.00%, Mn 2.0%-2.50%, Co 1.0%-1.25%, W 2.0%-2.50%, C 0.06%-0.065%, B 0.06%-0.07%, V 0.06%-0.07%, and Ni balance.

[0024] The novel nickel-based alloy component involved in the present invention is obtained by modifying the GH3536 alloy component. The specific design principle is as follows:

[0025] (1) Compared with GH3536 alloy, the content of Cr, Mo and C elements is reduced in the alloy of the present invention, and the content of W and Mn elements is increased. The reason is that the hydrogen entering the alloy is easy to combine with the free C inside the alloy, thereby accelerating the diffusion of hydrogen in the alloy. On the one hand, reducing the content of C element and on the other hand, increasing the stable carbide forming elements can effectively inhibit this phenomenon. The loss of alloy strength caused by the reduction of C element content is compensated by Mn element. Too high content of Cr or Mo element will cause more harmful phase δ phase to precipitate in the alloy, which leads to the decrease of alloy plasticity and corrosion resistance. Therefore, the amount of these two elements is appropriately reduced in the alloy of the present invention, and the weakening of solid solution strengthening effect is compensated by W element;

[0026] (2) Compared with the GH3536 alloy, more Al and Ti elements are added to the alloy of the present invention, and the content of Al element is significantly greater than that of Ti element. This is because more γ' phase (Ni3Al) needs to be precipitated in the alloy to strengthen the alloy; B element can reduce the diffusion coefficient of hydrogen in the alloy, and B atoms are easily segregated at the Ni3Al grain boundary. The competition between B and hydrogen atoms at the grain boundary reduces the effect of hydrogen atoms weakening the grain boundary. Therefore, the present invention needs to improve the alloy's resistance to hydrogen damage through the synergistic effect of B and Al elements;

[0027] (3) Excessive precipitation of γ' phase in nickel-based high-temperature alloys will affect their additive manufacturing formability, so the content of γ' phase-forming elements Al and Ti should be controlled within a reasonable range. In the present invention, Al+Ti≤3.15wt%;

[0028] (4) Introducing hydrogen traps into the alloy can effectively improve the alloy's ability to resist hydrogen penetration. Adding a small amount of V element into the alloy can form carbides that capture hydrogen atom traps in the structure, thus effectively improving the alloy's resistance to hydrogen damage;

[0029] (5) The precipitation tendency of TCP phase in the alloy is calculated by d-electron alloy theory, and the phase composition in the alloy is calculated by combining the thermodynamic software Thermo-calc to ensure that no obvious TCP phase is precipitated during the long-term aging process of the alloy at a working temperature of about 900°C.

[0030] (6) According to solidification physics, in the additive manufacturing process, when the alloy in the molten pool is about to solidify, When The smaller the value, the shorter the liquid alloy channel between the grain boundaries, the easier it is for the liquid alloy to replenish the area, and the lower the possibility of defects such as intergranular cracks and holes. Since the addition of alloying elements such as C, Cr, Mo, Al, and Ti will affect the solidification characteristics of the alloy, it is necessary to perform thermodynamic calculations and analyze the shapes of solidification curves under different alloy compositions, so as to select alloy components with lower solidification cracking sensitivity.

[0031] The second object of the present invention is achieved by the following scheme:

[0032] A method for preparing a new type of nickel-based alloy suitable for a high-temperature hydrogen environment comprises the following steps: preparing the nickel-based alloy composition according to the present invention to obtain a mixed alloy powder; performing selective laser melting additive manufacturing on the mixed alloy powder; performing solution heat treatment on the alloy printed by additive manufacturing; and performing shot peening on the alloy after the heat treatment.

[0033] Furthermore, the preparation method of the novel nickel-based alloy suitable for high-temperature hydrogen environment described in the present invention specifically comprises the following preparation steps:

[0034] The first step is to prepare alloy billets: prepare ingots that meet the composition of the designed new nickel-based alloy by arc melting;

[0035] The second step is ingot remelting: the ingot is placed in a vacuum atomization induction melting chamber and heated to above the melting point to obtain molten metal;

[0036] The third step is atomization: high-pressure argon gas is used to break the molten metal into tiny particles, which are then condensed into metal powder.

[0037] Step 4: Screening powder: Screen out finished powder with a particle size of 17-53μm;

[0038] Step 5: Forming: Adjust the parameters of the selective laser melting process to print the designed new nickel-based alloy;

[0039] Step 6: performing solution heat treatment on the alloy printed in step 5;

[0040] In the seventh step, the alloy after the heat treatment in the sixth step is shot peened.

[0041] Furthermore, the solution treatment temperature was set to 1200°C, the holding time was 1h, and the cooling method was water quenching.

[0042] Furthermore, the shot peening pressure used in the shot peening process is less than 0.35 MPa.

[0043] The solution heat treatment in the preparation method of the present invention can eliminate needle-shaped harmful phases such as δ and σ in the alloy, reduce the precipitation of strengthening phases γ' and γ", and will not dissolve the carbides formed by adding V element, so the structure is more uniform, the comprehensive performance is better, and the hydrogen damage resistance is also strong; the shot peening treatment can refine the grains of the surface layer of the alloy, create more dislocations on the surface of the alloy, and after hydrogen enters the alloy, it is first attracted by the surface layer dislocations, so the hydrogen entering the alloy is greatly reduced, so the hydrogen damage resistance of the alloy is improved.

[0044] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0045] Adding trace amounts of B elements to nickel-based alloys is expected to synergistically improve the grain boundary strength of the alloy with the Al element in the alloy; adding trace amounts of V elements to the alloy can weaken the diffusion of hydrogen in the alloy; reducing the content of Cr and Mo elements can effectively inhibit the precipitation of σ phase and further improve the corrosion resistance of the alloy; setting up solid solution annealing heat treatment can dissolve the δ phase as well as the γ' and γ" phases in the alloy, further reducing the hydrogen embrittlement sensitivity of the alloy; shot peening the alloy after heat treatment can refine the surface grains and introduce a large number of dislocations in the alloy surface, further inhibiting the entry of hydrogen into the alloy.

[0046] In summary, the present invention adopts a variety of ways to suppress the hydrogen damage mechanism of nickel-based alloys to design alloy composition and preparation method, and combines the characteristics of additive manufacturing technology, through d-electronic alloy design theoretical calculation and Thermo-calc software simulation analysis and evaluation, it is expected to achieve the reduction or even elimination of cracks in the additive manufacturing process and the improvement of material mechanical properties and hydrogen damage resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 The phase diagram of the alloy designed in Example 1 of the present invention calculated by JMatPro;

[0048] Figure 2 It is a partial enlargement of the phase diagram of the alloy designed in Example 1 of the present invention calculated by Thermo-calc;

[0049] Figure 3 The yield strength of the alloy designed in Example 1 of the present invention and the conventional GH3536 alloy at high temperature calculated by JMatPro;

[0050] Figure 4 The cracking factor calculated according to the Scheil solidification path of the alloy designed in Example 1 of the present invention and the conventional GH3536 alloy varies with the solid phase fraction;

[0051] Figure 5 Schematic diagram of the shot peening structure strengthening effect of the alloy designed in Example 1 of the present invention. DETAILED DESCRIPTION

[0052] In order to more clearly illustrate the specific implementation of the present invention or the technical solution in the prior art, the drawings required for use in the specific implementation or the description of the prior art are briefly introduced below.

[0053] Example 1

[0054] In a specific implementation process, the present invention provides a novel nickel-based alloy composition design and preparation method suitable for high-temperature hydrogen environment.

[0055] The design method of new nickel-based alloy composition suitable for high-temperature hydrogen environment is as follows:

[0056] The first step is to determine the types of elements contained in the nickel-based alloy according to the composition of the GH3536 alloy, introduce V into the alloy, reduce the content of Cr, Mo, and C elements, and increase the content of W, Mn, and B elements;

[0057] The second step is to determine the content range of γ' phase forming elements Al and Ti in the alloy based on the weldability of the nickel-based high-temperature alloy to meet the following conditions: Al+Ti≤3.15wt%, wherein the mass percentage of Al element is 1.25wt%, and the mass percentage of Ti element is 0.1wt%;

[0058] The third step is to roughly determine the content range of B and V elements based on the inhibitory effect of B element on the diffusion rate of hydrogen atoms and the effect of V element introducing hydrogen traps, where the mass percentage of B element is 0.06wt% and the mass percentage of V element is 0.06wt%;

[0059] The fourth step is to evaluate the tendency of TCP harmful phase based on d-electron alloy theory calculation, so that the Md of the designed nickel-based alloy is ≤ 0.93, and the content of other elements is roughly determined;

[0060] The fifth step is to use the thermodynamic calculation software JMatPro and Thermo-calc to calculate the equilibrium phase diagram and Scheil solidification curve of the designed alloy, with special attention paid to the precipitation content of σ, μ, and Laves. The solidification cracking index of the designed nickel-based alloy is further calculated from the Scheil solidification curve. Under the premise of meeting the optimization conditions of the second to fourth steps, the precipitation content of σ, μ, and Laves and the solidification cracking index are reduced as much as possible to further optimize the content of each element in the alloy.

[0061] The composition of the novel nickel-based alloy designed in Example 1 of the present invention is as follows in terms of weight percentage: Al 1.25%, Ti 0.10%, Fe 17.5%, Cr 21.00%, Mo 6.00%, Mn 2.50%, Co 1.25%, W 2.50%, C 0.06%, B 0.06%, V 0.06%, and Ni balance. The Md value of the alloy is calculated based on the d-electron theory to be about 0.71, which is in line with the design expectation.

[0062] The preparation method of the nickel-based alloy in Example 1 of the present invention is as follows:

[0063] The first step is to prepare alloy billets: prepare ingots that meet the composition of the designed new nickel-based alloy by arc melting;

[0064] The second step is ingot remelting: the ingot is placed in a vacuum atomization induction melting chamber and heated to above the melting point to obtain molten metal;

[0065] The third step is atomization: high-pressure argon gas is used to break the molten metal into tiny particles, which are then condensed into metal powder.

[0066] Step 4: Screening powder: Screen out finished powder with a particle size of 17-53μm;

[0067] Step 5: Forming: Set the selective laser melting forming parameters to print the designed new nickel-based alloy, where the laser power is 300 W, the scanning speed is 850 mm / s, the scanning interval is 81 μm, the layer thickness is 40 μm, and the spot diameter is 60 μm.

[0068] Step 6: Perform solution heat treatment on the alloy printed in step 5, setting the solution temperature to 1200°C, the holding time to 1h, and the cooling method to water quenching;

[0069] Step 7: Shot peening the alloy after the heat treatment in step 6, with the shot peening pressure set to 0.30 MPa. Figure 5 As shown, it can be seen that the surface grains are refined, forming a compressive stress state, and having better fatigue resistance.

[0070] The phase diagram of the new nickel-based alloy suitable for high-temperature hydrogen environment designed in Example 1 of the present invention is calculated using JMatPro. The results are as follows: Figure 1 shown. Figure 1 Thermo-calc calculation of the phase diagram shown in the partial enlargement (phase composition 0 ~ 5% interval) see Figure 2 shown.

[0071] In addition, taking the existing conventional GH3536 alloy as a control, the composition of the conventional GH3536 alloy in terms of weight percentage is as follows: Al 0.03%, Ti 0.008%, Fe 19.14%, Cr21.73%, Mo 8.73%, Mn 0.008%, Co1.56%, W 0.77%, C 0.08%, B0.002%, and Ni balance.

[0072] The alloy designed in Example 1 of the present invention and the conventional GH3536 alloy are compared. The cracking factor of the two alloys calculated according to the Scheil solidification path varies with the solid phase fraction. Figure 4 The comparison of yield strength of the two at high temperature calculated by JMatPro can be found in Figure 3 .

[0073] according to Figure 3-Figure 4 As a result, the solidification cracking index of the alloy designed in Example 1 in the solid phase fraction range of 0.91 to 0.97 is smaller than that of the GH3536 alloy, and the yield strength in a high temperature environment of 650 to 900°C is higher than that of the GH3536 alloy. Therefore, it is believed that the stability of the additive manufacturing forming process and the product quality can be greatly improved through the composition optimization of the present invention.

[0074] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A nickel-based alloy suitable for high-temperature hydrogen environment, characterized in that Calculated by weight, it is composed of the following components: Al 1.00%-3.00%, Ti 0.05%-0.15%, Fe 15.00%-20.00%, Cr 20.00%-21.50%, Mo 2.00%-6.00%, Mn 1.50%-2.50%, Co 0.50%-1.30%, W 1.50%-2.50%, C 0.05%-0.08%, B 0.05%-0.10%, V 0.05%-0.10%, and Ni balance.

2. A nickel-based alloy suitable for high temperature hydrogen environment as claimed in claim 1, characterized in that Calculated by weight, it is composed of the following components: Al 1.20%~1.30%, Ti 0.10%~0.12%, Fe 16%~17.5%, Cr20.5%~21.00%, Mo 5.0%~6.00%, Mn 2.0%~2.50%, Co 1.0%~1.25%, W 2.0%~2.50%, C 0.06%~0.065%, B 0.06%~0.07%, V 0.06%~0.07%, and Ni balance.

3. A nickel-based alloy suitable for high-temperature hydrogen environment, characterized in that The nickel-based alloy composition as described in claim 1 or 2 is formulated to obtain a mixed alloy powder; the mixed alloy powder is subjected to selective laser melting additive manufacturing; the alloy printed by additive manufacturing is subjected to solution heat treatment; and the alloy after the heat treatment is subjected to shot peening.

4. A method for designing nickel-based alloy composition suitable for high-temperature hydrogen environment, characterized in that: The following steps are involved: 1) Determine the types of elements contained in the nickel-based alloy according to the composition of the GH3536 alloy, reduce the content of Cr, Mo, and C elements, and increase the content of W, Mn, and B elements; 2) Add appropriate amounts of Al and Ti elements to the alloy to form a certain mass fraction of γ' phase (Ni3Al) to strengthen the alloy, and control the content range of γ' phase according to its influence on the weldability of the alloy: Al+Ti≤3.15wt%; 3) Based on the inhibitory effect of B on the diffusion rate of hydrogen atoms and the role of V in introducing hydrogen traps, appropriate amounts of B and V are added to the alloy, and the mass percentages of both are between 0.06% and 0.07%; 4) Based on the d-electron alloy theory, the tendency of TCP harmful phase is evaluated so that the Md of the designed nickel-based alloy is ≤ 0.93; 5) Use thermodynamic calculation software JMatPro and Thermo-calc to calculate the equilibrium phase diagram and Scheil solidification curve of the designed alloy, pay special attention to the precipitation content of σ, μ, and Laves, and further calculate the solidification cracking index of the designed nickel-based alloy from the Scheil solidification curve. Under the precursor that meets the optimization conditions of steps 2)-4), reduce the precipitation content of σ, μ, and Laves and the solidification cracking index as much as possible, and further optimize the content of each element in the alloy.

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