A heat treatment method for improving high-temperature creep properties of laser additive manufacturing solid solution strengthening type high-temperature alloy

Abstract

The application discloses a heat treatment method for improving high-temperature creep performance of laser additive manufacturing solid solution strengthening type high-temperature alloy, and belongs to the technical field of high-temperature alloy material preparation. The application is directed to laser additive manufacturing solid solution strengthening type high-temperature alloy, and by introducing medium-temperature aging treatment after high-temperature solid solution treatment, the best matching of grain size and grain boundary pinning phase form and distribution is obtained, and the high-temperature creep performance is improved. The additive manufacturing solid solution strengthening type high-temperature alloy obtained by the heat treatment process has relatively large grain size, and the grain boundary is uniformly distributed with spherical M6C carbide. In the high-temperature deformation process, the M6C carbide can produce significant pinning effect on the grain boundary, so that the alloy has good high-temperature creep performance, and is an effective means to realize performance optimization of the additive manufacturing solid solution strengthening type high-temperature alloy.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature alloy material preparation technology, specifically a heat treatment method for improving the high-temperature creep performance of laser additive manufacturing solid solution strengthened high-temperature alloys. Background Technology

[0002] Nickel-based superalloys are widely used in the aerospace and nuclear power industries due to their excellent high-temperature microstructure and mechanical stability, good creep and fatigue properties, and outstanding oxidation and corrosion resistance. To date, superalloys remain irreplaceable key high-temperature structural materials for the four major hot-end components of advanced aero-engines and ground-based gas turbines: turbine blades, guide vanes, turbine disks, and combustion chambers. Statistics show that nickel-based superalloys account for 40%-60% of the total weight of aero-engines. Superalloys can be classified into precipitation-strengthened and solid-solution-strengthened types based on their strengthening methods. Solid-solution-strengthened superalloys, due to their lower content of precious elements and lower cost and density, are used in critical components such as fuel nozzles.

[0003] In recent years, with the rapid development of the aerospace industry, the demand for high-thrust and high thrust-to-weight ratio engines has become urgent. Achieving these goals requires continuously increasing turbine inlet temperature to maximize gas turbine efficiency. This can be achieved through two main methods: developing high-performance, lower-density alloys, and applying new technologies such as additive manufacturing to create more ingenious, lighter, and more efficient component structures. Additive manufacturing, as one of the disruptive technologies of the intelligent manufacturing era, allows for the creation of components from three-dimensional models through layer-by-layer stacking, offering significant design freedom and a natural advantage in fabricating complex components such as fuel nozzles. However, because additively manufactured components are near-net-shape, their mechanical properties are not easily improved through traditional plastic deformation. Therefore, subsequent heat treatment becomes the primary method for controlling their mechanical behavior. Additive manufacturing technologies can be categorized based on energy sources and processes, including selective laser melting (SLM), laser energy deposition (LAD), electron beam powder bed technology, and arc wire additive manufacturing. Among these, selective laser melting is widely used in various fields due to its high manufacturing precision.

[0004] Laser additive manufacturing has a cooling rate far exceeding that of traditional technologies (up to 10). 6 K / s), alloy precipitates (such as M) 23 The formation of C6, M6C, μ, etc., is significantly suppressed. Therefore, solid solution strengthened high-temperature alloys are composed of single-phase austenite with small grain size and no pinned phases at grain boundaries, which leads to poor high-temperature creep performance and makes it difficult to meet the actual service requirements. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a heat treatment method to improve the high-temperature creep performance of laser additive manufacturing solid solution strengthened high-temperature alloys, so as to solve the technical problem that the existing solid solution strengthened high-temperature alloys have poor high-temperature creep performance and cannot meet the service requirements.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] This invention discloses a heat treatment method for improving the high-temperature creep performance of laser additive manufacturing solid solution strengthened high-temperature alloys, comprising the following steps:

[0008] 1) Selective laser melting printing: Pre-alloyed powder with a particle size of 15-55 μm is prepared from solid solution strengthened high-temperature alloy, and printed alloy blocks are obtained by selective laser melting printing in a vacuum environment;

[0009] 2) High-temperature solution treatment: Heat the printed alloy block to 1075℃~1200℃, hold for 10~60 minutes, and air cool to room temperature;

[0010] 3) Medium-temperature aging treatment: The alloy block after high-temperature solution treatment is heated to 940℃~980℃, held for 2~4 hours, and then air-cooled to room temperature to complete the improvement of the high-temperature creep performance of the alloy.

[0011] Preferably, the solid solution strengthened high-temperature alloy is a solid solution strengthened high-temperature nickel-based alloy, comprising, by mass percentage: Cr 19%–23%, Fe 18%–20%, Mo 8%–10%, Co 1%–2%, Si≤1%, Mn≤1%, C≤0.09%, S≤0.01%, P≤0.01%, O≤0.02%, with the remainder being Ni.

[0012] More preferably, this invention is also applicable in principle to other high-temperature alloys with different compositions, mainly depending on whether the other alloys contain M6C-forming elements (such as Mo and W). The formation of M6C carbides requires meeting the "M6C rule," that is, M6C carbides can only form when the Mo content exceeds 6-8 wt.% or the equivalent W content exceeds 4 at.%. In other words, if other alloys also contain M6C-forming elements, this method should also be able to precipitate pinned phases at grain boundaries.

[0013] Preferably, the average grain size of the solid solution strengthened superalloy after final treatment is no greater than 40 micrometers.

[0014] Preferably, the solid solution strengthened high-temperature alloy after final treatment has a single-phase austenitic structure within the grains and obtains a uniformly distributed, discontinuously distributed spherical M6C phase at the grain boundaries.

[0015] More preferably, the average size of the M6C phase at the grain boundary is not greater than 4 μm, the area fraction is not less than 0.3%, and it is uniformly spherically distributed at the grain boundary.

[0016] Preferably, the solid solution strengthened high-temperature alloy after final treatment has a life of not less than 90 hours under creep conditions of 850℃ / 60MPa.

[0017] More preferably, the solid solution strengthened high-temperature alloy after final treatment has a creep life of 90 to 145 hours under creep conditions of 850℃ / 60MPa.

[0018] Preferably, in step 1), a selective laser melting printer is used to prepare the printed alloy block.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] This invention targets laser additive manufacturing of solid solution-strengthened superalloys. By introducing a medium-temperature aging treatment after high-temperature solution treatment, it achieves an optimal match between grain size and the morphology and distribution of pinned phases at grain boundaries, thereby improving the high-temperature creep performance. The macroscopic microstructure of the laser additive manufacturing solid solution-strengthened superalloy in its printed state consists of fine grains, while the microstructure consists of single-phase austenite. The purpose of the high-temperature solution treatment in this invention is to obtain an appropriate grain size. As the solution temperature or time increases, the grain size gradually increases. A larger grain size has a certain effect on improving the high-temperature creep performance of the alloy. However, excessively high temperatures or holding times can lead to excessively large grain sizes and oxidation of grain boundaries, which will impair the creep performance of the alloy. Therefore, the solution heat treatment specified in this invention is 1075℃-1200℃, with a holding time of 10-60 minutes, which can effectively control the grain size within a beneficial range. In addition, considering that grain boundaries are weak points in the long-term high-temperature service of the alloy, to improve the high-temperature creep performance of the alloy, it is necessary to form well-distributed pinned phases at the grain boundaries. Generally, spherical and discontinuously distributed precipitation has a better effect on grain boundary strengthening. Therefore, this invention determines that the aging process for additive manufacturing solid solution strengthened high-temperature alloys is 940℃-980℃, with a holding time of 2-4 hours. This allows M6C carbides to be distributed in a spherical and discontinuous form at the grain boundaries, thereby maximizing the high-temperature creep performance of the alloy.

[0021] The additively manufactured solid solution-strengthened superalloy obtained by the heat treatment process employed in this invention has a relatively large grain size and uniformly distributed spherical M6C carbides at the grain boundaries. During high-temperature deformation, the M6C carbides can exert a significant pinning effect on the grain boundaries, thereby giving the alloy good high-temperature creep properties. This is an effective means to optimize the performance of additively manufactured solid solution-strengthened superalloys. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the heat treatment process of the present invention;

[0023] Figure 2 This is a printed macroscopic microstructure image of the additive manufacturing solid solution strengthened high-temperature alloy described in this invention.

[0024] Figure 3 The grain configuration (a) and grain boundary M6C carbides (b) of the additive manufacturing solid solution strengthened high-temperature alloy described in this invention after high-temperature solid solution and aging treatment. Detailed Implementation

[0025] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0026] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0027] The present invention will now be described in further detail with reference to the accompanying drawings:

[0028] Example 1

[0029] Solid solution strengthened high-temperature alloy pre-alloyed powder was prepared with the following composition by weight percentage: Cr 19%-23%, Fe 18%-20%, Mo 8%-10%, Co 1%-2%, Si≤1%, Mn≤1%, C≤0.09%, S≤0.01%, P≤0.01%, O≤0.02%, with the remainder being Ni. Pre-alloyed powder with a particle size of 15-55 μm was prepared according to the above composition, and printed alloy blocks were obtained using a selective laser melting printer in a vacuum environment. The printed alloy blocks were subjected to high-temperature solid solution treatment at 1200℃ for 60 minutes, followed by air cooling to room temperature. Subsequently, a medium-temperature aging treatment was performed at 960℃ for 4 hours, followed by air cooling to room temperature. A schematic diagram of the heat treatment process is shown below. Figure 1 The microstructure characteristics of the alloy after heat treatment and its creep life at 850℃ / 60MPa are shown in Table 1.

[0030] Example 2

[0031] Solid solution-strengthened high-temperature alloy pre-alloyed powder was prepared, with the following composition by weight percentage: Cr 19%-23%, Fe 18%-20%, Mo 8%-10%, Co 1%-2%, Si≤1%, Mn≤1%, C≤0.09%, S≤0.01%, P≤0.01%, O≤0.02%, and the remainder being Ni. Pre-alloyed powder with a particle size of 15-55 μm was prepared according to the above composition, and printed alloy blocks were obtained using a selective laser melting printer in a vacuum environment. The printed alloy blocks were subjected to high-temperature solid solution treatment at 1075℃ for 10 minutes, followed by air cooling to room temperature. Subsequently, a medium-temperature aging treatment was performed at 960℃ for 3 hours, followed by air cooling to room temperature. A schematic diagram of the heat treatment process is shown below. Figure 1 The microstructure characteristics of the alloy after heat treatment and its creep life at 850℃ / 60MPa are shown in Table 1.

[0032] Example 3

[0033] Solid solution strengthened high-temperature alloy pre-alloyed powder was prepared with the following composition by weight percentage: Cr 19%-23%, Fe 18%-20%, Mo 8%-10%, Co 1%-2%, Si≤1%, Mn≤1%, C≤0.09%, S≤0.01%, P≤0.01%, O≤0.02%, with the remainder being Ni. Pre-alloyed powder with a particle size of 15-55 μm was prepared according to the above composition, and printed alloy blocks were obtained using a selective laser melting printer in a vacuum environment. The printed alloy blocks were subjected to high-temperature solid solution treatment at 1100℃ for 30 minutes, followed by air cooling to room temperature. Subsequently, a medium-temperature aging treatment was performed at 960℃ for 4 hours, followed by air cooling to room temperature. A schematic diagram of the heat treatment process is shown below. Figure 1 The microstructure characteristics of the alloy after heat treatment and its creep life at 850℃ / 60MPa are shown in Table 1.

[0034] Comparative Example 1

[0035] Solid solution strengthened high-temperature alloy pre-alloyed powder was prepared with the following composition by weight percentage: Cr 19%-23%, Fe 18%-20%, Mo 8%-10%, Co 1%-2%, Si≤1%, Mn≤1%, C≤0.09%, S≤0.01%, P≤0.01%, O≤0.02%, with the remainder being Ni. Pre-alloyed powder with a particle size of 15-55 μm was prepared according to the above composition, and printed alloy blocks were obtained using a selective laser melting printer under vacuum. The printed alloy was subjected to creep testing directly at 850℃ / 60MPa without any heat treatment. The alloy microstructure characteristics and creep life at 850℃ / 60MPa are shown in Table 1.

[0036] Table 1 shows the microstructure characteristics and high-temperature creep properties of the heat-treated alloy and the printed alloy of this invention.

[0037]

[0038] Depend on Figure 2 and Figure 3 It is known that the average grain size of the additively manufactured solid solution-strengthened superalloy used in this invention after heat treatment is less than 40 micrometers. The alloy matrix consists of single-phase austenite, with spherical M6C-type carbides uniformly and discontinuously distributed at the grain boundaries. The alloy's creep life (850℃ / 60MPa) is higher than 90 hours. For additively manufactured solid solution-strengthened superalloys, in order to obtain a suitable high-temperature creep life, it is necessary to control the grain size and the morphology and distribution of the strengthening phase through appropriate heat treatment processes to achieve optimal microstructure matching and meet the structural and performance requirements for service. Therefore, the heat treatment method provided by this invention for improving the high-temperature creep performance of laser additively manufactured solid solution-strengthened superalloys has simple process steps and low cost. Its purpose is to control the microstructure of additively manufactured solid solution-strengthened superalloys to match their grain size and the morphology and distribution of precipitated phases, thereby improving the alloy's high-temperature creep performance.

[0039] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A heat treatment method for improving the high-temperature creep performance of laser additive manufacturing solid solution strengthened superalloys, characterized in that, Includes the following steps: 1) Selective laser melting printing: Pre-alloyed powder with a particle size of 15~55 μm is prepared from solid solution strengthened high-temperature alloy, and printed alloy blocks are obtained by selective laser melting printing in a vacuum environment; The solid solution strengthened high-temperature alloy is a solid solution strengthened high-temperature nickel-based alloy, comprising, by mass percentage: Cr 19%~23%, Fe 18%~20%, Mo 8%~10%, Co 1%~2%, Si≤1%, Mn≤1%, C≤0.09%, S≤0.01%, P≤0.01%, O≤0.02%, with the remainder being Ni; 2) High-temperature solution treatment: Heat the printed alloy block to 1075℃~1200℃, hold for 10~60 minutes, and air cool to room temperature; 3) Medium-temperature aging treatment: The alloy block after high-temperature solution treatment is heated to 940℃~980℃ and held for 2~4 hours, and then air-cooled to room temperature to complete the improvement of the high-temperature creep performance of the alloy. The average grain size of the solid solution strengthened high-temperature alloy after the final treatment is no more than 40 micrometers, and the internal structure is a single-phase austenite structure. At the grain boundaries, a uniform and discontinuously distributed spherical M6C phase is obtained. The average size of the M6C phase at the grain boundaries is no more than 4μm, the area fraction is no less than 0.3%, and it is uniformly spherically distributed at the grain boundaries.

2. The heat treatment method for improving the high-temperature creep performance of laser additive manufacturing solid solution strengthened high-temperature alloys according to claim 1, characterized in that, The solid solution strengthened high-temperature alloy after final treatment has a life of not less than 90 hours under creep conditions of 850℃ / 60MPa.

3. The heat treatment method for improving the high-temperature creep performance of laser additive manufacturing solid solution strengthened high-temperature alloys according to claim 2, characterized in that, The solid solution strengthened superalloy after final treatment has a creep life of 90~145 hours under 850℃ / 60MPa creep conditions.

4. The heat treatment method for improving the high-temperature creep performance of laser additive manufacturing solid solution strengthened high-temperature alloys according to claim 1, characterized in that, In step 1), a printed alloy block is prepared using a selective laser melting printer.

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