A method of regulating laves phase in additive manufactured nickel-based superalloys
By controlling the heat input and mechanical energy during the additive deposition process through interlayer deformation composite additive manufacturing, the problem of the consumption of strengthening elements by the Laves phase in additive manufacturing was solved. The fragmentation and re-dissolution of the Laves phase were realized, which promoted the precipitation of the γ” phase and improved the mechanical properties of the formed parts.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHENYANG AEROSPACE UNIVERSITY
- Filing Date
- 2024-07-30
- Publication Date
- 2026-06-02
AI Technical Summary
In the additive manufacturing process, the formation of the Laves phase consumes the reinforcing elements in the matrix, reduces the strength of the matrix, and inhibits the precipitation of the reinforcing phase γ”. At the same time, the chain-like Laves phase is prone to causing the formed part to break, and traditional methods are difficult to effectively reduce its content and size.
By combining interlayer deformation composite additive manufacturing with interlayer plastic deformation and controlled heat input, the mechanical energy and heat input during the additive deposition process are regulated to promote the fragmentation and re-dissolution of the Laves phase into the matrix, while promoting the precipitation of the γ” phase. Plastic deformation is carried out by methods such as interlayer hammering, interlayer rolling and interlayer ultrasonic shot peening to control the grain recrystallization process.
It effectively reduced the content and size of the Laves phase, increased the content of strengthening elements in the matrix, promoted the precipitation of the γ” phase, and improved the mechanical properties of the molded parts.
Smart Images
Figure CN118957333B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of additive manufacturing technology for composite metal materials, and in particular to a method for controlling the Laves phase in additive manufacturing of nickel-based superalloys. Background Technology
[0002] Additive manufacturing, also known as 3D printing, is a technology that directly shapes three-dimensional solid parts by layering digital data from a 3D model and then processing it layer by layer. Laser-directed energy deposition (LDED) is one method of additive manufacturing, which involves feeding metal powder into a molten pool saturated by a laser to process parts. The metal powder melts and solidifies rapidly under the action of a high-energy laser, resulting in a dense and uniform microstructure and well-formed parts with good mechanical properties. Due to the large heat input of the laser, it can easily process materials with high melting points and difficult processing. However, severe elemental segregation occurs during the solidification process of laser deposition. Strengthening elements Nb and Mo exhibit high solid solubility in the liquid phase, leading to a large accumulation of Nb and Mo atoms in the residual liquid phase, ultimately resulting in the formation of long-chain Laves phases between dendrites. The formation of the Laves phase consumes strengthening elements in the matrix, thereby reducing the matrix strength and inhibiting the precipitation of the strengthening phase γ”. Simultaneously, the chain-like Laves phase easily serves as a crack propagation path, making the formed part prone to fracture. Therefore, reducing the Laves phase content and its size are effective ways to improve material properties. Traditionally, controlling the cooling rate and temperature gradient during additive manufacturing is used to influence Laves phase formation. Reference 1 (CN202110864041) reduces elemental segregation and thus lowers the volume fraction of the Laves phase by increasing the solidification rate of the molten pool during laser deposition; however, its effect on the Laves phase content is not significant and it does not promote the formation of the strengthening phase γ”. Reference 2 (CN 114799204 A) reduces the Laves phase content in additively manufactured high-temperature alloys by mixing nano-carbon powder with high-temperature alloy powder; however, the addition of carbon generates a large number of continuously distributed carbides, which adversely affects the material's plasticity. Summary of the Invention
[0003] To address the shortcomings of existing technologies, this invention provides a method for controlling the Laves phase in additive manufacturing of nickel-based superalloys; the method of reducing the Laves phase content and strengthening the precipitated phase through interlayer deformation composite additive manufacturing can improve the mechanical properties of the formed parts.
[0004] A method for controlling the Laves phase in additive manufacturing of nickel-based superalloys includes the following steps:
[0005] Step 1: Polish the substrate to remove the oxide film and clean it with an alkaline solution. Dry the metal powder and put it into the powder feeder.
[0006] Step 2: Create a 3D model of the specimen to be printed, slice the model into layers and plan the trajectory, and import the generated trajectory planning program into the additive manufacturing system;
[0007] Step 3: Perform single-layer additive deposition;
[0008] Step 4: Perform interlayer plastic deformation treatment on the surface of the deposited layer to achieve the required deformation amount;
[0009] Step 5: After the deposited layer, which has undergone interlayer plastic deformation treatment, is cooled to room temperature, additive deposition is continued on its surface;
[0010] Step 6: Alternate additive deposition and interlayer plastic deformation to finally obtain a shaped part with reduced Laves phase content.
[0011] The method for controlling the Laves phase in additive manufacturing of nickel-based superalloys, wherein the influence depth H of the interlayer plastic deformation in step 4 is described above. D Must meet
[0012] H D >H R +H A
[0013] In the formula H D H represents the depth of influence of interlayer plastic deformation, i.e., the depth of work hardening caused by a single-layer plastic deformation process. R H is the remelting depth, which is the depth to which the previous layer remelts when a new layer is deposited. A The average layer thickness after plastic deformation;
[0014] In the method for controlling the Laves phase in additive manufacturing of nickel-based superalloys, step 5 involves a distance H from the bottom of the molten pool. A At a temperature T, when T≤T R When T < T, all grains recrystallize, reducing the Laves phase content throughout the sample microstructure; when T < T R Grain recrystallization occurs in the grains, and the content of the Laves phase in the local structure of the sample decreases; among which, T R The critical recrystallization temperature is T, where T is the distance from the bottom of the molten pool by H. A The temperature at that location in, Where α is the net input power, α is the thermal diffusivity, and T is the net input power. s Let T0 be the velocity of the heat source, and C be the room temperature. p Let K0 be the specific heat capacity, t be the wall thickness, and K0() be the zeroth-order Bessel function of the first kind;
[0015] The method for controlling the Laves phase in additive manufacturing of nickel-based superalloys, wherein in step 5 of the additive deposition process, the heat input is controlled by adjusting the input power and the moving speed of the heat source during the additive deposition process, thereby controlling the proportion of grain recrystallization and the content of the Laves phase in the additive manufacturing sample;
[0016] The method for controlling the Laves phase in additive manufacturing of nickel-based superalloys includes interlayer plastic deformation processes such as interlayer hammering, interlayer rolling, and interlayer ultrasonic shot peening. The equipment for generating interlayer plastic deformation includes pneumatic hammers, hydraulic presses, and electromagnetic hammers.
[0017] The method for controlling the additive manufacturing of the Laves phase in nickel-based superalloys, wherein the heat source for additive deposition includes laser, electric arc, electron beam and ion beam.
[0018] The beneficial effects of adopting the above technical solution are as follows:
[0019] This invention provides a method for controlling the Laves phase in additive manufacturing of nickel-based superalloys. By introducing a large amount of mechanical energy during laser deposition through interlayer deformation, the Laves phase is fragmented, generating numerous dislocations within the material. The fragmented Laves phase is smaller in size, making it easier to dissolve. Simultaneously, the generation of dislocations provides more diffusion channels for Nb atoms, facilitating their diffusion. During subsequent layer deposition with heat input, recrystallization occurs around subgrains formed by dislocation entanglement. This recrystallization process, accompanied by grain boundary migration, further promotes the dissolution of the Laves phase back into the matrix. The substantial dissolution of the Laves phase into the matrix increases the content of the strengthening element Nb within the matrix. Simultaneously, the interlayer deformation introduces numerous dislocations, and the aggregation of Nb near these dislocations promotes the in-situ precipitation of the γ” phase under the cyclic heat input during subsequent layer additive manufacturing. Interlayer deformation reduces both the content and size of the Laves phase, while simultaneously promoting the formation of the strengthening γ” phase, thereby improving mechanical properties. Attached Figure Description
[0020] Figure 1 This is a schematic diagram of an interlayer deformation composite additive manufacturing apparatus in an embodiment of the present invention.
[0021] Figure 2 This is a schematic diagram illustrating the evolution principle of precipitated phases during interlayer deformation composite additive manufacturing in an embodiment of the present invention.
[0022] Figure 3 The microstructure and precipitate content of the interlayer deformation composite additive manufacturing specimens in the embodiments of the present invention are shown. Detailed Implementation
[0023] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.
[0024] The specific implementation steps are as follows:
[0025] (1) Figure 1 This is a schematic diagram of an interlayer deformation composite additive manufacturing apparatus. In this embodiment, interlayer hammering composite laser-directed energy deposition is used for the composite manufacturing of GH4169. The optimal laser process parameters are determined to be: laser power P = 1800 W, laser movement speed 0.01 m / s, powder feed rate 15 g / min, and argon as the protective gas. After drying, the GH4169 powder is fed into the powder feeder for laser deposition additive manufacturing.
[0026] (2) After single-layer deposition using a laser, the specimen was allowed to cool to room temperature. Then, an air hammer was used to apply interlayer plastic deformation to the deposited portion. The air hammer head, controlled by a robot, moved along a set trajectory, applying pulses to the top of the deposited layer. The distance between the hammer head and the specimen surface was 10 mm, and the hammer head's moving speed was 2 mm / s, with two hammer blows performed. The hardness (H) of the specimen was measured and observed using a hardness meter and optical microscope. D =2.9mm, H R =2.3mm.
[0027] (3) Laser deposition was performed on the hammered surface, and the hammering and laser deposition were alternated in subsequent processes to finally complete the manufacturing of the specimen. The specimen thickness t = 5 mm and the average layer thickness H A =0.4mm, satisfying H D >H R +H A The parameter values described in Summary 4 of the Invention are as follows: C p =657.2(J / (Kg·℃)), t=5mm, H A =0.4mm, T s =0.01m / s, α=1.1(㎡ / s), T0=25℃, T R =910℃, therefore T = 697.7℃. <T R Recrystallization occurs in some grains. The evolution principle of precipitated phases during interlayer deformation composite additive manufacturing is illustrated in the diagram. Figure 2 As shown.
[0028] (4) The interlaminar hammer test specimens obtained in this example were subjected to microstructure analysis, such as... Figure 3The sample shown has alternating non-recrystallization and recrystallization regions, with Laves phase contents of 0.47% and 0.26% in the non-recrystallization and recrystallization regions, respectively. The Laves phase content in the sample obtained by deposition alone is 1.15%, indicating that the interlayer hammering process significantly reduces the Laves phase content. The above description is merely a preferred embodiment of this disclosure and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in the embodiments of this disclosure is not limited to the specific combination of the above-described technical features, but should also cover other technical solutions formed by any combination of the above-described technical features or their equivalents without departing from the above-described inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in the embodiments of this disclosure.
Claims
1. A method for controlling the Laves phase in additive manufacturing of nickel-based superalloys, characterized in that, Includes the following steps: Step 1: Polish the substrate to remove the oxide film and clean it with an alkaline solution. Dry the metal powder and put it into the powder feeder. Step 2: Create a 3D model of the specimen to be printed, slice the model into layers and plan the trajectory, and import the generated trajectory planning program into the additive manufacturing system; Step 3: Perform single-layer additive deposition; Step 4: Perform interlayer plastic deformation treatment on the surface of the deposited layer to achieve the required deformation amount; Step 5: After the deposited layer, which has undergone interlayer plastic deformation treatment, is cooled to room temperature, additive deposition is continued on its surface; Step 6: Alternate additive deposition and interlayer plastic deformation to finally obtain a shaped part with reduced Laves phase content; The influence depth H of the interlaminar plastic deformation mentioned in step 4 D Must satisfy: H D H R +H A ; In the formula H D H represents the depth of influence of interlayer plastic deformation, i.e., the depth of work hardening caused by a single-layer plastic deformation process. R H is the remelting depth, which is the depth to which the previous layer remelts when a new layer is deposited. A The average layer thickness after plastic deformation; In step 5, the distance from the bottom of the molten pool is H. A At a temperature T, when T <T R Grain recrystallization occurs in the grains, and the content of the Laves phase in the local structure of the sample decreases; among which, T R The critical recrystallization temperature is T, where T is the distance from the bottom of the molten pool by H. A The temperature at that location ,in, Where α is the net input power, α is the thermal diffusivity, and T is the net input power. s Let T0 be the velocity of the heat source, and C be the room temperature. p Let K0 be the specific heat capacity, t be the wall thickness, and K0() be the zeroth-order Bessel function of the first kind; In the additive deposition process in step 5, the heat input is controlled by adjusting the input power and the heat source moving speed during the additive deposition process, thereby controlling the proportion of grain recrystallization and the content of Laves phase in the additive manufacturing sample. The interlayer plastic deformation process includes interlayer hammering, interlayer rolling, and interlayer ultrasonic shot peening, and the equipment for generating interlayer plastic deformation includes pneumatic hammers, hydraulic presses, and electromagnetic hammers. The heat sources for additive deposition include lasers, electric arcs, electron beams, and ion beams.