Method for inhibiting cracks of additive manufacturing high-temperature alloy
By adjusting the content of the trace element B in high-temperature alloys and optimizing the parameters of selective laser melting technology, the problem of cracking in additive manufacturing of high-temperature alloys was solved, achieving crack-free, high-density forming suitable for aerospace components.
Patent Information
- Application Number
- CN202511745551.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-26
- Publication Date
- 2026-02-24
AI Technical Summary
High-temperature alloys manufactured by additive manufacturing are prone to cracking during the printing process, which is difficult to completely avoid with existing technologies. Furthermore, the mismatch between composition and process leads to high sensitivity to cracking.
By adjusting the content of trace element B through phase diagram simulation and combining it with process optimization, high sphericity alloy powder was prepared. Low energy density laser selective melting technology was then used to optimize the composition and process parameters to suppress cracking.
It achieves crack-free, high-density forming during additive manufacturing, meeting the mechanical performance requirements of high-temperature components, and is applicable to aerospace and other fields.
Smart Images
Figure CN121551631A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of metal additive manufacturing technology, and specifically to a method for suppressing cracks in additive manufacturing high-temperature alloys. Background Technology
[0002] High-temperature alloys, with their excellent high-temperature strength and creep resistance, are core materials for hot-end components in aerospace and energy fields. The composition design of traditional casting and forging processes (such as controlling major elements like Cr and Ni, and strengthening grain boundaries with trace elements like B and C) has become a mature system, matching the "overall heating-slow cooling" hot working characteristics of casting and forging to meet component performance requirements. However, additive manufacturing technologies (such as SLM and DED) have fundamentally different characteristics in their layer-by-layer melting and rapid solidification processes compared to traditional methods. Their strong non-equilibrium solidification behavior, high temperature gradients, and repeated cyclic heating-cooling effects mean that directly using traditional high-temperature alloy compositions during printing easily generates large residual stresses and triggers cracks. This is the core bottleneck restricting the industrialization of high-temperature alloy additive manufacturing.
[0003] Cracks in additive manufacturing high-temperature alloys are mainly classified into two categories: hot cracks, including solidification cracks and liquefaction cracks; and solid-state cracks, including strain-aging cracks and high-temperature thermoplastic cracks. The formation of these hot cracks is closely related to the solidification temperature range of the high-temperature alloy during additive manufacturing. The width of this range directly determines the duration and extent of the solid-liquid two-phase region during solidification. In traditional casting and forging processes, the solidification temperature range of the alloy is controlled within a narrow range through compositional design, and the slow cooling rate allows the solid-liquid two-phase region to smoothly pass through the solidification shrinkage stage. However, under the rapid cooling and solidification conditions of additive manufacturing, the segregation of trace elements in the high-temperature alloy easily forms a low-melting-point liquid phase film, significantly reducing the solidification termination temperature and broadening the solidification temperature range, thus making it easier to induce cracks. The root cause lies in the mismatch between the traditional high-temperature alloy composition and the additive manufacturing process. Existing solutions focus on optimizing process parameters (such as adjusting laser power and scanning speed) and post-heat treatment (such as HIP). The former can only reduce cracks but cannot completely prevent crack formation; the latter can only heal microcracks of a certain size and is costly.
[0004] Therefore, it is urgent to start from the essence of the composition, optimize the content of trace elements, and solve the cracking problem of additive manufacturing high-temperature alloys from the source. Summary of the Invention
[0005] Purpose of the invention: To address the technical pain points of difficult-to-eliminate cracks and poor composition-process compatibility in additive manufacturing of high-temperature alloys, this invention proposes a collaborative innovation method based on phase diagram simulation for composition design and process optimization, aiming to solve the problem of cracks in additive manufacturing of high-temperature alloys.
[0006] Technical solution: A method for suppressing cracks in additive manufacturing high-temperature alloys, comprising the following steps:
[0007] Step 1: Using phase diagram simulation analysis software, the mass fraction of element B is adjusted on the traditional high-temperature alloy basic composition to simulate the change of solidification temperature range under different B contents, and a new composition result with a narrower solidification temperature range is obtained.
[0008] Step 2: Based on the results obtained in Step 1, design the required mass percentage, prepare the ingredients, melt the master alloy using a vacuum induction melting furnace, and then obtain the master alloy bar after surface processing.
[0009] Step 3: The obtained high-temperature alloy rods with new composition are used to prepare powder using gas atomization (VIGA) or plasma rotating electrode technology (PREP);
[0010] Step 4: High-temperature alloy materials are printed using selective laser melting technology to obtain metallographic samples. The powder particle size range during selective laser melting is 15-53 μm.
[0011] Specifically, in step 1, the high-temperature alloys are GH5188 high-temperature alloy and IN738LC high-temperature alloy.
[0012] More specifically, the GH5188 high-temperature alloy has the following basic composition: Cr: 20-24 wt.%, Ni: 20-24 wt.%, W: 13-16 wt.%, B: ≤0.015 wt.%, C: 0.05-0.15 wt.%. The IN738LC high-temperature alloy has the following basic composition: Cr: 15.7-16.3 wt.%, Co: 8-9 wt.%, W: 2.4-2.8 wt.%, Al: 3.2-3.7 wt.%, Ti: 3-3.5 wt.%, B: 0.005-0.015 wt.%, Zr: 0.05-0.15 wt.%, C: 0.1-0.2 wt.%.
[0013] Specifically, in step 1, the alloy composition is designed by reducing the boron (B) content within the standard range to lower the solidification temperature range. The presence of B significantly expands the alloy's solidification temperature range. During the rapid solidification of SLM (Self-Melting Metal), when the liquid film between dendrites or grain boundaries has not yet fully solidified, adjacent grains have already contracted and generated tensile stress, which can lead to solidification cracks (also known as hot cracks). By reducing the B content, the number and continuity of these low-melting-point phases can be effectively reduced, narrowing the solidification temperature range and allowing the alloy to complete the liquid-solid transformation within a narrower temperature range, thereby significantly reducing the susceptibility to solidification cracks.
[0014] Specifically, in step 2, the mass fraction of element B in the newly designed high-temperature alloy is reduced to ≤0.005wt.%, and the solidification temperature range is ≤126℃.
[0015] Specifically, in step 3, when using gas atomization to produce powder, the pouring temperature is 1500-1550℃ and the atomization pressure is 0.5-0.6MPa.
[0016] Specifically, in step 3, when using plasma rotating electrode technology to make powder, the rotation speed is 20,000-30,000 r / min and the current is 1,200-1,500 A.
[0017] For this invention, PREP (Prep-Extraction Process) is preferentially used to obtain alloy powder with better sphericity and lower oxygen and nitrogen content. PREP technology uses centrifugal force to eject molten metal droplets from the end of a rotating electrode. The droplets spherize and cool in the air under surface tension. This process is carried out in a closed, inert atmosphere, eliminating crucible contamination. Therefore, the prepared powder has extremely high sphericity, few satellite particles, and lower oxygen and nitrogen content. High sphericity ensures good powder flowability and uniformity of powder distribution, which is a prerequisite for obtaining highly dense, defect-free printed parts. Lower oxygen and nitrogen content avoids the formation of brittle inclusions such as oxides and nitrides during printing, which can become the starting point for crack initiation.
[0018] Preferably, before step 4, the powder is vacuum dried at 120°C for 4-6 hours to remove adsorbed moisture; the forming chamber is filled with high-purity Ar (oxygen content ≤50ppm) to prevent oxidation. Removing moisture and strictly controlling the oxygen content can effectively prevent the formation of pores and oxidation during the printing process, avoiding these defects from becoming sources of cracks.
[0019] Specifically, in step 4, during selective laser melting, the forming parameters are: laser power 200-260W, scanning speed 800-1200mm / s, scanning spacing 0.08-0.12mm, and powder layer thickness 0.05mm. This invention employs a combination of "low laser power and high scanning speed" to achieve a low volumetric energy density process strategy. This process can: reduce the size of the molten pool and the heat-affected zone, reduce residual stress, and suppress element burn-off and harmful phase precipitation. Excessive energy can cause low-melting-point elements (such as B, which is strictly controlled in this scheme) to evaporate and burn off, disrupting the composition design, and may also promote grain coarsening and the formation of brittle phases. Low energy input helps maintain compositional stability and form fine microstructures.
[0020] Preferably, for this invention, the printing forming parameters are selected as a low energy density combination of low laser power and high scanning speed to reduce residual thermal stress. Based on the principle of low energy density and considering the need to ensure good fusion, the scanning speed is preferably 1000-1200 mm / s. This range can be well matched with a laser power of 200-250W and a scanning spacing of 0.08-0.10mm, and the calculated volumetric energy density is at a low level (about 40-65 J / mm³), which can achieve complete melting of powder and control heat input to the maximum extent. More preferably, for GH5188 alloy, the optimal forming parameters are: laser power 240W, scanning speed 1150mm / s, scanning spacing 0.08mm, and powder layer thickness 0.05mm; for IN738LC alloy, the optimal forming parameters are: laser power 200W, scanning speed 1050mm / s, scanning spacing 0.10mm, and powder layer thickness 0.05mm.
[0021] Beneficial Effects: This invention addresses the challenge of suppressing cracks in existing additive manufacturing high-temperature alloys. It employs a combination of compositional design optimization and process parameter optimization to achieve both the elimination of porosity defects and crack suppression, resolving the mismatch between traditional high-temperature alloy compositions and additive manufacturing processes. It has broad prospects for industrial application, applicable to various high-temperature alloys such as GH5188 and IN738LC, and can be extended to mainstream additive manufacturing processes such as selective laser melting and directional energy deposition.
[0022] This invention is particularly applicable to the forming of high-temperature alloys for high-temperature load-bearing components such as aerospace engine combustion chambers and turbine blades using processes such as selective laser melting (SLM) and directional energy deposition (DED). Through composition-process synergistic optimization, it achieves crack-free, high-density forming, meeting the mechanical performance and reliability requirements of high-temperature components. Attached Figure Description
[0023] Figure 1 The simulated phase diagrams for liquid phases with different amounts of element B are shown, where a: B content is 0.002 wt.%;
[0024] b: B content is 0.005 wt.%; c: B content is 0.009 wt.%;
[0025] Figure 2 Morphology of GH5188 powder with a thickness of 15-53 μm prepared by PREP technology;
[0026] Figure 3 The metallographic morphology of GH5188 with low element B content printed at low energy density;
[0027] Figure 4 The metallographic morphology of GH5188 with high B content printed at low energy density;
[0028] Figure 5 The metallographic morphology of GH5188 with low B content is printed at high energy density. Detailed Implementation
[0029] The technical solution of this application will be described in detail below through embodiments, but the protection scope of this application is not limited to the embodiments described.
[0030] Example 1
[0031] This embodiment provides a method for suppressing cracks in additive manufacturing of GH5188 cobalt-based superalloys by optimizing the composition design and printing process parameters to reduce the boron content. The specific implementation steps are as follows:
[0032] (1) Based on the composition of GH5188 high-temperature alloy (Cr: 20-24wt.%, Ni: 20-24wt.%, W: 13-16wt.%, B: ≤0.015wt.%, C: 0.05-0.15wt.%), the range of B element was reduced by ≤0.005wt.% using Jmatpro phase diagram simulation analysis software, resulting in a new composition with a narrower solidification temperature range;
[0033] (2) The raw materials are batched according to the required mass percentage, and the master alloy is melted in a vacuum induction melting furnace. The homogenization temperature is 1550-1600℃, the casting temperature is 1500-1550℃, and the master alloy bar is obtained after surface finishing.
[0034] (3) The new GH5188 high-temperature alloy rod was subjected to PREP powdering at a rotation speed of 22000 r / min and a current of 1400 A. After sieving, the powder was obtained with a particle size of 15-53 μm for laser selective melting.
[0035] (4) GH5188 high-temperature alloy material was printed using laser selective melting technology to obtain a metallographic block of 12×12×12mm. The forming parameters were: laser power 240W, scanning speed 1150mm / s, scanning spacing 0.08mm, and powder layer thickness 0.05mm.
[0036] (5) After grinding and polishing the metallographic block, conduct metallographic observation to analyze the distribution of cracks and pores.
[0037] Figure 1The simulation results for liquid phase with B contents of 0.002 wt.%, 0.005 wt.%, and 0.009 wt.% are shown, with calculated solidification temperature ranges of 110℃, 126℃, and 148℃, respectively. The solidification temperature range of the GH5188 high-temperature alloy gradually increases with increasing B content. A larger solidification temperature range increases the risk of liquid phase film tearing during molten pool solidification; therefore, the B content was designed to be reduced to 0.002 wt.%. After vacuum melting and PREP technology, the following results were obtained: Figure 2 The GH5188 powder with a diameter of 15-53μm shown has sphericity and satellite powder properties that meet printing requirements.
[0038] Figure 3 The metallographic morphology of GH5188 formed under low energy density conditions of 240W laser power and 1150mm / s scanning speed is shown. As can be seen from the figure, no microcracks or obvious pore defects are present in the entire field of view, indicating that defect-free dense forming of GH5188 was achieved under these process parameters.
[0039] Example 2
[0040] This embodiment provides a method for suppressing cracking in additive manufacturing of high-aluminum-titanium content IN738LC nickel-based superalloys by optimizing the composition design with reduced boron content. The specific implementation steps are as follows:
[0041] (1) Based on the composition of IN738LC nickel-based superalloy (Cr: 15.7-16.3wt.%, Co: 8-9wt.%, W: 2.4-2.8wt.%, Al: 3.2-3.7wt.%, Ti: 3-3.5wt.%, B: 0.005-0.015wt.%, Zr: 0.05-0.15wt.%, C: 0.1-0.2wt.%), the B element content was reduced to ≤0.005wt.% and the Zr element content was simultaneously controlled to 0.03-0.08wt.%, resulting in a new composition with a narrower solidification temperature range.
[0042] (2) The raw materials are batched according to the required mass percentage, and the master alloy is melted in a vacuum induction melting furnace. The homogenization temperature is 1500-1600℃, the casting temperature is 1550-1600℃, and the master alloy bar is obtained after surface finishing.
[0043] (3) The new IN738LC high-temperature alloy rods were subjected to PREP powdering at a rotation speed of 20000 r / min and a current of 1500 A. The powder was then sieved to obtain powder with a particle size of 15-53 μm for laser selective melting.
[0044] (4) IN738LC high-temperature alloy material was printed using laser selective melting technology to obtain a metallographic block of 12×12×12mm. The forming parameters were: laser power 200W, scanning speed 1050mm / s, scanning spacing 0.1mm, and powder layer thickness 0.05mm. Finally, IN738LC formed parts with fewer microcracks were obtained.
[0045] IN738LC alloy, as a typical precipitation-strengthened nickel-based superalloy, tends to accumulate Al and Ti between dendrites and grain boundaries during the final stage of solidification. These elements, in synergy with Bo, form a low-melting-point γ-γ' eutectic phase. This eutectic phase readily liquefies, forming a continuous liquid film. When the residual tensile stress exceeds the critical cracking stress of the liquid film, liquefaction cracks distributed along the grain boundaries will form. Reducing the Bo content suppresses segregation at grain boundaries, hindering the formation of liquid films at these locations and thus reducing the risk of liquefaction crack formation.
[0046] Comparative Example 1
[0047] Compared to Example 1, only the B element content was increased to 0.009 wt.%, while all other steps (vacuum melting, powdering, SLM process) were exactly the same, resulting in the following... Figure 4 The metallographic morphology results are shown. Compared with GH5188 powder with a low B content of 0.002 wt.%, GH5188 powder with a high B content exhibits a large number of intergranular cracks on its metallographic surface. Combined with simulation analysis results, the increase in B content increases the solidification temperature range of the alloy from 110℃ to 148℃, resulting in an expansion of the solid-liquid two-phase region of the molten pool, which makes it more prone to solidification cracking.
[0048] Comparative Example 2
[0049] Compared with Example 1, only the SLM process parameters were adjusted to high energy density: laser power 360W, scanning speed 1000mm / s, energy density E=360 / (1000×0.08×0.05)=90J / mm³, and the other steps were exactly the same. Figure 5 The metallographic morphology results shown indicate that, compared to the low energy density parameter selection in Example 1, microcracks still exist on the local surface of the sample under high energy density. However, compared to the forming results of GH5188 with high B content in Comparative Example 1, both the crack size and density are significantly reduced. Under high energy density, the molten pool morphology is deep and narrow with a steeper temperature gradient, making it easier to generate huge local tensile thermal stress and form solidification cracks.
[0050] Furthermore, due to excessive energy input, the molten pool mode changes from conduction mode to keyhole mode during material forming. The protective gas cannot escape during solidification and remains inside the molten pool, forming regular circular pores. This has an adverse effect on the densification forming of cobalt-based superalloys in additive manufacturing.
[0051] The above results indicate that after optimizing the composition of the GH5188 high-temperature alloy, crack-free dense forming of the material can be achieved by using optimized process parameters with low laser power, high scanning speed, and low energy density.
[0052] The above description is merely a preferred embodiment of this application and is not intended to limit this application.
Claims
1. A method for suppressing cracks in additive manufacturing high-temperature alloys, characterized in that, Includes the following steps: Step 1: Using phase diagram simulation analysis software, the mass fraction of element B is adjusted on the traditional high-temperature alloy basic composition to simulate the change of solidification temperature range under different B contents, and a new composition result with a narrower solidification temperature range is obtained. Step 2: Based on the results obtained in Step 1, design the required mass percentage, prepare the ingredients, melt the master alloy using a vacuum induction melting furnace, and then obtain the master alloy bar after surface processing. Step 3: Prepare powder from the obtained high-temperature alloy rod with new composition using gas atomization or plasma rotating electrode technology; Step 4: High-temperature alloy materials are printed using selective laser melting (SLM) technology. The forming parameters are: laser power 200-260W, scanning speed 800-1200mm / s, scanning spacing 0.08-0.12mm, and powder layer thickness 0.05±0.01mm to obtain metallographic samples. The powder particle size range during SLM is 15-53μm.
2. The method for suppressing cracks in additive manufacturing high-temperature alloys according to claim 1, characterized in that, In step 1, the high-temperature alloys are GH5188 high-temperature alloy and IN738LC high-temperature alloy.
3. The method for suppressing cracks in additive manufacturing high-temperature alloys according to claim 2, characterized in that, In step 1, the GH5188 high-temperature alloy has the following basic composition: Cr: 20-24 wt.%, Ni: 20-24 wt.%, W: 13-16 wt.%, B: ≤0.015 wt.%, C: 0.05-0.15 wt.%; the IN738LC high-temperature alloy has the following basic composition: Cr: 15.7-16.3 wt.%, Co: 8-9 wt.%, W: 2.4-2.8 wt.%, Al: 3.2-3.7 wt.%, Ti: 3-3.5 wt.%, B: 0.005-0.015 wt.%, Zr: 0.05-0.15 wt.%, C: 0.1-0.2 wt.%.
4. The method for suppressing cracks in additive manufacturing high-temperature alloys according to claim 1, characterized in that, In step 1, the content of element B is reduced within the standard composition range to lower the solidification temperature range during alloy composition design.
5. The method for suppressing cracks in additive manufacturing high-temperature alloys according to claim 1, characterized in that, In step 2, the mass fraction of element B in the newly designed high-temperature alloy is reduced to ≤0.005wt.%, and the solidification temperature range is ≤126℃.
6. The method for suppressing cracks in additive manufacturing high-temperature alloys according to claim 1, characterized in that, In step 3, when using air atomization to produce powder, the pouring temperature is 1500-1550℃ and the atomization pressure is 0.5-0.6MPa.
7. The method for suppressing cracks in additive manufacturing high-temperature alloys according to claim 1, characterized in that, In step 3, when using plasma rotating electrode technology to make powder, the rotation speed is 20,000-30,000 r / min and the current is 1200-1500 A.
8. The method for suppressing cracks in additive manufacturing high-temperature alloys according to claim 1, characterized in that, Before step 4, the powder is vacuum dried at 120°C for 4-6 hours to remove adsorbed moisture; the forming chamber is filled with high-purity Ar to prevent oxidation.
9. The method for suppressing cracks in additive manufacturing high-temperature alloys according to claim 1, characterized in that, In step 4, the forming parameters are: laser power 200-250W, scanning speed 1000-1200 mm / s, and scanning spacing 0.08-0.10mm.
10. The method for suppressing cracks in additive manufacturing high-temperature alloys according to claim 9, characterized in that, In step 4, the forming parameters are: laser power 240W, scanning speed 1150 mm / s, scanning spacing 0.08mm, and powder layer thickness 0.05mm; or: laser power 200W, scanning speed 1050mm / s, scanning spacing 0.10mm, and powder layer thickness 0.05mm.