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CN-121972687-A - Heat treatment process for improving strength of nickel-based alloy FGH4098 manufactured by additive manufacturing

CN121972687ACN 121972687 ACN121972687 ACN 121972687ACN-121972687-A

Abstract

The invention discloses a heat treatment process for improving the strength of nickel-based alloy FGH4098 produced by additive manufacturing, and belongs to the technical field of metal additive manufacturing and heat treatment. The method comprises the steps of forming a FGH4098 alloy blank by adopting a laser selective melting technology (LPBF), carrying out high-vacuum packaging treatment on a cleaned sample to construct a clean independent microenvironment, and then carrying out direct aging heat treatment at the temperature of about 760 ℃. The invention eliminates the traditional high-temperature solid solution step, completely retains the special micron-sized fine crystal structure and high-density dislocation network in the printing state, simultaneously utilizes vacuum packaging to effectively isolate oxygen erosion in the heat treatment process, prevents oxidation depletion of key strengthening elements (Al and Ti) and ensures the full dispersion and precipitation of phases in a pure environment. The invention solves the problems of coarsening and softening of crystal grains and easy oxidative deformation in conventional aging caused by high-temperature solid solution in the prior art, obviously improves the tensile strength, hardness and dimensional stability of the alloy, and realizes the short-process precision manufacturing of high-performance components.

Inventors

  • LIU TENGYU
  • LI HEZONG
  • REN YONG
  • Qie Penglong
  • ZHAO LIGUO
  • HUANG SUXIA
  • CAO JINGJING

Assignees

  • 河北工程大学

Dates

Publication Date
20260505
Application Date
20260209

Claims (10)

  1. 1. A heat treatment process for improving the strength of nickel-base alloy FGH4098 for additive manufacturing, which is characterized by comprising the following steps: Step S1, providing nickel-based alloy FGH4098 prealloyed powder; S2, forming the prealloyed powder into an alloy blank by utilizing a laser selective melting technology (LPBF); s3, separating the alloy blank from the forming substrate and cleaning the surface of the alloy blank to obtain a sample to be treated; s4, vacuum packaging is carried out on the sample to be processed; S5, performing direct aging heat treatment on the sample, namely heating the sample to an aging temperature in a vacuum environment, preserving heat, and then cooling to room temperature; Wherein, the step S5 is directly performed without high-temperature solution treatment after the step S4 is completed.
  2. 2. The heat treatment process for improving the strength of an additive manufactured nickel-base alloy FGH4098 according to claim 1, wherein in the step S1, the chemical composition of the nickel-base alloy FGH4098 prealloyed powder comprises ：Cr:12.5～13.5%,Co:18.0～21.0%,Mo:3.5～4.5%,W:3.5～4.5%,Ti:3.4～4.0%,Al:3.2～3.8%,Nb:0.5～1.0%,C:0.02～0.06%,B:0.01～0.03%,Zr:0.03～0.06%, mass percent of Ni as the rest.
  3. 3. The heat treatment process for improving the strength of the additive manufacturing nickel-base alloy FGH4098 according to claim 1, wherein in the step S1, the particle size distribution range of the prealloyed powder is 15-45 m, and the Hall flow rate is 14-16S/50 g.
  4. 4. The heat treatment process for improving the strength of an additive manufactured nickel-base alloy FGH4098 according to claim 1, wherein the specific process conditions of step S2 include: Preheating a substrate to 80-100 ℃ before molding; the molding process is carried out under the protection of high-purity argon atmosphere with the oxygen content lower than 100 ppm.
  5. 5. The heat treatment process for improving the strength of an additive manufactured nickel-base alloy FGH4098 according to claim 4, wherein the laser scanning parameters used in the step S2 are: The laser power P is 188W; the scanning speed v is 1700mm/s, and the powder spreading layer thickness t is 30m; The scanning interval h is 30m; the scanning strategy employs a stripe scan pattern with an inter-layer rotation 90.
  6. 6. The heat treatment process for improving the strength of an additive manufactured nickel-base alloy FGH4098 according to claim 1, wherein the step S3 specifically comprises: after the substrate is cooled to room temperature, separating the alloy blank by adopting a linear cutting process; and ultrasonically cleaning the separated sample for 10-15 minutes by using acetone and absolute ethyl alcohol, and then drying.
  7. 7. The heat treatment process for improving the strength of an additive manufactured nickel-base alloy FGH4098 according to claim 1, wherein in the step S4, the vacuum packaging is specifically performed by placing a sample to be processed in a quartz glass tube, vacuumizing to a pressure lower than 510 -3 Pa, and sealing.
  8. 8. The heat treatment process for improving the strength of the additive manufactured nickel-base alloy FGH4098 according to claim 1, wherein in the step S5, the heating rate in the heating process is controlled to be 5-10 ℃ per minute.
  9. 9. The heat treatment process for improving the strength of an additive manufactured nickel base alloy FGH4098 according to claim 1, wherein in the step S5, the aging temperature is 7605 ℃ and the holding time is 80.5 hours.
  10. 10. The heat treatment process for improving the strength of an additive manufactured nickel base alloy FGH4098 according to claim 9, wherein the cooling manner in the step S5 is as follows: and discharging the heat from the furnace for air cooling after heat preservation is finished.

Description

Heat treatment process for improving strength of nickel-based alloy FGH4098 manufactured by additive manufacturing Technical Field The invention relates to the technical field of metal additive manufacturing and heat treatment, in particular to a heat treatment process for improving the strength of nickel-based alloy FGH4098 manufactured by additive manufacturing. Background As an advanced powder metallurgy nickel-based superalloy, the FGH4098 alloy is widely applied to manufacturing of hot end core components such as aerospace engine turbine discs and the like due to excellent high-temperature strength, creep resistance and good oxidation resistance and corrosion resistance. With the continuous development of manufacturing technology, the laser selective melting (LPBF) additive manufacturing technology is an important means for preparing FGH4098 complex structural components due to extremely high design freedom and near net shaping capability. The LPBF process is based on a layer-by-layer fusing process with extremely high cooling speed, so that the formed alloy naturally has micron-sized ultrafine grains and a high-density dislocation network structure, and the unique non-equilibrium microstructure has huge toughening potential. However, the current heat treatment regime for additive manufacturing FGH4098 alloys mostly follows the standard solid solution + aging heat treatment regime of conventional powder metallurgy or wrought alloys. Such conventional processes typically involve high temperature solid solution steps above 1090 ℃ with the core objective of eliminating the processing stresses and homogenizing the structure by sufficient diffusion of atoms. However, for additive manufacturing alloy, the high temperature treatment is a double-edged sword, the high temperature solid solution can lead to the recrystallization and remarkable growth of the special metastable fine crystal structure of LPBF while eliminating the stress, and the dislocation strengthening structure with high density can be restored to be annihilated in a large amount, so that the material not only loses the original excellent fine crystal strengthening and dislocation strengthening advantages, but also tends to be greatly reduced in strength due to the rapid coarsening of crystal grains. In order to avoid the problem of coarsening of the structure caused by high-temperature solid solution, some researches are attempted to adopt a direct aging process, namely omitting the solid solution step to directly carry out heat treatment. However, the existing direct aging process faces serious environmental control difficulties in the implementation process. Because the FGH4098 alloy contains a high proportion of active strengthening elements such as aluminum (Al), titanium (Ti) and the like, the FGH4098 alloy is extremely sensitive to the oxygen content in a heat treatment atmosphere. In a conventional industrial vacuum heat treatment furnace, even if a certain vacuum degree is maintained, during the aging heat preservation process for several hours to ten hours, a trace amount of residual oxygen or leaked gas in a hearth is still sufficient to react with the surface of a high-temperature sample, so that oxide scales are formed on the surface and even an alloy element depletion layer appears. This disruption of surface integrity not only reduces the fatigue life of the component, but also prevents uniform precipitation of the strengthening phase (phase) at the surface layer. In addition, the lack of a direct heating means for effective physical isolation is susceptible to furnace air flow disturbances or non-uniform radiation, resulting in uncontrollable thermal deformations of the delicate complex components during the release of residual stresses. Therefore, how to develop a novel heat treatment process which can not only completely reserve a printing state fine grain structure, but also provide extremely pure thermal environment to ensure surface integrity and fully separate out a strengthening phase becomes a key technical bottleneck for fully exerting the performance potential of the additive manufacturing FGH4098 alloy. Disclosure of Invention The invention mainly solves the technical problems that the conventional high-temperature solution heat treatment is adopted to cause the disappearance of fine crystal and dislocation structures and the reduction of strength in the conventional additive manufacturing FGH4098 alloy, and the direct aging process is easy to cause deformation and cracking due to residual stress and insufficient precipitation of strengthening phases. In order to achieve the above purpose, the present invention adopts the following technical scheme: The invention provides a heat treatment process for improving the strength of nickel-base alloy FGH4098 produced by additive manufacturing, which comprises the following steps: Step S1, providing nickel-based alloy FGH4098 prealloyed powder; S2, forming the prealloyed powd