Patent Application
20170216919
1. Field of the Disclosure
The disclosure relates to a method for removing prior particle boundaries and hole defects of a powder metallurgy high-temperature alloy, and belongs to the powder metallurgy material field.
2. Description of Related Art
Defects, such as prior particle boundaries (PPB), internal holes, or thermal induction holes of a powder metallurgy high-temperature alloy are main defects of a powder high-temperature alloy, and are difficult to be removed once formed, and severely reduce mechanical properties of an alloy.
With respect to the defect of prior particle boundaries of the powder metallurgy high-temperature alloy, Chinese patent CN102409276A discloses a method for removing prior particle boundaries of a powder metallurgy high-temperature alloy, comprising: performing high-temperature solution treatment on a powder metallurgy high-temperature alloy after direct hot isostatic pressing at a high-temperature solution treatment temperature of 1180-1220° C., and performing heat preservation for 1.5-4 h, so as to effectively remove or weaken prior particle boundaries. Chinese patent CN102676881A discloses a nickel-based powder metallurgy high-temperature alloy capable of removing prior particle boundaries. The alloy comprises FGH4096 and FGH4097; Hf with a percentage by weight of 0.15-0.9% is additionally added during a smelting process of the two alloys. MC type carbides are formed in powder particles by adding the element, namely the Hf, to reduce precipitation on the prior particle boundaries, so that the prior particle boundaries in the nickel-based powder metallurgy high-temperature alloy is removed after standard heat treatment is performed on the nickel-based powder metallurgy high-temperature alloy after direct hot isostatic pressing, and notch sensitivity of the alloy is improved in the aspect of mechanical properties. Chinese patent CN103551573A discloses a high-temperature alloy powder hot isostatic pressing process capable of preventing phase precipitation of prior particle boundaries. A hot isostatic pressing temperature in a first step should be within the range between an incipient melting temperature of a low-melting-point phase in the powder particles and a solidus of completely homogenized alloy plus 15° C.; gas pressure should be greater than or equal to 90 MPa; and time is greater than or equal to 20 min and less than or equal to 1 h. Heating is stopped after the first step is finished; a powder capsule is cooled in a furnace to a temperature below the incipient melting temperature of the low-melting-point phase of the alloy powder to preserve heat; the heat preservation process is a second step; holding time in the second step is greater than or equal to 2 h, to ensure that the low-melting-point phase formed during cooling after the first step can be completely dissolved during the heat preservation process and the pressure is greater than or equal to 90 MPa; heating is stopped and the capsule is cooled in the furnace to room temperature after the second step is finished. The disclosure can prevent precipitation of precipitated phases of carbides, and the like along prior particle boundaries of powder, so as to obtain a compact alloy with microscopic structures as equiaxed crystals. Chinese patent CN103447341A discloses an equal-channel extrusion mold for forming a powder high-temperature alloy blank, and the mold is used for improving organizational characteristics of a powder high-temperature alloy blank. After a blank enters the mold, a round section of the blank is twisted to be elliptical and then to be round again, and the deformation is a combination of twisting and shearing deformation and extruding deformation, and thus a combination of multiple deformation modes in one-pass extruding process is implemented. At a transitional section of deformation and twisting, due to twisting deformation of an elliptical twisting surface, the blank rotates and is subjected to shearing strain under an action of shearing stress, so as to implement shearing and crushing of crystal grains and further achieve the effect of refining the grains. Simultaneously, since the blank is limited by a mold cavity, intracrystalline deformation of the blank in the state of pressure stress is difficult, and thus the development of various original microscopic defects in a deformed body can be inhibited. Since the refining effect of the grains in the disclosure is obvious, prior particle boundaries are removed thoroughly, and comprehensive mechanical properties of the powder high-temperature alloy blank are obviously improved.
The foregoing disclosures all remove prior boundaries of powder particles by treating green bodies after powder forming, which is a remedial measure adopted after the prior boundaries of powder particles are formed. Limited by processing factors, the effect of removing the prior boundaries of powder particles is limited, or industrial application cannot be implemented.
The foregoing patents for invention do not relate to how to remove hole effects of a powder metallurgy high-temperature alloy.
The hole defects in a powder high-temperature alloy comprise internal holes and thermal induction holes. The internal holes are mainly residual holes caused by powder hollow defects; and the thermal induction holes are hole defects caused by expansion generated by residual gases in a heat treatment process. Therefore, the powder hollow defects are main sources of the hole defects of the powder high-temperature alloy.
A hollow center of powder is a defect that commonly exists in atomized powder, and is determined by atomization process characteristics, and cannot be avoided. A hollow center formed inside atomized powder is completely sealed, and is difficult to be removed in a subsequent powder forming process, and resides inside a material to form a residual hole. Residual gases sealed in atomization hollow defects expand in a subsequent heat treatment process to form thermal induction holes, or induce cracks. The holes severely reduce mechanical properties of a powder high-temperature alloy, in particular, creep rupture life and fatigue properties.
Currently, in powder prepared by using an atomization process, a hollow ratio of large-particle-size powder is relatively high. For a long time, hollow powder is removed by means of powder screening in the art. A screening method can remove large-particle-size hollow powder, but cannot completely remove hollow powder, because hollow defects also occur to screened small-size powder. A control atomization process is generally used to control hollow defects that occur to atomized powder. However, characteristics of an atomization process determine that the control atomization process can only reduce a powder hollow ratio, but cannot completely remove powder hollow defects.
With respect to internal holes and thermal induction holes, caused by powder hollow defects, of a powder high-temperature alloy material, there has not been any public report home and abroad that internal holes and thermal induction holes are removed by removing hollow defects of atomized alloy powder.
So far, there has not been any public report home and abroad that hollow defects of atomized alloy powder are removed by means of ball milling treatment, to obtain surface activated solid powder, thereby removing prior boundaries, internal holes, and thermal induction holes of powder particles.
The disclosure is directed to provide a method for removing prior particle boundaries and hole defects of a powder metallurgy high-temperature alloy.
A method for removing prior particle boundaries and hole defects of a powder metallurgy high-temperature alloy of the disclosure includes first performing mechanical ball milling treatment on high-temperature alloy powder prepared by using an atomization method to prepare surface activated solid powder, then thermosetting the powder to form a shape, and preparing a powder metallurgy high-temperature alloy.
In a method for removing prior particle boundaries and hole defects of a powder metallurgy high-temperature alloy of the disclosure, granularity of the atomized alloy powder is less than or equal to 150 μm (−100 meshes), preferably less than or equal to 106 μm (−150 meshes), and further preferably less than or equal to 75 μm (−200 meshes).
In a method for removing prior particle boundaries and hole defects of a powder metallurgy high-temperature alloy of the disclosure, in ball milling, a used ball mill is one of a planetary ball mill, a stirring ball mill, and a roller drum ball mill, and preferably the planetary ball mill.
In a method for removing prior particle boundaries and hole defects of a powder metallurgy high-temperature alloy of the disclosure, ball milling is performed under protection of an inert gas.
In a method for removing prior particle boundaries and hole defects of a powder metallurgy high-temperature alloy of the disclosure, atomized powder is put into a ball mill pot with a ball-to-powder ratio of: (8-12): 1, and ball milling is performed in a planetary ball mill for 1-4 h at a ball milling rotation speed of 250-350 r/min.
In a method for removing prior particle boundaries and hole defects of a powder metallurgy high-temperature alloy of the disclosure, atomized powder is put into a ball mill pot with a ball-to-powder ratio of (8-15): 1, and ball milling is performed in a stirring ball mill for 2-6 h at a ball milling rotation speed of 60-150 r/min.
In a method for removing prior particle boundaries and hole defects of a powder metallurgy high-temperature alloy of the disclosure, thermosetting forming uses one forming manner of hot iso-hydrostatic forming, hot extrusion forming, and plasma sintering forming.
In a method for removing prior particle boundaries and hole defects of a powder metallurgy high-temperature alloy of the disclosure, the hot iso-hydrostatic forming is: 1000-1250° C./100-150 MPa/4 h hot iso-hydrostatic forming.
In a method for removing prior particle boundaries and hole defects of a powder metallurgy high-temperature alloy of the disclosure, the hot extrusion forming is: putting mixed powder obtained in step I into a steel capsule, vacuuming the steel capsule to equal to or less than 10−1 Pa, performing degasification for equal to or greater than 60 min, and performing sealing welding; and then performing hot extrusion forming at 900-1200° C. with an extrusion ratio of (6-15): 1.
In a method for removing prior particle boundaries and hole defects of a powder metallurgy high-temperature alloy of the disclosure, the plasma sintering forming is: 1000-1250° C./40-150 MPa/5-10 min plasma sintering forming.
In a method for removing prior particle boundaries and hole defects of a powder metallurgy high-temperature alloy of the disclosure, solution treatment and aging treatment are performed on a material of the high-temperature alloy formed by thermosetting; processing parameters of the solution treatment are: performing heat preservation for 1-2 h at 1000-1250° C., and performing air cooling; and processing parameters of the aging treatment are: performing heat preservation for 4-10 h at 700-900° C., and performing air cooling.
The present invention proposes to perform mechanical ball milling treatment on atomized powder to improve surface activity of the powder and remove internal hollow defects of powder particles, so as to remove prior boundaries, internal holes, and thermal induction holes of the powder particles, thereby improving comprehensive mechanical properties.
After ball milling treatment is performed on atomized powder, surfaces of the powder are activated, and powder with high surface activity is obtained, so that in thermosetting forming, prior boundaries of the powder can be effective removed to improve interface bonding strength. Powder deforms after ball milling, and internal hollow defects and condensation shrinkage cavities of powder particles are removed to obtain completely solid powder. A gas sealed in the solid powder is released, so as to effectively remove internal holes and thermal induction holes in thermosetting forming, thereby improving comprehensive mechanical properties. The atomized powder deforms after ball milling treatment, so as to facilitate recrystallization to form equiaxed crystal structures, thereby improving properties.
Based on the above, according to a method for removing prior particle boundaries and hole defects of a powder metallurgy high-temperature alloy, ball milling treatment is performed on atomized pre-alloyed powder to obtain solid powder with high surface activity, then thermosetting forming is performed to prepare a powder metallurgy high-temperature alloy. The disclosure has a simple process and high production efficiency, so as to facilitate large-scale preparation and application.
The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the disclosure and, together with the description, serve to explain the principles of the disclosure.
According to a metallographic observation result of
According to an SEM observation result of
According to an SEM observation result of
According to an observation result of an optical microscope of
Reference will now be made in detail to the present preferred embodiments of the disclosure, examples of which are illustrated in the accompanying drawings.
Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.
The disclosure is further described below with reference to specific embodiments.
Comparative example: direct plasma sintering is performed on atomized powder to prepare Rene 104 nickel-based high-temperature alloy.
Plasma sintering is performed on gas atomized Rene 104 nickel-based pre-alloyed powder (components are Ni-13Co-16Cr-4Mo-4W-2.2Al-3.7Ti-0.77Nb (wt %)); processing parameters are: 1150° C./40 MPa/heat preservation for 5 min, and then solution treatment is performed; the solution treatment is performed at 1180° C. for 1 h, and furnace cooling is performed; and then aging treatment s performed at 815° C. for 8 h to obtain a nickel-based high-temperature alloy.
Gas atomized Rene 104 nickel-based pre-alloyed powder is put into a ball mill pot with a ball-to-powder ratio of 10:1, and ball milling is performed in a planetary ball mill for 1.5 h at a ball milling rotation speed of 250 r/min under protection of argon, to obtain ball milling nickel-based high-temperature alloy powder.
Plasma sintering is performed on ball milling nickel-based high-temperature alloy powder at 1150° C./40 MPa, and heat preservation is performed for 5 min, then solution treatment is performed; the solution treatment is performed at 1180° C. for 1 h, and furnace cooling is performed; then, aging treatment is performed at 815° C. for 8 h to obtain a nickel-based high-temperature alloy.
Gas atomized Rene 104 nickel-based pre-alloyed powder is put into a ball mill pot, and ball milling is performed in a stirring ball mill for 3 h at a ball milling rotation speed of 100 r/min under protection of argon, to obtain ball milling nickel-based high-temperature alloy powder.
Ball milling powder is put into a steel capsule; vacuuming and sealing welding are performed on the steel capsule; hot extrusion forming is performed at 1100° C. with an extrusion ratio of 10:1 to obtain a highly compact nickel-based alloy bar; finally, solution treatment is performed at 1115° C. for 1 h and performed at 1170° C. for 3 h and air cooling is performed; aging treatment is performed at 845° C. for 4 h and performed at 760° C. for 8 h and air cooling is performed, to obtain a nickel-based high-temperature alloy.
It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present disclosure without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the present disclosure cover modifications and variations of this disclosure provided they fall within the scope of the following claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201510103503.6 | Mar 2015 | CN | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2016/075845 | 3/8/2016 | WO | 00 |
