JP2022553315A - FeCrAl printable powder material for additive manufacturing and additively manufactured objects and uses thereof - Google Patents

Abstract

The present disclosure relates to novel additively manufactured printable powder materials and additively manufactured objects and uses thereof. The present disclosure also relates to additive manufacturing methods for making objects. [Selection drawing] Fig. 1

Description

The present disclosure relates to novel additively manufactured printable powder materials and additively manufactured objects and uses thereof. The present disclosure also relates to additive manufacturing methods for making objects.

Additive manufacturing is an increasingly attractive solution for manufacturing functional prototypes and components made of metal, especially those with complex designs.

Ferritic alloys containing aluminum are attractive for use in electrical heating and high temperature applications. One problem with these alloys, however, is that they are difficult to weld due to their brittle nature. Additionally, these alloys can be difficult to machine. Therefore, manufacturing complex structures in these alloys can be difficult and complex. The present disclosure aims to solve or at least reduce the above problems.

Accordingly, one aspect of the present disclosure is to provide a printable ferritic iron-chromium-aluminum (FeCrAl) metal powder composition for use in additive manufacturing. Accordingly, the present disclosure is a printable ferritic FeCrAl powder composition, wherein the FeCrAl powder composition contains, in weight percent,
Cr 9.0-25.0,
Al 2.5-8.0,
Si≤3.0,
Mo ≤ 4.0,
Ni≤1.0,
Mn≤1.0,
C≦0.1,
O≤0.2,
S ≤ 0.01,
P≤0.01,
N≤0.1,
Ti≤1.7,
Y≤3.0,
Nb ≤ 3.3,
Zr ≤ 3.3,
V≤1.8
Ta + Hf ≤ 6.5
La ≤ 1.0,
Ce≤1.0,
A printable ferritic FeCrAl powder composition comprising the balance Fe and unavoidable impurities, wherein the FeCrAl powder composition has a powder particle size distribution between 4 and 200 μm, such as between 10 μm and 120 μm.

The powder has good flowability, good packing density and good spreadability and is therefore excellent for printing. A printable powder composition is also a gas-atomized ferritic iron-chromium-aluminum (FeCrAl) powder composition, meaning that the powder was obtained by a gas-atomization method. The printable ferritic FeCrAl powder composition is essentially fully dense, has excellent high temperature oxidation properties, and is advantageous for obtaining 3D shaped objects with excellent high temperature creep properties. Additionally, the powder may also be sieved to a particular desired particle size distribution.

The present disclosure also relates to additively manufactured objects made from said FeCrAl powder, including alloying elements within the scope of the FeCrAl powder defined above as: The 3D shape of the additively manufactured object depends on the end use. The inventors have surprisingly found an additively manufactured additive manufactured from an FeCrAl powder as defined above or below, thereby comprising an alloy consisting of the same elements within the same range of the powder as defined above or below. It has been found that the bodies have good mechanical properties at high temperatures, more specifically good creep resistance and even higher oxidation resistance at high temperatures.

Additively manufactured objects are particularly useful as electrical heating elements or components in high temperature applications (applications operating between 400-1350° C.) or as components in electrical heating applications. The object can also be used to protect another object from hot wear and corrosion. Therefore, the object can be used for both electrical heating and high temperature applications.

Another aspect of the present disclosure is to provide an additive manufacturing method. Accordingly, the present disclosure is an additive manufacturing method for manufacturing an object as defined above or below of a powder as defined above or below, wherein the additive manufacturing method comprises a powder bed fusion additive manufacturing method or a directional An additive manufacturing method selected from energy deposition (DED).

FIG. 1 shows the difference in creep properties at 900° C. and 1100° C. and 1200° C. between printed samples and conventionally produced alloys. FIG. 2 shows the difference in mass gain at 1100° C. between printed samples and conventionally produced alloys. 1 is a photomicrograph of an object produced from a powder as defined above or below using DED;

The present disclosure is a printable ferritic FeCrAl powder composition, wherein the FeCrAl powder composition comprises, in weight percent (wt%),
Cr 9.0-25.0,
Al 2.5-8.0,
Si≤3.0,
Mo ≤ 4.0,
Ni≤1.0,
Mn≤1.0,
C≦0.1,
S ≤ 0.01,
P≤0.01,
N≤0.1,
O≤0.2,
Ti≤1.7,
Y≤3.0,
Nb ≤ 3.3,
Zr ≤ 3.3,
V≤1.8
Ta + Hf ≤ 6.5
La < 1.0,
Ce<1.0,
The remainder consists of Fe and unavoidable impurities,
It relates to a printable ferritic FeCrAl powder composition, wherein the FeCrAl powder composition has a powder particle size distribution of 4-200 μm, such as 10-120 μm. Further, therefore, one aspect of the present disclosure is to provide a printable ferritic FeCrAl powder composition that can be used in additive manufacturing processes to obtain objects of complex structure and excellent mechanical properties. The term "printable" means that the powder can be used in at least one additive manufacturing method.

Most of the alloying elements of the powder are described below. The description lists some of the element's important properties. However, that list should not be considered an exhaustive list. Elements may have other properties not listed here.

Chromium (Cr)
Chromium promotes the formation of the Al ₂ O ₃ layer on the alloys defined above or below through the so-called tertiary element effect, ie by the formation of chromium oxide in a transient oxidation step. Chromium shall be present in the alloy defined above or below in an amount of at least 9 wt%. As the Cr content increases, the solid-solution hardening effect on the ferrite structure increases. From about 11 wt% Cr and above, the ferrite structure becomes unstable in the temperature range of 300-500°C. The ferrite can then be decomposed into one low-Cr ferrite phase and one high-Cr ferrite phase. When this happens, the material becomes harder and more brittle. Since this instability increases with increasing Cr, the maximum Cr is set at 25 wt%. Thus, according to one embodiment of the present disclosure, the Cr content is 18 to 24 wt%, such as 19 to 23.5 wt%. Thus, according to another embodiment of the present disclosure, the Cr content is between 9 and 11 wt%, and thus, according to yet another embodiment, the Cr content is between 9 and 15 wt%.

Aluminum (Al)
Aluminum is a key element in powders defined above or below because it forms a dense, thin oxide Al ₂ O ₃ when exposed to oxygen at elevated temperatures, protecting the underlying alloy surface from further oxidation. is. _The amount of aluminum is at _{least 2} to ensure that the _Al2O3 layer is formed and that there is enough aluminum to repair the _{Al2O3 layer} if it is damaged. should be 0.5 wt %. However, aluminum adversely affects the formability of objects obtained from the powder composition and the amount of aluminum should not exceed 8 wt% in the powder defined above or below. According to one embodiment, Al is 3-7 wt%. According to another embodiment, the Al is 3-6 wt%, such as 4-6 wt%, such as 3.5-6 wt%.

Silicon (Si)
In FeCrAl alloys, silicon is often present at levels up to about 0.5 wt%. Thus, according to one embodiment, Si is present at levels up to 0.5 wt%. However, Si may play an important role for improving oxidation and corrosion resistance. Thus, Si may be present from greater than 0.5 to 3 wt%, such as from 1 to 3 wt%, such as from 1 to 2.5 wt%, such as from 1.5 to 2.5 wt%. The upper limit of Si is due to increased susceptibility to formation of brittle Cr ₃ Si and σ phases during long-term exposure. Therefore, the addition of Si must be done in consideration of the content of Al and Cr.

manganese (Mn)
Manganese may be present as an impurity in the powders defined above or below. Manganese can also adversely affect oxidation lifetime above 1100°C. Therefore, the maximum content of Mn is up to 1.0 wt%. According to one embodiment, the content of Mn is ≦0.5 wt %.

Molybdenum (Mo)
Molybdenum may be an impurity or added as an alloying element. In embodiments where Mo is considered an impurity, its maximum level is 0.5 wt% or less. In embodiments where Mo is considered an alloying element and is added to provide a solid solution hardening effect, its minimum level is greater than 0.5 wt%, such as greater than 1.0 wt%, such as 1.0-4.0 wt% is.

carbon (C)
Carbon may be included to increase strength. At levels that are too high, carbon can make the material difficult to form and adversely affect corrosion resistance. Therefore, C is limited to ≤0.1 wt%, such as ≤0.05 wt%. According to one embodiment, the C content is 0.001 to 0.1 wt%.

Nitrogen (N)
Nitrogen may be included to increase strength. Nitrogen can also be present as an unavoidable impurity resulting from the manufacturing process. At levels that are too high, nitrogen can make the material difficult to form and adversely affect corrosion resistance. Therefore, N is limited to ≤0.1 wt%. According to one embodiment, the N content is 0.001 to 0.1 wt%.

oxygen (O)
Oxygen may be present as an impurity resulting from the manufacturing process. Therefore, O is limited to ≤0.2 wt%, such as ≤0.1 wt%.

Reactive element (RE)
As defined in this disclosure, reactive elements are highly reactive with carbon, nitrogen and oxygen. Yttrium (Y), titanium (Ti), zirconium (Zr), niobium (Nb), vanadium (V), hafnium (Hf), tantalum (Ta), lanthanum (La), Ce ( cerium), and these elements may be added.

According to the present disclosure, these elements have the following contents in the present powder, and therefore in objects made from the powder.
Ti ≤ 1.7 wt%,
Y ≤ 3.0 wt%,
Nb ≤ 3.3 wt%,
Zr ≤ 3.3 wt%,
V ≤ 1.8 wt%,
Ta + Hf ≤ 6.5 wt%,
La ≤ 1.0 wt%,
Ce≤1.0 wt%.

According to one embodiment, the FeCrAl powder defined above or below may have these elements in the following weight percentages (wt %).
Ti≦0.5,
Y≤1.0,
Nb ≤ 0.5,
Zr≤0.5,
V≤0.5,
Ta + Hf ≤ 1.0,
La≤0.5,
Ce≤0.5.

According to one embodiment, the printable FeCrAl powder composition contains, in weight percent,
Cr 18-24,
Al 4-6,
Mn≤0.5,
Si ≤ 0.5 or more than 0.5 to 3,
Mo ≤ 0.5,
Ti≦0.5,
Y≤1.0,
Nb ≤ 0.5,
Zr≤0.5,
V≤0.5,
Ta + Hf ≤ 1.0,
La≤0.5,
Ce≤0.5
The balance is Fe and unavoidable impurities, and C is ≤0.1 wt% or C is ≤0.05 wt%.

According to another embodiment, the printable FeCrAl powder composition comprises, in weight percent,
Cr 18-24,
Al 4-6,
Mn≤0.5,
Si ≤ 0.5 or more than 0.5 to 3,
Mo 1-4,
Ti≦0.5,
Y≤1.0,
Nb ≤ 0.5,
Zr≤0.5,
V≤0.5,
Ta + Hf ≤ 1.0,
La≤0.5,
Ce≤0.5
The balance is Fe and unavoidable impurities, and C is ≤0.1 wt% or C is ≤0.05 wt%.

Iron (Fe) and incidental impurities both constitute the balance of the powder or body as defined above or below.

Examples of incidental impurities include, but are not limited to, metals that form low melting point phases, as these low melting point phases have been shown to affect crack resistance properties.

It has therefore been found that by removing certain alloying elements in the FeCrAl powder, it is possible to achieve a product with, but not limited to, excellent high temperature corrosion resistance and creep strength. Examples of such elements are cobalt, copper, zinc and magnesium.

According to embodiments, the powder particle size distribution may be selected from 4-200 μm, 10-120 μm, 10-90 μm.

Additively manufactured objects manufactured using ferritic FeCrAl powders defined above or below perform well at operating temperatures up to 1350°C. Furthermore, the body has outstanding high temperature corrosion resistance and high resistance to oxidation, sulfidation and carbonization. Additionally, additively manufactured objects have significant high temperature creep strength and high dimensional stability and high electrical resistivity compared to conventionally manufactured objects.

The additive manufacturing methods described above or below use computer-aided design of printed 3D molded objects that are decomposed into 2D thin slices by using software that also links the generated data to hardware. .

According to one embodiment of the present disclosure, a powder bed fusion additive manufacturing method is used. According to another embodiment, the powder bed fusion manufacturing method is selected from Selective Laser Melting (SLM) or Electron Beam Melting (EBM). Both of these methods use a powder bed. The powder layer is exposed to an energy source and thereby melted or at least partially melted. New powder layers are applied until the desired object is obtained. In SLM, the energy source is one or more laser beams, such as an energy source continuous laser beam or a pulsed laser beam, and in EBM the energy source is an electron beam.

SLM is performed in an inert atmosphere such as an argon or nitrogen atmosphere. Additionally, the method may use supports when needed, for example to reinforce small angles, which are then removed. Furthermore, SLM printing is performed directly on the loose powder layer.

In EBM, each powder layer may be preheated before being locally melted by the electron beam. This method is performed in vacuum and at high temperature. Furthermore, in EBM, each new powder layer is first pre-sintered with an electron beam before the actual printing of the powder layer begins.

According to one embodiment, the thickness of the powder layer is between 10 and 250 μm. For example, for SLM the layer thickness can be between 10 and 80 μm and for EBM the layer thickness can be between 10 μm and 250 μm.

According to a further embodiment, the power of the energy source during printing is 80-400 W if a laser beam is used and 300-1000 W if an electron beam is used. Optionally, multiple laser beams may be used, each beam having the power described herein.

According to one embodiment, the energy density of the energy source is in the range of 1-6 J/mm ² . Energy density is the energy delivered by the energy source per unit area of the powder layer being printed.

According to one embodiment, the additive manufacturing method used is directed energy deposition (DED). This type of method uses an energy source to create a local melt pool. Metal powder is fed into this melt pool as a fill material. The position of the melt pool is constantly moving such that the solidified material creates a three-dimensional object. The energy source can be either a laser beam or a plasma arc. According to one embodiment, in a DED, the power of the laser source can be 50-2000W.

According to one embodiment, the DED method is performed in an inert shielding gas atmosphere that protects the melt pool. According to one embodiment, the material feed angle may vary depending on what a given molded object is.

According to one embodiment, an object manufactured by DED may be stress relieved. The stress relief temperature ranges from 650-1200° C. and depends on the volume of the manufactured object. Stress relief times vary from very short times such as 15 minutes to longer times such as several hours. According to one embodiment, pre-oxidation may be performed simultaneously with post-printing stress relief. The purpose of pre-oxidation is to form an aluminum oxide surface layer. According to one embodiment, said aluminum oxide layer has a thickness of at least 0.5 μm.

The additively manufactured object obtained from any of the methods/methods mentioned above or below may be post-processed.

Embodiments of the present disclosure are disclosed in more detail in connection with the following examples. Examples are to be considered illustrative and not limiting embodiments.

Example 1
Printing by SLM Gas atomization was used to make three powders (Powder 1-3) with chemical composition in wt% according to Table 1, then Powder 1 and Powder 3 and Force 4 within 10-45 μm and the powder 2 was sieved to an appropriate fraction such that the particle size was within 1-45 μm.

Several samples of different powders were printed as follows.

The powders described above were fed to the SLM machine by adding to the powder delivery system. During the printing process, powder was fed from the machine's powder delivery system and a scraper spread a layer of powder onto the build plate. The laser was then passed over the layer of powder according to the provided 3D drawing, whereby the powder layer was exposed to the laser beam and thus melted. After the layer of powder was melted, new layers were applied until the desired sample was formed according to the 3D drawing.

The thickness of the powder layer was 20-30 μm. Printing was done in an inert atmosphere with argon. The scanning speed was 500-800 mm/sec. The power of the energy source was 80-200W.

The sample was cooled to room temperature in an inert atmosphere. The powder on the printed sample was removed and then the build plate containing the sample was removed from the machine. The build plate with samples was heat treated at 650-1200° C. for 0.5-3 hours. The build plate and sample were then cooled to room temperature and then machined (cut) to remove the sample from the build plate.

Example 2
Printing by DED Gas atomization was used to produce two powders with compositions according to Table 2, which were then sieved into appropriate fractions to obtain powders within a particle size range of 45-90 μm.

Several samples from these powders in the form of cubic blocks were printed as follows.

A laser source was used to create a local melt pool. The powder was fed into a molten pool and rapidly solidified. Powder was added to the pool using a focused powder stream. The laser was moved along a predesigned path to create a layer of solidified substrate (in the XY plane). The laser was then moved up (Z-axis) and began creating a melt pool on the surface of the previous substrate, creating a new layer along a particular path. This produced a three-dimensional object.

The powder bed height was 0.3-2 mm. Printing was done with or without an argon atmosphere. The deposition rate was between 1000 mm/min and 2500 mm/min. Powder feed was from 4 g/min to 25 g/min. The power of the laser source was 50-2000W.

FIG. 3 discloses a photomicrograph of the DED printed structure of powder 5. FIG. The structure is very dense and shows no signs of cracking, defects or porosity. A Leica stereo microscope was used.

Example 3—Testing FIG. 1 shows a sample containing a conventionally made FeCrAl (CP1) alloy and a sample produced by additive manufacturing using an SLM (SLM1) and a sample using (SLM2). Figure 2 shows a comparison of creep strength with samples made by additive manufacturing.

Conventional specimens were prepared by casting and rolling and were measured by S.O.D. with diameter, _d0 , 4 mm and original gauge length, _L0 , 20 mm. S. Prepared according to EN ISO 6892-2:2018 "Cylindrical test pieces with threaded gripping ends".

Conventional samples had compositions according to the following specifications.

After printing, the additive manufacturing samples were printed using a standard S.I. S. Machined to EN ISO 6892-2:2018, edge gripped (turned), diameter d ₀ , 4 mm, original gauge length L ₀ , 20 mm. The additive manufacturing samples (SLM1 and SLM2) had compositions according to the following specifications.

A dead load was applied to the sample. Creep rate was calculated as the percentage change in length of the sample over time at constant load and temperature. Testing of printed samples was performed at 1100°C and 1200°C. A conventionally made sample (CP1) was tested at 900°C and 1100°C.

The printed material is found to be anisotropic. The creep results shown in FIG. 1 are for the stronger direction of the material with the sample loaded parallel to the printing direction. Furthermore, as can be seen from FIG. 1, the additively manufactured samples have a much lower creep rate compared to conventionally fabricated samples. Although the conventionally made sample was tested at a lower temperature, the creep rate was low and the creep strength of the printed sample was even higher. Additionally, the printed samples had a longer time to break, which means that such products have a longer lifespan.

FIG. 2 shows mass gain curves versus time at 1100° C. for an additively manufactured sample made from powder 4 of Table 1 and a conventionally produced sample having a similar composition to powder 4. Mass gain weight was checked at 100 hour intervals. The mass gain curve shows that the additively manufactured sample has better oxidation properties than the conventionally produced sample, meaning it is superior for high temperature applications and has a longer service life.

Claims (14)

A printable ferritic FeCrAl powder composition comprising:
The FeCrAl powder composition, in weight percent,
Cr 9.0-25.0,
Al 2.5-8.0,
Si≤3.0,
Mo ≤ 4.0,
Ni≤1.0,
Mn≤1.0,
C≦0.1,
S ≤ 0.01,
P≤0.01,
N≤0.1,
O≤0.2,
Ti≤1.7,
Y≤3.0,
Nb ≤ 3.3,
Zr ≤ 3.3,
V≤1.8
Ta + Hf ≤ 6.5
La ≤ 1.0,
Ce≤1.0,
The balance consists of Fe and inevitable impurities,
A printable ferritic FeCrAl powder composition, wherein the FeCrAl powder composition has a powder particle size distribution between 4-200 μm, such as between 10 μm and 120 μm. A printable FeCrAl powder composition according to claim 1, wherein the content of C is ≤ 0.05 wt%. 3. A printable FeCrAl powder composition according to claim 1 or claim 2, wherein the content of Mn is < 0.5 wt%. The printable FeCrAl powder composition content according to any one of claims 1 to 3, wherein the Si content is less than 0.5 wt% or greater than 0.5 to 3.0 wt%. A printable FeCrAl powder composition according to any one of claims 1 to 4, wherein the content of Al is 3-6 wt%. A printable FeCrAl powder composition according to any one of claims 1 to 5, wherein the Cr content is 9-11 wt% or 18-24 wt%. % by weight,
Cr 18-24,
Al 4-6,
Mn≤0.5,
Si ≤ 0.5 or more than 0.5 to 3,
Mo ≤ 0.5,
Ti≦0.5,
Y≤1.0,
Nb ≤ 0.5,
Zr≤0.5,
V≤0.5,
Ta + Hf ≤ 1.0,
La≤0.5,
Ce≤0.5,
The balance consists of Fe and inevitable impurities,
3. A printable FeCrAl powder composition according to claim 1 or claim 2. % by weight,
Cr 18-24,
Al 4-6,
Mn≤0.5,
Si ≤ 0.5 or more than 0.5 to 3,
Mo 1-4,
Ti≦0.5,
Y≤1.0,
Nb ≤ 0.5,
Zr≤0.5,
V≤0.5,
Ta + Hf ≤ 1.0,
La≤0.5,
Ce≤0.5,
The balance consists of Fe and inevitable impurities,
3. A printable FeCrAl powder composition according to claim 1 or claim 2. An additively manufactured object comprising the printable powder composition according to any one of claims 1-8. 10. The additively manufactured object of claim 9, wherein the object is a high temperature refractory heating element or high temperature refractory component. 10. The additively manufactured object of claim 9, wherein the object is an electrical heating element or an electrical resistance component. The method of claim 9-11, wherein the additive manufacturing method is selected from powder bed fusion additive manufacturing method or directed energy deposition (DED) and the ferritic FeCrAl powder according to any one of claims 1-9 is used. An additive manufacturing method for manufacturing an object according to any one of the preceding claims. 13. The additive manufacturing method of claim 12, wherein a powder bed fusion additive manufacturing method is used, and wherein the powder bed fusion additive manufacturing method is SLM or EBM. Use of an additively manufactured object according to any one of claims 9 to 13 as a component in electrical heating or high temperature applications or as a heating element.

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