Method for manufacturing a shaped body and shaped body

Abstract

To provide a shaped body manufacturing method that can reduce cracks formed in the shaped body manufactured through powder bed fusion using a powder made of a gamma prime precipitation-strengthened-type Ni-based alloy.SOLUTION: The present invention discloses a method for manufacturing a shaped body through powder bed fusion using a powder made of a gamma prime precipitation-strengthened-type Ni-based alloy, wherein the Ni-based alloy contains, in terms of mass percentage, 7.0-17.0% of Cr, 7.0-12.0% of Co, 5.0-8.0% of Al+Ti, 2.0-12.0% of W, 1.5-4.4% of Nb+Ta, 2.3% or less of Mo, 0.3% or less of C, 2.0% or less of Hf, and 0.2% or less of Zr, and when applying a laser onto a layer 3 formed of powder along a plurality of scanning lines 4 parallel to each other, a value found by dividing the interval between the scanning lines 4 by a laser spot diameter is 0.2-1.1.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a shaped body and a shaped body obtained by the method.

Background Art

[0002] Conventionally, a method for manufacturing a shaped body by powder bed fusion using a powder composed of a Ni-based alloy has been known. A shaped body made of a Ni-based alloy manufactured by such a manufacturing method is used as a high-temperature component such as a gas turbine engine.

[0003] As the Ni-based alloy constituting the powder, a gamma prime precipitation-strengthened Ni-based alloy may be used. The gamma prime precipitation-strengthened Ni-based alloy is a Ni-based alloy whose composition is adjusted so that a gamma prime (Ni3(Al,Ti)) phase for strength strengthening precipitates when the manufactured shaped body is heat-treated.

[0004] Regarding Ni-based alloys containing Al and Ti, it is known that when the sum of twice the Al content and the Ti content (2Al + Ti) is 6% or more, cracks are likely to occur during welding. In powder bed fusion, for example, microcracks having a length of several micrometers to more than several hundred micrometers can be formed in the manufactured shaped body.

[0005] As a technique for suppressing the occurrence of cracks during welding of a gamma prime precipitation-strengthened Ni-based alloy, for example, Patent Document 1 describes restricting the Si content and the Zr content to less than 0.03% by mass percentage, respectively.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] In contrast, regardless of whether or not the Si content and Zr content in the Ni-based alloy are restricted, it is desired to suppress the generation of cracks during welding of the gamma-prime precipitation-strengthened Ni-based alloy, and in particular, to reduce the cracks formed in the shaped body manufactured by powder bed fusion.

[0008] Therefore, an object of the present invention is to provide a method for manufacturing a shaped body capable of reducing cracks formed in a shaped body manufactured by powder bed fusion using a powder composed of a gamma-prime precipitation-strengthened Ni-based alloy, and a shaped body obtained by this method for manufacturing a shaped body.

Means for Solving the Problems

[0009] In order to solve the above problems, as a result of intensive research, the inventors of the present invention have found that there is a relationship between the value obtained by dividing the interval between those scanning lines by the laser spot diameter in powder bed fusion in which a laser is irradiated along a plurality of scanning lines parallel to each other on a layer composed of powder and the formation of cracks in the shaped body. The present invention has been made from such a viewpoint.

[0010] That is, the method for manufacturing a shaped body of the present invention is a method for manufacturing a shaped body by powder bed fusion using a powder composed of a gamma-prime precipitation-strengthened Ni-based alloy, The Ni-based alloy contains, in mass percentage, 7.0 to 17.0% of Cr, 7.0 to 12.0% of Co, 5.0 to 8.0% of Al + Ti, 2.0 to 12.0% of W, 1.5 to 4.4% of Nb + Ta, 2.3% or less of Mo, 0.3% or less of C, 2.0% or less of Hf, and 0.2% or less of Zr. When irradiating a laser along a plurality of scanning lines parallel to each other on the layer composed of the powder, the value obtained by dividing the interval between the plurality of scanning lines by the laser spot diameter is 0.2 or more and 1.1 or less.

[0011] According to the above configuration, cracks formed in the shaped body can be reduced.

[0012] Further, the shaped body of the present invention is a shaped body made of a Ni-based alloy and containing a dendritic crystal structure, and the Ni-based alloy contains, by mass percentage, 7.0 to 17.0% of Cr, 7.0 to 12.0% of Co, 5.0 to 8.0% of Al + Ti, 2.0 to 12.0% of W, 1.5 to 4.4% of Nb + Ta, 2.3% or less of Mo, 0.3% or less of C, 2.0% or less of Hf, and 0.2% or less of Zr. The spacing between the branches of the primary dendritic crystal of the dendritic crystal structure is less than 3 μm, and the maximum value of the pole density of the pole figure measured by the EBSD method is 5 or more.

[0013] Here, the "pole density of the pole figure" is obtained by calculating how many times each crystal orientation in the measurement plane appears when the state where all crystal orientations appear with a uniform density (i.e., a completely randomly oriented structure) is used as a reference, and is calculated as MUD (Multiples of a Uniform Density) by analysis with software attached to the EBSD device. The larger the MUD, the more the crystal orientation of the measurement plane is biased toward a specific crystal plane.

[0014] As a method for manufacturing a casting with a large MUD by casting, unidirectional solidification casting, single crystal casting, etc. are known, but in those castings, the spacing between the branches of the primary dendritic crystal of the dendritic crystal structure is as large as more than about 40 μm. On the other hand, in a shaped body manufactured by powder bed fusion using a laser as a heat source, the spacing between the branches of the primary dendritic crystal of the dendritic crystal structure is as small as less than 3 μm. Further, as described above, if the value obtained by dividing the spacing between a plurality of scanning lines by the laser spot diameter in powder bed fusion is 0.2 or more and 1.1 or less, the maximum value of the pole density (i.e., MUD) of the pole figure measured by the EBSD method becomes 5 or more. Therefore, the shaped body having the above configuration is a shaped body with few cracks.

Advantages of the Invention

[0015] According to the present invention, it is possible to reduce cracks formed in a formed body manufactured by powder bed fusion using a powder composed of a gamma prime precipitation strengthened Ni-based alloy.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0017] The method for manufacturing a formed body according to an embodiment of the present invention is a method for manufacturing a formed body by powder bed fusion using a powder composed of a gamma prime precipitation strengthened Ni-based alloy. In powder bed fusion, the heat source for melting the powder may be an electron beam in some cases, but in this embodiment, the heat source is a laser.

[0018] In powder bed fusion, as shown in FIG. 1, a layer 3 made of powder is formed on a platform 1, and a laser is irradiated along a plurality of scanning lines 4 parallel to each other on the layer 3. The laser is irradiated so as to be focused near the surface of the layer 3. The position, shape, and length of each scanning line 4 are determined by the cross-sectional shape of the formed body to be manufactured. For example, the scanning line 4 may be a straight line or a curve.

[0019] FIG. 1 is an example of manufacturing a rectangular prism-shaped formed body. In FIG. 1, the scanning directions of the laser are opposite to each other for adjacent scanning lines 4, but the scanning directions of the laser may be the same for all scanning lines 4.

[0020] By irradiating layer 3 with a laser, part or all of layer 3 is melted and solidified. Then, the platform 1 is lowered by the thickness of layer 3, a new layer (hereinafter, the uppermost layer) 3 made of powder is formed on the immediately preceding layer (hereinafter, the immediately preceding layer) 3, and the uppermost layer 3 is irradiated with a laser along a plurality of scanning lines 4 parallel to each other. Note that the bed 2 includes the already formed portion where the uppermost layer 3 is formed on the immediately preceding layer 3 and the unmelted powder.

[0021] In the uppermost layer 3 and the immediately preceding layer 3, the directions of the scanning lines 4 may be the same or different. When the directions of the scanning lines 4 in the uppermost layer 3 and the immediately preceding layer 3 are different, the angle of the scanning line 4 in the uppermost layer 3 with respect to the scanning line 4 in the immediately preceding layer 3 (hereinafter, the scanning rotation angle) can be determined as appropriate. For example, in FIG. 1, the scanning rotation angle is 90 degrees.

[0022] By repeating the above operations and finally removing the unmelted powder from the bed 2, a shaped body is manufactured. In such a shaped body, the spacing between the branches of the primary dendrites of the dendritic crystal structure is less than 3 μm.

[0023] The particle size distribution of the powder used in powder bed fusion is, for example, 5 to 75 μm, but preferably 15 to 63 μm. The thickness of each layer 3 is, for example, 20 to 60 μm.

[0024] The Ni-based alloy constituting the powder contains, as essential components other than Ni, 7.0 to 17.0% of Cr, 7.0 to 12.0% of Co, 5.0 to 8.0% of Al + Ti, 2.0 to 12.0% of W, and 1.5 to 4.4% of Nb + Ta by mass percentage (hereinafter the same). Examples of such Ni-based alloys include IN738C (IN is an abbreviation of Inconel (registered trademark), the same hereinafter), IN738LC, CM247LC, Mar-M247, etc. Note that with respect to Nb and Ta, the Ni-based alloy may not contain either Nb or Ta.

[0025] The content of each essential component is more preferably Cr: 7.0 - 10.0%, Co: 8.0 - 11.0, Al + Ti: 5.0 - 7.5%, W: 8.0 - 11.0%, Nb + Ta: 2.0 - 4.0%.

[0026] As other optional components, the Ni-based alloy may contain at least one of Mo of 2.3% or less (preferably 0.2 - 1.0%), C of 0.3% or less (preferably 0.01 - 0.2%), Hf of 2.0% or less (preferably 0.5 - 2.0%), and Zr of 0.2% or less. The balance other than the above-described components of the Ni-based alloy is Ni and inevitable impurities.

[0027] In this embodiment, when irradiating the laser on each layer 3, the value (L / D) obtained by dividing the interval L between the scanning lines 4 by the laser spot diameter D is set to be 0.2 or more and 1.1 or less. The laser spot diameter D is the beam diameter at the position where the laser intensity has dropped from the peak value to 1 / e 2 (in other words, the position where it becomes about 13.5% of the peak value). Some powder bed fusion devices using a laser can have the laser spot diameter set by the device user, while others cannot.

[0028] The laser spot diameter D is, for example, 0.02 - 0.20 mm, but preferably 0.05 - 0.15 mm. The interval L between the scanning lines 4 is, for example, 0.03 mm - 0.08 mm.

[0029] The laser scanning speed is, for example, 500 - 3000 mm / s, but preferably 600 - 2000 mm / s, and more preferably 700 - 1500 mm / s. The laser output is, for example, 100 - 400 W, but preferably 130 - 350 W, and more preferably 150 - 300 W.

[0030] By setting the value (L / D) obtained by dividing the interval L between the scanning lines 4 when irradiating the laser on each layer 3 as described above by the laser spot diameter D to be 0.2 or more and 1.1 or less, cracks formed in the shaped body can be reduced. And in the shaped body with few cracks manufactured in this way, the maximum value of MUD (the pole density of the positive pole figure measured by the EBSD method) is 5 or more (10 or more depending on the conditions).

Example

[0031] Hereinafter, the present invention will be described by way of examples, but the present invention is not limited to the following examples.

[0032] (Example 1) A cubic shaped body with a side length of 10 mm was manufactured by powder bed fusion using powder having alloy components equivalent to CM247LC. The particle size distribution of the powder was 16 to 45 μm. Also, when analyzing the alloy components of the powder, the contents of components other than Ni were Cr: 8.0%, Co: 9.1%, Al: 5.5%, Ti: 0.7%, W: 9.5%, Nb: 0%, Ta: 3.1%, Mo: 0.5%, C: 0.06%, Hf: 1.5%, Zr: 0.01% (the contents of inevitable impurities are omitted).

[0033] As the powder bed fusion apparatus, EOS M290 manufactured by EOS was used. In this apparatus, the laser spot diameter D is set to 0.08 mm on the manufacturer's side. When manufacturing the shaped body, the thickness of each layer was 40 μm, the interval between the scanning lines when irradiating the laser on each layer was 0.03 mm, the laser scanning speed was 1000 mm / s, the laser output was 180 W, and the scanning rotation angle was 90 degrees.

[0034] (Example 2) A shaped body was manufactured in the same manner as in Example 1 except that the interval between the scanning lines when irradiating the laser on each layer was 0.04 mm.

[0035] (Example 3) A shaped body was manufactured in the same manner as in Example 1 except that the interval between the scanning lines when irradiating the laser on each layer was 0.05 mm.

[0036] (Example 4) A shaped body was manufactured in the same manner as in Example 1, except that the interval between the scanning lines when irradiating the laser on each layer was set to 0.06 mm.

[0037] (Example 5) A shaped body was manufactured in the same manner as in Example 4, except that the scanning rotation angle was set to 67 degrees.

[0038] (Example 6) A shaped body was manufactured in the same manner as in Example 1, except that the interval between the scanning lines when irradiating the laser on each layer was set to 0.07 mm.

[0039] (Example 7) A shaped body was manufactured in the same manner as in Example 1, except that the interval between the scanning lines when irradiating the laser on each layer was set to 0.08 mm.

[0040] (Comparative Example 1) A shaped body was manufactured in the same manner as in Example 1, except that the interval between the scanning lines when irradiating the laser on each layer was set to 0.09 mm.

[0041] (Comparative Example 2) A shaped body was manufactured in the same manner as in Example 1, except that the interval between the scanning lines when irradiating the laser on each layer was set to 0.10 mm.

[0042] The manufacturing conditions of the shaped bodies of Examples 1 to 7 and Comparative Examples 1 and 2 are shown in Table 1. Table 1 also shows the value (L / D) when the interval L between the scanning lines is divided by the laser spot diameter D.

[0043]

Table 1

[0044] (Test) The shaped bodies of Examples 1 to 7 and Comparative Examples 1 and 2 were cut along a plane orthogonal to the stacking direction (the vertical direction in FIG. 1), and micrographs of the cut surfaces were taken. FIG. 3 is a micrograph of Example 5, and FIG. 4 is a micrograph of Comparative Example 1. Then, the crack length per unit area observed on the cut surface in each of Examples 1 to 7 and Comparative Examples 1 and 2 was calculated as the crack amount.

[0045] Further, for each of Examples 1 to 7 and Comparative Examples 1 and 2, the pole density of the positive pole figure was measured by the EBSD method on the cut surface obtained by cutting the shaped body along a plane orthogonal to the stacking direction. For this measurement, an SEM-SU5000 manufactured by Hitachi, Ltd. and a Pegasus Digiview5 manufactured by EDAX / TSL were used as the EBSD apparatus.

[0046] Regarding the measurement of the pole density of the positive pole figure, more specifically, as a pre-treatment, the cut surface was mechanically polished using waterproof abrasive paper and diamond abrasive grains, and then polished to a finish using colloidal silica. This pre-treatment is for reducing measurement defects and ensuring measurement accuracy, and is generally used for EBSD measurement. Next, Kikuchi lines were measured at a step size of 3 μm for a region of 900 μm × 900 μm on the cut surface, and analyzed using analysis software (OIM Data Collection / OIM Analysis ver.8 manufactured by EDAX / TSL) to obtain a {100} pole figure in which the {100} poles were projected. The MUD was calculated from the positive pole figure. In calculating the MUD, the spherical harmonic function method was used, with a development order of 16 and a half-value width of 5 degrees.

[0047] The maximum values of MUD and the crack amounts of Examples 1 to 7 and Comparative Examples 1 and 2 are shown in Table 2. Also, the maximum values of MUD and the crack amounts of Examples 1 to 7 and Comparative Examples 1 and 2 are shown graphically in FIG. 2.

[0048]

Table 2

[0049] As is clear from Table 2 and FIG. 2, in Comparative Examples 1 and 2 where the interval between scanning lines when irradiating the laser on each layer was made larger than 0.09 mm, that is, L / D was made larger than 1.1, the amount of cracks was large. On the other hand, in Examples 1 to 7 where the interval between scanning lines when irradiating the laser on each layer was adjusted so that L / D was 0.2 or more and 1.1 or less, the amount of cracks was small.

[0050] Also, in Comparative Examples 1 and 2, the maximum value of MUD was less than 5, whereas in Examples 1 to 7, the maximum value of MUD was 5 or more. Therefore, a shaped body with a maximum value of MUD of 5 or more is a shaped body with few cracks.

Explanation of Signs

[0051] 1 Platform 2 Bed 3 Layer 4 Scanning Line

Claims

1. A method for manufacturing a shaped body by powder bed fusion using a powder composed of a gamma prime precipitation strengthened Ni-based alloy, wherein the Ni-based alloy contains, by mass percentage, 7.0 to 10.0% Cr, 8.0 to 11.0% Co, 5.0 to 7.5% Al + Ti, 8.0 to 11.0% W, 2.0 to 4.0% Nb + Ta, 0.2 to 1.0% Mo, 0.01 to 0.2% C, 0.5 to 2.0% Hf, and 0.2% or less Zr, with the balance being Ni and unavoidable impurities; when irradiating a laser along a plurality of scanning lines parallel to each other on a layer composed of the powder, the value obtained by dividing the interval between the plurality of scanning lines by the laser spot diameter is 0.2 or more and 1.1 or less; A method for manufacturing a shaped body.

2. A shaped body made of a Ni-based alloy and including a dendritic crystal structure, wherein the Ni-based alloy contains, by mass percentage, 7.0 to 10.0% Cr, 8.0 to 11.0% Co, 5.0 to 7.5% Al + Ti, 8.0 to 11.0% W, 2.0 to 4.0% Nb + Ta, 0.2 to 1.0% Mo, 0.01 to 0.2% C, 0.5 to 2.0% Hf, and 0.2% or less Zr, with the balance being Ni and unavoidable impurities; the interval between the branches of the primary dendrites of the dendritic crystal structure is less than 3 μm; A shaped body having a maximum value of pole density of a positive pole figure measured by the EBSD method of 5 or more.

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