Method for Manufacturing a Component by Means of Layered Construction

Abstract

The invention relates to a method for producing a component by means of layered construction, by combining a plurality of crystallites of a metallic material to form a single crystal. The single crystal is formed by thermomechanically activated successive anisotropic plastic deformation. The metallic material is heated during the construction of a new layer, with the result that the metallic material is melted in a linear region. The linear region is moved in order to construct the new layer.

Claims

1. A method for producing a component (1) by means of layered construction, comprising combining a plurality of crystallites of a metallic material to form a single crystal, wherein the single crystal is formed by thermomechanically activated successive anisotropic plastic deformation, wherein the metallic material is heated during the construction of a new layer, with the result that the metallic material is melted in a linear region, wherein mechanical stresses occur during melting and subsequent cooling, in particular solidification, of the metallic material, wherein the plastic deformation of the metallic material is caused by these mechanical stresses, wherein the mechanical stresses have a preferred direction because of the linear design of the melted linear region, whereby the anisotropic plastic deformation results, and wherein the new layer is gradually constructed by being traversed by the melted linear region, wherein the component is constructed layer by layer in a construction direction, wherein the linear region has a length (L) along its extension direction and a width (B) and a depth (D) which are both perpendicular to the extension direction of the linear region, wherein the ratio of length (L) and width (B) is at least 5:1, wherein the ratio of width (B) and depth (D) lies in a range of from 1:2 to 10:1, wherein the linear region is moved in order to construct the new layer, and wherein the linear region is subjected to a lateral movement perpendicular to its extension direction with a lateral speed v.sub.lat while maintaining its extension direction.

2. The method according to claim 1, wherein the ratio of length (L) and width (B) is at least 20:1.

3. The method according to claim 1, wherein the ratio of width (B) and depth (D) lies in a range of from 2:1 to 4:1.

4. The method according to claim 1, wherein the depth (D) of the linear region is in the range from 50 ?m to 1000 ?m.

5. The method according to claim 1, wherein the component is produced layer by layer by at least one of local melting of a powder layer of the metallic material or local application of the metallic material.

6. The method according to claim 1, wherein the metallic material in the linear region is melted by at least one of a laser or an electron beam.

7. The method according to claim 1, wherein the component or an installation space containing the component is additionally heated.

8. The method according to claim 1, wherein at least one of the metallic material, the component or the installation space is heated to a temperature (T) in the range of from 300? ? C. to 1200? C.

9. The method according to claim 1, wherein the layered construction is effected along a construction direction (4) and layers with thicknesses in the range of between 10 ?m and 500 ?m are generated.

10. The method according to claim 1, wherein the metallic material is formed of at least one of a nickel-based alloy, a nickel-titanium alloy or a copper alloy.

11. The method according to claim 1, wherein the lateral speed v.sub.lat is between 0.1 mm/s and 100 mm/s.

12. The method according to claim 11, wherein a crystal orientation of the single crystal is adjusted in a defined manner by adjustment of extension direction and lateral movement of the linear region in successive layers.

13. The method according to claim 1, wherein the extension direction of the linear region in successive layers is the same or is rotated by an angle corresponding to a rotational symmetry of the crystal lattice.

14. The method according to claim 1, wherein the direction of the lateral movement of the linear region in successive layers is the same or is rotated by an angle corresponding to a rotational symmetry of the crystal lattice.

15. The method according to claim 1, wherein the extension direction and the direction of the lateral movement of the linear region in successive layers, or in each case after a particular number of layers, are rotated by an equal angle value.

16. The method according to claim 1, further comprising at least one of the following: varying the extension direction of the linear region during the construction of the new layer, varying the lateral movement of the linear region during the construction of the new layer, varying the extension direction of the linear region in the construction direction, or varying the lateral movement of the linear region in the construction direction.

17. The method according to claim 1, wherein a linear region is melted only in subregions of the component.

18. The method according to claim 1, wherein monocrystalline and polycrystalline regions are produced in the component.

19. The method according to claim 1, wherein a continuous change in the crystal orientation is produced in the component.

20. A component comprising a single crystal with exactly adjusted primary and secondary crystal orientation, produced by a means of layered construction, comprising combining a plurality of crystallites of a metallic material to form a single crystal, wherein the single crystal is formed by thermomechanically activated successive anisotropic plastic deformation, wherein the metallic material is heated during the construction of a new layer, with the result that the metallic material is melted in a linear region, wherein mechanical stresses occur during melting and subsequent cooling, in particular solidification, of the metallic material, wherein the plastic deformation of the metallic material is caused by these mechanical stresses, wherein the mechanical stresses have a preferred direction because of the linear design of the melted linear region, whereby the anisotropic plastic deformation results, and wherein the new layer is gradually constructed by being traversed by the melted linear region, wherein the component is constructed layer by layer in a construction direction, wherein the linear region has a length (L) along its extension direction and a width (B) and a depth (D) which are both perpendicular to the extension direction of the linear region, wherein the ratio of length (L) and width (B) is at least 5:1, wherein the ratio of width (B) and depth (D) lies in a range of from 1:2 to 10:1, wherein the linear region is moved in order to construct the new layer, and wherein the linear region is subjected to a lateral movement perpendicular to its extension direction with a lateral speed v.sub.lat while maintaining its extension direction.

Description

[0091] The invention will now be explained in more detail with reference to embodiment examples. There are shown in

[0092] FIG. 1 a schematic representation of a component in production with a linear region,

[0093] FIG. 2 a schematic drawing of time curves of temperature, stress and plastic expansion in a heat-affected zone,

[0094] FIG. 3 a schematic representation of a formation of a monocrystalline component,

[0095] FIG. 4 an experimental example of a formation of a monocrystalline component,

[0096] FIG. 5 a schematic drawing with pole figures to describe the formation of a monocrystalline component as well as the rotation and the tilting of the crystal orientation.

[0097] FIG. 1 shows a schematic representation of a component 1 in production with a linear region 2. The component 1 is constructed layer by layer from a metallic material in an installation space inside a vacuum chamber. In order to construct a new layer, powder layers of the metallic material are preferably deposited as a powder bed with a doctor blade, heated by multiple scanning with an electron beam and selectively melted in the linear region 2. The thickness of the new layer is for example 50 ?m. The power of the electron beam is for example 1 kW. The installation space has an xy plane as construction plane and a z direction as construction direction. The dimension of the installation space is for example 300 mm in the construction plane and 300 mm in the construction direction.

[0098] The metallic material is melted in the linear region 2 by selective electron beam melting. The linear region 2 has a length L along its extension direction and a width B and a depth D which are each perpendicular to its extension direction. The depth D of the linear region is for example 500 ?m. The linear region 2 thus also penetrates into the ten layers produced directly before the new layer. The width B of the linear region is for example 1.5 mm. The length L of the linear region is for example 15 mm. The linear region 2 is surrounded by a heat-affected zone 3. The metallic material in the heat-affected zone 3 is not melted, more precisely is in part not yet melted, in part no longer melted. In the heat-affected zone 3, a temperature field generated by the electron beam acts in particular on the already solidified metallic material in layers produced directly before the new layer.

[0099] The linear region 2 is moved with a lateral speed v.sub.lat perpendicular to its extension direction. The lateral speed v.sub.lat is for example 5 mm/s.

[0100] A plastic deformation of the metallic material in the course of thermally induced mechanical stresses is caused by the melting and the subsequent solidification of the metallic material. The mechanical stresses are generated in a targeted manner by adjustment of the extension direction, speed and temperature of the linear region. The mechanical stresses exceed the yield point of the metallic material in particular in the linear region 2 and/or in the heat-affected zone 3. The mechanical stresses have a preferred direction because of the linear design of the linear region. The mechanical stress field is thus anisotropic. This anisotropy leads to the generation of a single crystal. The crystal orientation, in particular the primary and secondary crystal orientation, can be precisely adjusted by the mechanical stress field generated in a targeted manner by adjustment of extension direction, speed and temperature of the linear region.

[0101] FIG. 2 shows, in a schematic drawing, the temperature T, the mechanical stress in the y direction ?.sub.yy and the plastic expansion in the y direction ?.sub.yy in each case as a function of time t in the heat-affected zone 3. The construction temperature is labeled T.sub.B. In the construction plane, i.e. in the xy plane, the symmetry is broken with respect to the mechanical stress and the plastic expansion. This symmetry breaking, coupled with the property of crystals to align in particular directions due to plastic deformation, which is called texture formation, ultimately leads to the controlled alignment of each individual columnar crystal and finally to the generation of the single crystal.

[0102] FIG. 3 shows a schematic representation of a formation of a monocrystalline component. In it, the alignment of individual crystallites at different construction heights during the construction of a component is visualized. The construction direction 4 is perpendicular to the paper plane, thus runs in the z direction. The extension direction of the linear region 2 lies in the paper plane and, alternating from layer to layer, is parallel to the x axis in a first layer, parallel to the y axis in a second layer, and so on. The movement direction of the linear region 2 moved with the lateral speed v.sub.lat perpendicular to its extension direction changes by 90? clockwise from layer to layer. The primary crystal orientation is already precisely adjusted after a few 100 ?m construction height: the individual crystallites are in each case aligned in the z direction, i.e. in the direction. At 1 mm the secondary crystal orientation is still isotropic. With increasing construction height, each individual crystallite is rotated little by little to an angular position with respect to the x axis of 45?, i.e. the secondary crystal orientation is also precisely adjusted. Between a construction height of 5 mm and 15 mm the high-angle grain boundaries (represented by continuous lines) disappear. Only low-angle grain boundaries (represented by dotted lines) persist. The crystallites are therefore finally melted completely to form a single crystal at a construction height of 15 mm.

[0103] FIG. 4 shows an experimental example of a formation of a monocrystalline component 1. The specific example involves a nickel-based single crystal alloy of the CMSX-4 type. The production is effected by selective electron beam melting. A section of the rod-shaped component 1 is depicted in the lower part of FIG. 4. The construction direction 4 represented by an arrow goes from right to left. The gray tones show different crystal orientations. High-angle grain boundaries are characterized by black lines. In the upper part of FIG. 4, by way of example, three sections of the rod-shaped component are represented enlarged. The enlarged section shown on the right relates to the first 2 mm in the construction direction 4. In it, many different crystal orientations with high-angle grain boundaries lying in between are still to be observed. The enlarged section shown in the middle relates to a construction height of from approximately 5 to 7 mm in the construction direction 4. Here, the crystal orientation has already converged in larger regions. The high-angle grain boundaries disintegrate more and more with advancing construction height. The enlarged section shown on the left relates to a construction height of from approximately 22 to 24 mm in the construction direction 4. Here, the crystal orientation has largely converged. The high-angle grain boundaries are disintegrated for the most part. The disappearance of the high-angle grain boundaries shows the melting to form the single crystal.

[0104] FIG. 5 shows a schematic drawing with pole figures to describe the formation (a) of a monocrystalline component 1 as well as the rotation (b) of the secondary crystal orientation and the tilting (c) of the primary crystal orientation of the monocrystalline component 1. A rod-shaped component 1 is shown schematically in a left-hand column. The construction direction 4 runs from the bottom to the top in the z direction, represented by a vertical arrow in the figure. One pole figure is represented in each case for four different construction heights. The four different construction heights are marked in each case by a horizontal arrow. The single crystal selection is represented in the next column (a) starting from an isotropic distribution in the bottom pole figure to a development of precisely defined positions in the top pole figure. A monocrystalline state is already precisely adjusted in the top pole figure of column (a). Starting from this monocrystalline state the secondary crystal orientation can be changed in a targeted manner. The crystal lattice can thus be rotated in the xy plane. This is visualized in column (b) with reference to four further pole figures. The bottom pole figure corresponds to the top pole figure of column (a). To rotate the crystal lattice, the scanning direction of the electron beam and thus the extension direction of the linear region 2 is rotated in the xy plane by for example 0.5?+90? per layer. Starting from the state in the bottom pole figure, the secondary crystal orientation in column (b) is rotated successively by 45? up to the top pole figure. After that, the primary crystal orientation is changed in a targeted manner in column (c). The single crystal is tilted with respect to the z direction. This is visualized in column (c) with reference to four further pole figures. The bottom pole figure there corresponds to the top pole figure of column (b). The tilting of the single crystal is effected by symmetry breaking. A symmetry breaking can be achieved by the extension direction of the linear region 2 and its movement direction remaining the same in successive layers.

[0105] Even if the portions in which the component 1 still does not have a monocrystalline state in an initial phase of the production method are nevertheless already called component 1 here, it is self-evident that preferably only the portions after single crystal selection has been effected finally form the component 1. For this, the portions from the initial phase of the production method can be detached from the component 1.

LIST OF REFERENCE NUMBERS

[0106] 1 component [0107] 2 linear region [0108] 3 heat-affected zone [0109] 4 construction direction [0110] L length [0111] B width [0112] D depth [0113] ?.sub.yy mechanical stress in the y direction [0114] ?.sub.yy plastic expansion in the y direction [0115] T temperature [0116] T.sub.B construction temperature